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C-Kermit 8.0 Update Notes

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Second Supplement to Using C-Kermit, 2nd Edition

For C-Kermit 8.0

As of C-Kermit version: 8.0.211
Date of C-Kermit release: 10 April 2003
This file last updated: Mon Jan 20 11:22:18 2014

Authors: Frank da Cruz and Christine M. Gianone
Address: The Kermit Project
         Columbia University
         612 West 115th Street
         New York NY 10025-7799
         USA
Fax:     +1 (212) 662-6442
E-Mail:  support@kermitproject.org
Web:     http://www.kermitproject.org/
Or:      http://www.kermit-project.org/
Or:      http://www.columbia.nyc.ny.us/kermit/

(Note, none of the above is valid after June 30, 2011.)

NOTICES

This document:
Copyright © 1997, 2002, Frank da Cruz and Christine M. Gianone. All rights reserved.

Kermit 95:
Copyright © 1995, 2002, Trustees of Columbia University in the City of New York. All rights reserved.

C-Kermit:
Copyright © 1985, 2002,
Trustees of Columbia University in the City of New York. All rights reserved. See the C-Kermit COPYING.TXT file or the copyright text in the ckcmai.c module for disclaimer and permissions.

When Kerberos(TM) and/or SRP(TM) (Secure Remote Password) and/or SSL/TLS protocol are included:
Portions Copyright © 1990, Massachusetts Institute of Technology.
Portions Copyright © 1991, 1993 Regents of the University of California.
Portions Copyright © 1991, 1992, 1993, 1994, 1995 by AT&T.
Portions Copyright © 1997, Stanford University.
Portions Copyright © 1995-1997, Eric Young <eay@cryptosoft.com>.

For the full text of the third-party copyright notices, see Appendix V.

WHAT IS IN THIS FILE

This file lists changes made to C-Kermit since version 7.0 was released in January 2000. Use this file as a supplement to:

until the third edition of Using C-Kermit is published. We apologize for the scattered documentation and will consolidate it when we are able.

ADDITIONAL FILES

Several other files accompany this new Kermit release:

ckututor.html
C-Kermit Tutorial (for Unix). Also distributed in Nroff form as ckuker.nr, the Unix C-Kermit manual page.

security.htm
Discussion of Kermit's new authentication and encryption features, updated for C-Kermit 8.0.

telnet.htm
Detailed documentation of Kermit's Telnet client, updated for C-Kermit 8.0.

ftpscripts.html
Tutorial: Writing FTP automation scripts

ckcbwr.html
Platform-independent C-Kermit hints and tips. Also distributed in plain text form as ckcbwr.txt

ckubwr.html
Unix-specific C-Kermit hints and tips. Also distributed in plain text form as ckubwr.txt.

ckvbwr.html
VMS-specific C-Kermit hints and tips. Also distributed in plain text form as ckvbwr.txt.

ckuins.html
Unix C-Kermit installation instructions. Also distributed in plain text form as ckuins.txt.

ckvins.html
VMS C-Kermit installation instructions. Also distributed in plain text form as ckvins.txt.

ckccfg.html
Compile-time configuration options. Also distributed in plain text form as ckccfg.txt.

ckcplm.html
C-Kermit Program Logic Manual. Also distributed in plain text form as ckcplm.txt.

iksd.html
Internet Kermit Service Administrators Guide for Unix.

skermit.html
C-Kermit as an SSH Subsystem (SFTP server replacement).

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CONTENTS

  0. WHAT'S NEW
  1. FIXES SINCE VERSION 7.0.196
  2. SSH AND HTTP
      2.1. SSH Connections
      2.2. HTTP Connections
         2.2.1. HTTP Command Switches
         2.2.2. HTTP Action Commands
         2.2.3. HTTP Headers
         2.2.4. Secure HTTP Connections
         2.2.5. HTTP Variables
         2.2.6. The HTTP Command-Line Personality
  3. THE BUILT-IN FTP CLIENT
      3.1. Making and Managing FTP Connections
         3.1.1. Kermit Command-Line Options for FTP
         3.1.2. The FTP Command-Line Personality
         3.1.3. The FTP URL Interpreter
         3.1.4. Interactive FTP Session Establishment
      3.2. Making Secure FTP Connections
      3.3. Setting FTP Preferences
      3.4. Managing Directories and Files
      3.5. Uploading Files With FTP
         3.5.1. FTP PUT Switches
         3.5.2. Update Mode
         3.5.3. Recovery
      3.6. Downloading Files With FTP
         3.6.1. FTP GET Switches
         3.6.2. Filename Collisions
         3.6.3. Recovery
      3.7. Translating Character Sets
         3.7.1. Character Sets and Uploading
         3.7.2. Character Sets and Downloading
      3.8. FTP Command Shortcuts
      3.9. Dual Sessions
      3.10. Automating FTP Sessions
         3.10.1. FTP-Specific Variables and Functions
         3.10.2. Examples
         3.10.3. Automating Secure FTP Connections
      3.11. Advanced FTP Protocol Features
 4. FILE SCANNING
 5. FILE AND DIRECTORY NAMES CONTAINING SPACES
 6. OTHER COMMAND PARSING IMPROVEMENTS
      6.1. Grouping Macro Arguments
      6.2. Directory and File Name Completion
      6.3. Passing Arguments to Command Files
      6.4. More-Prompting
      6.5. Commas in Macro Definitions
      6.6. Arrow Keys
 7. NEW COMMANDS AND SWITCHES
 8. SCRIPTING IMPROVEMENTS
      8.1. Performance and Debugging
      8.2. Using Macros as Numeric Variables
      8.3. New IF Conditions
      8.4. The ON_UNKNOWN_COMMAND and ON_CD Macros
      8.5. The SHOW MACRO Command
      8.6. Arrays
      8.7. New or Improved Built-in Variables and Functions
      8.8. The RETURN and END Commands
      8.9. UNDEFINing Groups of Variables
      8.10. The INPUT and MINPUT Commands
      8.11. Learned Scripts
      8.12. Pattern Matching
      8.13. Dates and Times
      8.14. Trapping Keyboard Interruption
 9. S-EXPRESSIONS
      9.1. What is an S-Expression?
      9.2. Integer and Floating-Point-Arithmetic
      9.3. How to Use S-Expressions
      9.4. Summary of Built-in Constants and Operators
      9.5. Variables
      9.6. Assignments and Scope
      9.7. Conditional Expressions
      9.8. Extensibility
      9.9. Examples
      9.10. Differences from Algebraic Notation
      9.11.Differences from Lisp
 10. FILE TRANSFER
 11. MODEMS AND DIALING
 12. TERMINAL CONNECTION
 13. CHARACTER SETS
 14. DIALOUT FROM TELNET TERMINAL SERVERS
 15. COPING WITH BROKEN KERMIT PARTNERS
 16. NEW COMMAND-LINE OPTIONS
 17. LOGS

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0. WHAT'S NEW

The Initialization and Customization Files
C-Kermit 8.0 now supports specification of the initialization file name (path) in an environment variable, CKERMIT_INI. It also relies far less than before on the initialization for functioning. See Section 5 of the Unix C-Kermit installation instructions for details. As of version 8.0.201, C-Kermit also executes your customization file (if you have one) even if the initialization file was not found. Previously, the customization file was executed by a TAKE command in the initialization file (and it still is, if an initialization is found).

Incompatible Changes
As always, we do our best to avoid changes that break existing scripts. However, C-Kermit 8.0 does include a rather pervasive syntax change that might alter the behavior of scripts that depend on the previous behavior. As described in Section 5, C-Kermit now accepts doublequotes in most contexts where you previously had to use braces to group multiple words into a single field, or to force inclusion of leading or trailing blanks. Most noticeably, in C-Kermit 7.0 and earlier:

  echo {this is a string}

would print:

  this is a string

whereas:

  echo "this is a string"

printed:

  "this is a string"

In C-Kermit 8.0, both print:

  this is a string

To force the doublequotes to be treated as part of the string, use either of the following forms:

  echo {"this is a string"}
  echo ""this is a string""

Similarly, to force braces to be treated as part of the string:

  echo "{this is a string}"
  echo {{this is a string}}

Other incompatibilities:

  1. Using the SET HOST command to make HTTP connections is no longer supported. Instead, use the new HTTP OPEN command, described in Section 2.2.

C-Kermit 7.1 Alpha.01 (8 December 2000)
  • Its major new features are those listed in the Table of Contents: the FTP client, file scanning, command parsing and scripting improvements, S-Expressions, and support for the Telnet Com Port Option, plus wider availability of the Kerberos, SSL/TLS, and SRP security options for secure Internet connections.

    C-Kermit 7.1.199 Alpha.02 (4 January 2001)
    • C-Kermit now accepts FTP, TELNET, and IKSD URLs as its first command-line argument.
    • Character-set translation added to the FTP client for filenames.
    • Optional setting of date of incoming files by FTP [M]GET from the server date.
    • FTP CHECK filename added to let FTP client check the existence of a file on the server.
    • FTP GET /NAMELIST:filename added to get list of server filenames into a local file.
    • FTP [M]PUT /SERVER-RENAME:template added to make server rename a file as indicated by the template after it has arrived completely.
    • FTP [M]GET /SERVER-RENAME:template added to make server rename a file as indicated by the template after it has been sent completely.
    • FTP VDIRECTORY added for getting verbose directory listings from TOPS-20.
    • FTP TYPE TENEX added for transferring 8-bit binary files with PDP-10s.
    • Added automatic text/binary mode switching for FTP [M]GET, based on filename patterns (e.g. *.zip, *.gz, *.exe are binary; *.txt, *.c are text).
    • SET SEND I-PACKETS OFF added for coping with Kermit servers that do not support I packets.
    • A new option was added to \fword() and \fsplit() for parsing comma-separated lists that might contain empty elements.
    • Bug fixes including:
      • {} or "" could not be used as expected to represent the empty string.
      • ,- on a line by itself in a macro definition caused subsequent statements to be skipped.
      • FTP [M]GET didn't work right if path segments were included in the filespec.
      • FTP MGET, if interrupted, did not clear its file list.
      • Various problems with FTP PUT /AS-NAME that nobody noticed.
      • Some FTP messages and displays interfered with each other.
      • Parsing of YESTERDAY, TODAY, and TOMORROW in date-time fields was broken.
      • Automatic old-to-new dialing directory format conversion was broken on VMS.
      • Various source-code portability problems fixed.
    • Improvement of various HELP and SHOW messages.

    C-Kermit 7.1.199 Alpha.04 (1 April 2001)
    • Big changes:
      • Changed default modem type from NONE to GENERIC.
      • Generic dialing now sends no init string at all.
      • Changed default terminal bytesize from 7 to 8.
    • New features:
      • SET SESSION-LOG TIMESTAMPED-TEXT for timestamped session log.
    • New modem types:
      • Conexant modem family
      • Lucent VENUS chipset
      • PCTel V.90 chipset
      • Zoom V.90
      • Zoom V.92
    • FTP client:
      • FTP OPEN /PASSIVE and /ACTIVE switches added.
      • Now works with servers that that don't include path in NLST response.
      • Fixed SEND /RECURSIVE not to follow symlinks (UNIX).
      • SET FTP VERBOSE-MODE default is now OFF instead of ON.
    • Kermit protocol:
      • Fixed what I hope is the last "Receive window full" error.
      • SET PREFIXING or SET CONTROL PREFIX now automatically sets CLEARCHANNEL OFF.
      • Fixed incorrect report of number of files transferred at end of transfer.
      • Fixed SEND /RECURSIVE not to follow symlinks (UNIX).
    • UNIX:
      • HTTP and shadow passwords enabled for SCO 5.0.6.
      • Even with SET FILENAMES CONVERTED, spaces were still accepted in incoming filenames; now they are converted to underscores.
      • Added support for compile-time mktemp()/mkstemp() selection.
    • VMS:
      • Session-log format for scripted sessions fixed.
    • Scripting:
      • Fixed \frdir() not to follow symlinks (UNIX).
      • Fixed \fday() not to dump core for dates prior to 17 Mar 1858.
    • General:
      • "Closing blah..." message upon exit could not be suppressed.
      • Added /PAGE and /NOPAGE to DELETE switches.
      • Added GO response for DELETE /ASK (delete all the rest without asking).
      • Added GO response to "more?" prompt (for multi-page screen output).
      • Updated HELP texts.

    C-Kermit 7.1.199 Beta.01 (10 May 2001)
    • FTP client verbosity adjustments.
    • Bug with generic modem dialing pausing several secs fixed.
    • SET HOST /USER:, SET LOGIN USERID, etc, fixed when given no user ID.
    • A couple \v(dm_blah) dial modifier variables added.
    • "--version" command-line switch added.
    • Fixed NetBSD serial-port DTR handling.
    • Lots of syntax cleanups for Flexelint and gcc -Wall.
    • Fixed modem-type aliases to not take precedence over real names.
    • Fixed funny treatment of doublequotes by ECHO command.
    • Enabled SET SESSION-LOG for VMS and other non-UNIX platforms.
    • Fixed changing direction in command history buffer.
    • Fixed handling of IKSD URLs.
    • Made sure DELETE prints a message if it got any errors.

    C-Kermit 8.0.200 Beta.02 (28 June 2001)
    • Major version number increased from 7 to 8.
    • SSH command.
    • More-consistent Kermit protocol defaults.
    • CONNECT idle timeout and action selection.
    • CONNECT status variable.
    • A way to allocate more space for filename lists.
    • Pseudoterminal handler fixed for late-model Linuxes.
    • Command-line option -dd for timestamped debug log.
    • Download directory now works for external protocols too.
    • GREP /COUNT:variable.
    • SET ATTRIBUTE RECORD-FORMAT { OFF, ON }.
    • Bug fixes.

    C-Kermit 8.0.200 Beta.03 (9 Sep 2001)

    C-Kermit 8.0.200 Beta.04 (16 Nov 2001)
    • New Unix man page
    • New Unix installation instructions
    • SET TELOPT policies are now enforced on non-Telnet ports if the server begins Telnet negotiations.
    • SET TERMINAL IDLE-ACTION { TELNET-NOP, TELNET-AYT }.
    • UUCP lockfile creation race condition fixed.
    • Dialout, modem signals, hangup, hardware flow control, etc, tested extensively on many platforms, numerous problems fixed.
    • Improved hints when dialing fails.
    • SET STOP-BITS 2 can now be given without SET FLOW HARDWARE.
    • Major improvements in RFC 2217 Telnet Com-Port Control.
    • Improved ability to REDIAL a modem server port.
    • kermit -h now shows the command name in the usage usage string.
    • kermit -h now shows ALL command-line options.
    • kermit -s blah, where blah is a symlink, now works.
    • --noperms command-line option = SET ATTRIBUTE PERMISSIONS OFF.
    • HTTP and HTTPS URLs now supported on the command line.
    • An http command-line personality is now available.
    • Initialization file streamlined to load faster, anachronisms removed.
    • Updated NEWS, INTRO, HELP text, SHOW commands. In particular, see SHOW COMM, HELP SET LINE, HELP WAIT.
    • Date/time arithmetic routines converted from floating-point to integer arithmetic (internally) for greater accuracy and portability.
    • Quoted strings containing commas no longer break macro execution.
    • Dynamic Kermit file-transfer timeouts are now much more aggressive.
    • New "hot keys" to turn debug.log on/off during file transfer.
    • Improved hints when file transfer fails.
    • FTP CD orientation messages are now printed.
    • -R now accepted on the FTP command line to request Recursion.
    • -m allows Active or Passive mode to be chosen on the FTP command line.
    • -dd on the FTP command line creates a timestamped debug.log.
    • FTP command-line security options filled in.
    • Improved automatic text/binary mode switching for MGET.
    • Removed spurious error messages that sometimes occur during MGET.
    • DIRECTORY, GREP, TYPE, HEAD, and TAIL now have a /OUTPUT:file option.
    • TYPE /NUMBER adds line numbers.
    • CAT = TYPE /NOPAGE; MORE = TYPE /PAGE.
    • GETOK ?-help fixed.
    • \v(timestamp) (= "\v(ndate) \v(time)")
    • \v(hour) (hour of the day, 0-23)
    • \funix2dospath() converts a UNIX path (/) to a DOS one (\).
    • \fdos2unixpath() converts a DOS (Windows, OS/2) path to a UNIX one.
    • \fkeywordval() parses name=value pair, allows macro keyword parameters.
    • We now make every attempt to not write passwords to the debug.log.
    • New Certificate Authority certificates file, includes the Kermit Project at Columbia University so you can access our IKSD securely.
    • Secure targets improved and better documented in Unix makefile.
    • All Linux (libc and glibc) builds consolidated under "make linux".
    • HP-UX makefile targets now have consistent names.
    • New aix50 and aix51 targets added.

    C-Kermit 8.0.200 Final (12 Dec 2001)
    • Remote/local-mode confusion on some platforms introduced in Beta.04, fixed.
    • Many of the makefile targets adjusted, new ones added.
    • New "make install" target should please most people.
    • New command: SHOW IKSD.
    • FTP over TLS.
    • Last-minute touchups to text messages, HELP text, etc.
    • Enable modem-signal reading for SCO OSR5 and Unixware 7.
    • Special superfast TRANSMIT /BINARY /NOECHO /NOWAIT mode added.
    • Fixed PBX dialing in unmarked-area-code case.
    • Improved SHOW COMMUNICATIONS tells lockfile directory, typical dialout device name.
    • Some FTP OPEN command parsing problems fixed.
    • Some errors in date arithmetic fixed.
    • New command: SET TERMINAL AUTODOWNLOAD { ..., ERROR { STOP, CONTINUE } }
    • New command: HELP FIREWALL.
    • SET MODEM HANGUP-METHOD DTR added as synonym for RS232-SIGNAL
    • Support for secure URL protocols added: telnets:, ftps:, https:.

    C-Kermit 8.0.201 (8 Feb 2002)

    C-Kermit 8.0.206 Beta.01 (11 Oct 2002)
    New commands:
    • ORIENTATION lists location-related variables and their values.
    • KCD changes to special directories by their symbolic names ("kcd ?" for a list).
    • SET CD HOME path to specify home directory for CD and KCD commands.
    • CONTINUE given at top level is equivalent to END -- handy when PROMPT'ed out of a script, to continue the script.

    New switches or operands for existing commands:
    • GETOK /TIMEOUT
    • ASK, ASKQ, GETOK /QUIET (suppresses error message on timeout)
    • COPY /APPEND now allows concatenating multiple source files into one dest file.
    • SET TCP { HTTP-PROXY, SOCKS-SERVER } /USER, /PASSWORD.
    • DIRECTORY command now accepts multiple filespecs, e.g. "dir a b c".

    SET QUIET ON now also applies to:
    • SET HOST connection progress messages.
    • "Press the X or E key to cancel" file-transfer message.
    • REMOTE CD response.
    • REMOTE LOGIN response.

    Improvements and new features:
    • Numerous FTP client fixes and new features, listed below.
    • C-Kermit, when in remote mode at the end of a file transfer, now prints a one-line "where" message. Control with SET TRANSFER REPORT.
    • Unix makefile "install" target now creates an UNINSTALL script.
    • Improved operation and performance on RFC 2217 Telnet connections.
    • Improved CONNECT (interactive terminal connection) performance.
    • HELP text updated for many commands.

    New or fixed makefile targets:
    • Solaris 9 (several variations)
    • Concurrent PowerMAX
    • Mac OS X 10.2
    • FreeBSD 1.0
    • FreeBSD 4.6, 5.0
    • AIX 5.2, 5.3

    Bugs fixed (general):
    • Failure to run in VMS Batch fixed.
    • LDIRECTORY fixed to run Kermit's built-in DIRECTORY command rather than an external one.
    • Fixed Solaris and other SVORPOSIX builds to find out their full hostnames rather than just the "uname -n" name.
    • Fixed some problems matching strings that start with ".".
    • Fixed some problems matching pattern that contain {a,b,c} lists.
    • Fixed erroneous reporting of text-mode reception as binary when sender did not report the file size (cosmetic only).
    • Many problems with SWITCH statements fixed.
    • Fixed SET OPTIONS DIRECTORY /DOTFILES to work for server too.
    • Fixed DELETE to print an error message if the file was not found.
    • Fixed SET CONTROL UNPREFIX ALL and SET PREFIXING NONE to do the same thing.
    • Fixed bugs executing macros from within the ON_EXIT macro.
    • \fday() and \fnday() fixed for dates prior to 17 Nov 1858.
    • Serial speed-changing bug in Linux fixed.
    • "Unbalanced braces" script parsing errors when using \{number} fixed.
    • "if defined \v(name)" fixed to behave as described in the book.
    • Fixed Problems caused by LOCAL variables whose names are left substrings of macro names.
    • The INPUT command was fixed to honor the PARITY setting.
    • Fixed bug with COPY to existing file that is longer than source file.
    • REINPUT command failed to strip braces/quotes around its target string.
    • Network directory lookups didn't work for SSH connections.
    • REMOTE SET { FILE, TRANSFER } CHARACTER-SET fixed.
    • Closed some holes whereby an incompletely received file was not deleted when SET FILE INCOMPLETE is DISCARD, e.g. when the Kermit is hung up upon.
    • SET XFER CHARACTER-SET TRANSPARENT fixed to do the same as SET XFER TRANSLATION OFF.
    • SET HOST PTY (e.g. SSH) connection fixed to pass along window-size changes.
    • C-Kermit search path for TAKE files was accidentally disabled.

    FTP client bugs fixed:
    • Character set translation was broken on little-endian (e.g. PC) architectures.
    • FTP PUT /SERVER-RENAME:, /RENAME-TO:, /MOVE-TO: switches were sticky.
    • Make SET TRANSFER MODE MANUAL apply to FTP.
    • Make SET FILE INCOMPLETE { KEEP, DISCARD } apply to FTP.
    • FTP MGET /UPDATE handled equal times incorrectly.
    • FTP MGET /RECOVER fixed to ignore file dates, use only size.
    • FTP MGET /RECOVER sometimes downloaded files it didn't need to.
    • FTP downloads with TRANSFER DISPLAY BRIEF could give misleading error messages.
    • FTP MGET temp file not deleted if FTP DEBUG set to OFF after it was ON.
    • LOCUS not switched back when FTP connection is lost.
    • Set incoming file date even if it was not completely received.
    • FTP MGET sent SIZE and MDTM commands even when it didn't have to.
    • FTP MGET sent SIZE and MDTM commands even when it knew they wouldn't work.
    • FTP MGET failed if no files were selected for download.
    • FTP MGET a* b* c* would fail to get any c*'s if no b*'s existed.
    • Big problems canceling MGET with Ctrl-C.
    • Some extraneous LOCUS dialogs squelched.
    • Some inconsistencies in SET FTP FILENAMES AUTO fixed.
    • Fixed file-descriptor pileup after multiple MGETs when using mkstemp().
    • Fixed "mget foo", where foo is a directory name.

    FTP improvements:
    • New FTP protocol features added (FEAT, MLSD).
    • FTP MGET /RECURSIVE now works as expected if server supports MLSD.
    • FTP MGET /DATES-DIFFER to download if local and remote file dates differ.
    • FTP DATES default changed to ON.
    • FTP MPUT, MGET /EXCEPT now allows up to 64 patterns (up from 8).
    • Top-level SITE and PASSIVE commands added for convenience.
    • MGET /COLLISION:APPEND /AS-NAME:newfile *.* puts all remote files into one local file.
    • SET FTP SERVER-TIME-OFFSET for when server has wrong timezone set.
    • Allow for alternative server interpretations of [M]MPUT /UNIQUE.
    • SET FTP ANONYMOUS-PASSWORD lets you specify the default anonymous password.
    • Allow "GET /RECURSIVE path/file" to force local subdirectory creation.
    • SET FTP DISPLAY is like SET TRANSFER DISPLAY but applies only to FTP.
    • FTP { ENABLE, DISABLE } new-protocol-feature-name.
    • FTP MGET /NODOTFILES.
    • Debug log now records FTP commands and responses in grep-able format.
  • [ Top ] [ Contents ] [ C-Kermit ] [ Kermit Home ]

    1. FIXES SINCE VERSION 7.0.196

    First, the changes from 7.0.196 to 7.0.197... Source and makefile tweaks to get successful builds on platforms that were not available in time for the 7.0 release:

    • 4.2BSD
    • 4.3BSD
    • AIX 4.3
    • AT&T 3B2 and 3B20
    • BeOS 4.5
    • CLIX
    • Interactive UNIX System V/386 R3.2 V4.1.1
    • OS-9/68000
    • OSF/1 1.3.
    • PS/2 AIX 1.2.1
    • SCO OSR5.0.x
    • SCO Xenix 2.3.4
    • SINIX 5.41/Intel
    • Stratus FTX
    • Stratus VOS
    • SunOS 4.1 with X.25
    • Ultrix 4.2
    • Unixware 2.0

    There were no functional changes from 196 to 197.

    Fixes applied after C-Kermit 7.0.197 was released:

    Source code: Big flexelint and "gcc -Wall" audit and cleanup.

    Configuration:

    • Solaris RTS/CTS (hardware flow control) didn't work.
    • BSDI RTS/CTS worked only in one direction.
    • FreeBSD 4.0 with ncurses 5.0 broke interactive command parsing.
    • QNX-32 build lacked -DBIGBUFOK so couldn't execute big macros.

    Connections:

    • SET HOST /PTY didn't work on some platforms.
    • Broken SET HOST /USER:xxx /PASSWORD:yyy /ACCOUNT:zzz switches fixed.
    • Transparent printing was broken in Unix.
    • ANSWER 0 (wait forever) didn't work.
    • Some problems in Multitech modem command strings.
    • Spurious "?Sorry, can't condition console terminal" errors.
    • Disabling modem command strings by setting them to nothing broke dialing.
    • SET DIAL TIMEOUT value was usually ignored.
    • SET DIAL METHOD PULSE didn't work.
    • Certain modem commands, if changed, not refreshed if modem type changed.
    • SET SESSION-LOG command was missing from VMS.
    • VMS session log format fixed for scripts.
    • HANGUP by dropping DTR didn't work in NetBSD.
    • SET FLOW /AUTO versus SET FLOW confusion fixed.
    • Spurious secondary Solaris lockfile removed.
    • SCO OSR5 DTR On/Off hangup.
    • UUCP lockfile race condition.

    Commands and scripts:

    • Missing CAUTIOUS and FAST commands restored.
    • Broken PTY command in late-model Linuxes fixed (API changed).
    • Fixed off-by-one error in command recall when switching direction.
    • Fixed recall of commands that contain '?'.
    • COPY /SWAP-BYTES didn't work on some architectures.
    • Various combinations of COPY switches didn't work.
    • Various problems with COPY or RENAME with a directory name as target.
    • SHIFT didn't decrement \v(argc) if used within IF, ELSE, or SWITCH block.
    • SHIFT didn't affect the \%* variable.
    • Divide by zero improperly handled in some \function()s.
    • Problems with RETURN from right-recursive functions.
    • FSEEK /LINE \%c LAST didn't work if already at end.
    • Some buffer vulnerabilities and potential memory leaks were discovered and fixed.
    • \frdirectory() fixed not to follow symbolic links.
    • SET EXIT WARNING OFF fixed to work when EXIT given in a script.
    • Missing DELETE and MKDIR error message fixed.
    • \fday() core dump for ancient dates fixed.

    File transfer:

    • SEND /COMMAND was broken.
    • CRECEIVE was broken (but RECEIVE /COMMAND was OK).
    • Quoting wildcard chars in filenames didn't work.
    • Problems canceling streaming file transfers with X or Z.
    • Problems shifting between streaming and windowing file transfer.
    • Non-FULL file-transfer displays erroneously said STREAMING when not.
    • An active SEND-LIST prevented GET from working.
    • SET SERVER GET-PATH interpretation of relative names like "." was wrong.
    • The MAIL command was broken.
    • "kermit -s *" might have skipped some files.
    • Transaction log entries were not made for external protocol transfers.
    • File count report fixed to show number of files actually transferred.
    • Fixed filename conversion to convert spaces to underscores.
    • Made SET PREFIXING / SET CONTROL PREFIX also adjust CLEARCHANNEL.
    • More "Receive window full" errors fixed.
    • Broken terminal buffering after curses display in Solaris fixed.
    • SET FILE INCOMPLETE DISCARD did not work in all cases.
    • Packet log changed to reformat the start-of-packet character printably.
    • Dynamic timeouts could grow ridiculously large.

    Character sets:

    • Hebrew-7 translations missed the letter Tav.
    • C1 area of CP1252 was ignored.
    • SET TRANSFER CHARACTER-SET TRANSPARENT could give garbage translations.
    • TRANSLATE might not work on Little Endian architectures.
    • Insufficient range checking in certain TRANSLATE operations.

    The following bugs in C-Kermit 8.0.200 were fixed in 8.0.201:

    Other fixes are listed in the previous section.

    [ Top ] [ Contents ] [ C-Kermit ] [ Kermit Home ]

    2. SSH AND HTTP

    2.1. SSH Connections

    This section does not apply to Kermit 95 2.0, which has its own built-in SSH client, which is documented SEPARATELY.
    On most UNIX platforms, C-Kermit can make SSH (Secure SHell) connection by running the external SSH command or program through its pseudoterminal interface. The command is:

    SSH text
    Tells Kermit to start the external SSH client, passing the given text to it on the command line. Normally the text is just the hostname, but it can be anything else that is acceptable to the ssh client. If the command succeeds, the connection is made and Kermit automatically enters CONNECT (terminal) mode. You can use the SSH command to make a connection to any host that has an SSH server.

    Kermit's SSH command gives you all the features of Kermit on an SSH connection: command language, file transfer, character-set translation, scripting, and all the rest. By default, C-Kermit invokes SSH with "-e none", which disables the ssh escape character and makes the connection transparent for purposes of file transfer. You can, however, change the SSH invocation to whatever else you might need (an explicit path, additional command-line arguments, etc) with:

    SET SSH COMMAND text
    Specifies the system command that Kermit's SSH command should use to invoke the external SSH client. Use this command to supply a specific path or alternative name, or to include different or more command-line options.

    In most cases, these connections work quite well. They can be scripted like any other connection, and file transfer goes as fast as, or faster than, on a regular Telnet connection. In some cases, however, the underlying pseudoterminal driver is a limiting factor, resulting in slow or failed file transfers. Sometimes you can work around such problems by reducing the Kermit packet length. Note that Kermit does not consider SSH connections to be reliable, so it does not offer to use streaming in Kermit protocol transfers (but you can force it with SET RELIABLE or SET STREAMING if you wish).

    The SSH command is like the TELNET command: it enters CONNECT mode automatically when the connection is made. Therefore, to script an SSH connection, use:

      set host /pty ssh -e none [ other-options ] host
      if fail ...
    
    to make the connection.

    Here's a sequence that can be used to make a connection to a given host using Telnet if the host accepts it, otherwise SSH:

      if not defined \%1 exit 1 Usage: \%0 host
      set quiet on
      set host \%1 23 /telnet
      if fail {
          set host /pty ssh -l \m(user) -e none \%1
          if fail exit 1 \%1: Telnet and SSH both fail
          echo SSH connection to \%1 successful  
      } else {
          echo Telnet connection to \%1 successful  
      }
    

    In SSH v2, it is possible to make an SSH connection direct to a Kermit server system if the host administrator has configured the SSH server to allow this; CLICK HERE for details.

    Since Kermit uses external ssh client software, and since there are different ssh clients (and different releases of each one), the exact command to be used to make an SSH/Kermit connection can vary. Here is the command for the OpenSSH 3.0.2p1 client:

    set host /pipe ssh -e none [ -l username ] -T -s hostname kermit
    

    Example:

    set host /pipe ssh -e none -l olga -T -s hq.xyzcorp.com kermit
    

    The SSH client might or might not prompt you for a password or other information before it makes the connection; this depends on your SSH configuration (your public and private keys, your authorized hosts file, etc). Here's a brief synopsis of the OpenSSH client command syntax ("man ssh" for details):

    -e none
    This tells the SSH client to use no escape character. Since we will be transferring files across the connection, we don't want the connection to suddenly block because some character in the data.

    -l username
    This is the username on the remote host. You can omit the -l option and its argument if your local and remote usernames are the same. If they are different, you must supply the remote username.

    -T
    This tells the SSH client to tell the SSH server not to allocate a pseudoterminal. We are not making a terminal connection, we don't need a terminal, and in fact if a terminal were allocated on the remote end, the connection would not work.

    -s ... kermit
    This tells the SSH client to tell the SSH server to start the specified subsystem ("kermit") once the connection is made. The subsystem name comes after the hostname.

    hostname
    The IP host name or address of the desired host.

    You might want to include other or additional ssh command-line options; "man ssh" explains what they are. Here are some examples for the OpenSSH 3.0.2p1 client:

    -oClearAllForwardings yes
    -oForwardAgent no
    -oForwardX11 no
    -oFallbackToRsh no
    These ensure that a secure connection is used and that the connection used for file transfer is not also used for forwarding other things that might be specified in the ssh_config file.

    -oProtocol 2
    (i.e. SSH v2) Ensures that the negotiated protocol supports subsystems.

    Once you have an SSH connection to a Kermit server, it's just like any other connection to a Kermit server (and very similar to a connection to an FTP server). You give the client file transfer and management commands for the server, and the server executes them. Of course you can also give the client any other commands you wish.

    [ SSH Kermit Server Subsystem ] [ Kermit 95 Built-in SSH Client ]

    2.2. HTTP Connections

    Hypertext Transfer Protocol, or HTTP, is the application protocol of the World Wide Web (WWW), used between Web browsers (clients) and Web servers. It allows a client to get files from websites, upload files to websites, delete files from websites, get information about website directories and files, and interact with server-side CGI scripts. C-Kermit includes an HTTP client capable of both clear-text and secure HTTP connections, that can do all these tasks and can be automated through the Kermit scripting language.

    Although C-Kermit 7.0 could make HTTP connections to Web servers, it could do so only when no other connection was open, and the procedure was somewhat awkward. C-Kermit 8.0 improves matters by:

    Persistent HTTP connections are managed with the following commands:

    HTTP [ switches ] OPEN [ security-options ] host-or-url [ port ]
    Opens a persistent connection to the specified host (IP host name or address) on the specified port. If any switches (options, listed in the next section) are included, their values are saved and used for all subsequent HTTP action commands on the same connection. If no port is specified, HTTP (80) is used. A Uniform Resource Locator (URL, RFC 1738) can be given instead of a hostname (or address) and port (but the URL can not include a directory/file path). The security options are explained below. The HTTP OPEN command replaces the C-Kermit 7.0 SET HOST hostname HTTP command, which no longer works with HTTP GET and related commands.

    HTTP CLOSE
    Closes any open HTTP connection and clears any saved switch values.

    A URL starts with a protocol name, which must be http or https in this case; optionally includes a username and password; and must contain a host name or address:

      protocol://[user[.password]]@host[:port][URI]
    

    HTTP is Hypertext Transfer Protocol. HTTPS is the secure (SSL/TLS) version of HTTP. The TCP service port is derived from the protocol prefix (so normally the ":port" field is omitted). Thus the URL protocol name specifies a default TCP service port and the URL user and password fields can take the place of the /USER and /PASSWORD switches (Section 2.2.1). The optional URI is a "compact string of characters for identifying an abstract or physical resource" (RFC 2396), such as a file. It must begin with a slash (/); if the URI is omitted, "/" is supplied. Examples:

    http open http://www.columbia.edu/
    Equivalent to http open www.columbia.edu or http open www.columbia.edu http.

    http open https://olga.secret@www1.xyzcorp.com/
    Equivalent to http /user:olga /pass:secret open www1.xyzcorp.com https.

    Persistence is accomplished unilaterally by C-Kermit 8.0. An HTTP 1.0 server closes the connection after each action. Although HTTP 1.1 allows multiple actions on the same connection, an HTTP 1.1 server tends to close the connection if it is idle for more than a few seconds, to defend itself against denial-of-service attacks. But when you use Kermit's HTTP OPEN command to create a connection, Kermit reopens it automatically (if necessary) for each HTTP action until you close it with HTTP CLOSE, regardless of the server's HTTP protocol version, or how many times it closes the connection.

    Firewalls can be negotiated through proxies with the following commands:

    SET TCP HTTP-PROXY [ host[:port] ]
    If a host (by hostname or IP address) is specified, Kermit uses it as a proxy server when attempting outgoing TCP connections -- not only HTTP connections, but all TCP/IP connections, Telnet and FTP included. This allows Kermit to adapt to the HTTP firewall penetration method (as opposed to other methods such as SOCKS4). If no hostname or ip-address is specified, any previously specified Proxy server is removed. If no port number is specified, the "http" service is used. This command must be given before the HTTP OPEN command if a proxy is to be used or canceled.

    HTTP [ switches ] CONNECT host[:port]
    Instructs the HTTP server to act as a proxy, establishing a connection to the specified host (IP hostname or address) on the given port (80 = HTTP by default) and to redirect all data transmitted between Kermit and itself to the given host for the life of the connection. This command is to be used only for debugging HTTP proxy connections. If a proxy connection is required, instruct Kermit to use the proxy with the SET TCP HTTP-PROXY command.

    2.2.1. HTTP Command Switches

    HTTP switches, like all other switches, are optional. When HTTP switches are included with the HTTP OPEN command, they apply automatically to this and all subsequent HTTP actions (GET, PUT, ...) on the same connection until an HTTP CLOSE command is given. So if you include switches (or the equivalent URL fields, such as user and password) in the HTTP OPEN command, you can omit them from subsequent commands on the same connection. If the connection has closed since your last command, it is automatically reopened with the same options.

    If you include switches with an HTTP action command (such as GET or PUT), they apply only to that command.

    /USER:name
    To be used in case a page requires a username for access. The username is sent with page requests. If it is given with the OPEN command it is saved until needed. If a username is included in a URL, it overrides the username given in the switch. CAUTION: Username and password (and all other information, including credit card numbers and other material that you might prefer to protect from public view) are sent across the network in clear text on regular HTTP connections, but authentication is performed securely on HTTPS connections.

    /PASSWORD:text
    To be used in case a web page requires a password for access. The password is sent with page requests. If it is given with the OPEN command it is saved until needed. If a password is given in a URL, it overrides the one given here. CAUTION: (same as for /USER:).

    /AGENT:user-agent
    Identifies the client to the server. Overrides the default agent string, which is "C-Kermit" (for C-Kermit) or "Kermit-95" (for Kermit 95).

    /ARRAY:array-designator
    Tells Kermit to store the response headers in the given array, one line per element. The array need not be declared in advance. Example: /array:&a.

    /TOSCREEN
    Tells Kermit to display any response text on the screen. It applies independently of the output file specification; thus it is possible to have the server response go to the screen, a file, both, or neither.

    /HEADER:header-item(s)
    Used for specifying any optional headers to be sent with HTTP requests.

      /HEADER:tag:value
    

    To send more than one header, use braces for grouping:

      /HEADER:{{tag:value}{tag:value}...}
    

    For a list of valid tags and value formats see RFC 2616, "Hypertext Transfer Protocol -- HTTP/1.1". A maximum of eight headers may be specified.

    2.2.2. HTTP Action Commands

    HTTP actions can occur within a persistent connection, or they can be self-contained ("connectionless"). A persistent HTTP connection begins with an HTTP OPEN command, followed by zero or more HTTP action commands, and is terminated with an HTTP CLOSE command:

      http open www.columbia.edu
      if failure stop 1 HTTP OPEN failed: \v(http_message)
      http get kermit/index.html
      if failure stop 1 HTTP GET failed: \v(http_message)
      (more actions possible here...)
      http close
    

    A self-contained HTTP action occurs when a URL is given instead of a remote file name to an HTTP action command. In this case, Kermit makes the HTTP connection, takes the action, and then closes the connection. If an HTTP connection was already open, it is closed silently and automatically.

      http get http://www.kermitproject.org/index.html
    

    Kermit's HTTP action commands are as follows. Switches may be included with any of these to override switch (or default) values given in the HTTP OPEN command.

    HTTP [ switches ] GET remote-filename [ local-filename ]
    Retrieves the named file from the server specified in the most recent HTTP OPEN command for which a corresponding HTTP CLOSE command has not been given. The filename may not include wildcards (HTTP protocol does not support them). If no HTTP OPEN command is in effect, this form of the HTTP GET command fails. The default local filename is the same as the remote name, but with any pathname stripped. For example, the command http get kermit/index.html stores the file in the current local directory as index.html. If the /HEADERS: switch is included, information about the file is also stored in the specified array (explained in Section 2.2.3). All files are transferred in binary mode. HTTP does not provide for record-format or character-set conversion.

    HTTP [ switches ] GET url [ local-filename ]
    When HTTP GET is given a URL rather than a filename, Kermit opens a connection to the designated server (closing any previously open HTTP connection), gets the file, and then closes the connection. If the URL does not include a filename, index.html is supplied. This is the self-contained one-step "connectionless" method for getting a file from a Web server. The data is not interpreted; HTTP GET is like "lynx -source" rather than "lynx -dump".

    In the remaining HTTP action commands, the distinction between a remote filename and a URL are the same as in the HTTP GET command.

    HTTP [ switches ] HEAD remote-filename-or-url [ local-filename ]
    Like GET except without actually getting the file; instead it retrieves only the headers. If the /ARRAY: or /TOSCREEN switch is included, there is no default local output filename but you can still specify one. If neither of these switches is included, the default local filename is the same as the remote filename, but with any path stripped and with ".head" appended. The HEAD command can be used in a script with the /ARRAY: switch to retrieve information about the requested resource to determine whether the resource should actually be retrieved with a subsequent GET request.

    HTTP [ switches ] INDEX remote-directory-or-url [ local-filename ]
    Asks the server to send a listing of the files in the given server directory. This command is not supported by most Web servers. Even when it is supported, there is no standard format for the listing.

    HTTP [ switches ] POST [ /MIME-TYPE:type ] source-file remote-path-or-url [ result-file ]
    Sends data to a process running on the remote host; the result is usually an HTML file but could be anything. The data to be posted must be read from a local file (the source-file). If a result file is specified, Kermit stores the server's response in it.

    HTTP [ switches ] PUT [ MIME-TYPE:type ] local-file [ remote-file-or-url [ result-file ] ]
    Uploads a local file to the server. Only the name of a single file can be given; wildcards (and group transfers) are not supported by HTTP protocol. If no remote filename is given, the file is sent with the same name as the local file, but with any pathname stripped.

    HTTP [ switches ] DELETE remote-file-or-url [ local-result-file ]
    Asks the server to delete the specified single file. If a result file is specified, it will contain any response data returned by the server.

    Note the limitations of HTTP protocol compared to (say) FTP or Kermit. There is no command for changing directories, no standard way to get file or directory lists, no way to transfer file groups by using wildcard notation, etc, and therefore no good way to (say) fetch all pages, descend through subdirectories, perform automatic updates, etc. There is no assurance a connection will stay open and, as noted, there is no provision for data conversion between unlike platforms. The data's MIME headers can be used for postprocessing.

    2.2.3. HTTP Headers

    Each HTTP request and response contains a set of name/value pairs called headers. HTTP headers are specified in RFC 2616. For example, an HTTP GET request for /index.html on www.columbia.edu contains the following headers:

      GET /index.html HTTP/1.1
      Host: www.columbia.edu:80
      User-agent: C-Kermit 8.0
      Authorization: Basic base64-encoded-username-password
    

    These might be followed by any others specified with a /HEADERS: switch:

      Accept: image/gif, image/x-xbitmap, image/jpeg, *.*
      Accept-Encoding: gzip
      Accept-Language: en
      Accept-Charset: iso-8859-1,utf-8
      Cookie: cookie-data
    

    The server sends back a short report about the file prior to sending the file contents. Example:

      HTTP/1.1 200 OK
      Date: Fri, 24 Aug 2001 21:09:39 GMT
      Server: Apache/1.3.4 (Unix)
      Last-Modified: Mon, 06 Aug 2001 21:16:13 GMT
      ETag: "1fa137-10d7-3b6f091d"
      Accept-Ranges: bytes
      Content-Length: 4311
      Content-Type: text/html
    

    If you want to have this information available to a Kermit script you can use the /ARRAY switch to have Kermit put it in array, one line per array element. Example:

      set exit warning off
      http open www.columbia.edu
      if fail exit 1 Can't reach server
      http /array:&a get /index.html
      if fail exit 1 Can't get file
      echo Header lines: \fdim(&a)
      for \%i 1 \fdim(&a) 1 {
          echo \%i. \&a[\%i]
      }
    

    Note that the "Date:" item is the current date and time; the "Last-Modified:" item is the file's modification date and time. An example showing how to use this information is presented in Section 8.13.7.

    2.2.4. Secure HTTP Connections

    SSL/TLS (Secure Sockets Layer / Transport Layer Security) is the protocol used to secure HTTP, SMTP, and other Internet applications. See the C-Kermit Reference Section 5.4 for an introduction to SSL/TLS. To make a secure HTTP connection, you need:

    1. A secure client (a version of C-Kermit or Kermit 95 with SSL/TLS security built in). Type "check ssl" at the Kermit prompt to make sure you have it.
    2. A secure server to connect to.
    3. The CA Root Certificate used to authenticate the server to the client. (see Section 15 of the security reference for an introduction to certificates).

    And you must make a connection to the secure HTTP port: service name HTTPS, port number 443 (as opposed to service HTTP, port 80). You can also make secure connections to other ports by including the /TLS or /SSL switch with the HTTP OPEN command, if the host supports SSL/TLS on the given port:

    The quality of the SSL/TLS connection depends on the cipher suite. There are several possibilities:

    Anonymous cipher suite:
    If an anonymous cipher suite is negotiated, the connection is encrypted but there is no authentication. This connection is subject to a Man-In-The-Middle (MITM) attack.

    X.509 certificate on the server:
    When you connect to certain secure servers, an X.509 certificate is returned. This certificate is issued to a special hostname, something like www1.xyzcorp.com or wwws.xyzcorp.com (rather than the normal www.xyzcorp.com). It is signed by the host's Certificate Authority (CA). If the host certificate is configured on the client, it can be used to verify the certificate received from the server. If the certificate it verified as authentic, a check is made to ensure it has not expired and it was issued to the host you were attempting to connect to. If you had asked to connect to (say) www.xyzcorp.com but were given a certificate for www1.xyzcorp.com, you would be prompted for permission to continue.

    If the verification succeeded, the connection would be encrypted with one-way (server-to-client) authentication. This connection is not subject to a MITM attack.

    If a username and password are transmitted over this connection, they are not subject to interception. However, the standard risks associated with passing the password to the host for verification apply; for example, if the host has been compromised, the password will be compromised.

    X.509 client certificate:
    If a connection has been established with an X.509 server certificate, the server can ask the client to send a certificate of its own. This certificate must be verified against a CA Root certificate. The certificate itself (or subject info from the certificate) is used to determine the authorization for the client, and if successful, the username and password need not be sent to the server.

    Kerberos 5:
    Instead of using X.509 certificates, Kerberos 5 can be used to perform the authentication and key exchange. In this situation, there is mutual authentication between the client and server. The Kerberos 5 principal is used by the server to look up the appropriate authorization data. There is no need to send username and password.

    An HTTP connection is made with the HTTP OPEN command:

    HTTP [ switches ] OPEN [ { /SSL, /TLS } ] host [ port ]
    If /SSL or /TLS switches are included (these are synonyms), or if the service is HTTPS or the port is 443, a secure connection is attempted using the current authentication settings; see HELP SET AUTHENTICATION for details (Section 6.2 of the security reference). If the no /SSL or /TLS switch is included but the port is 443 or the service is HTTPS, a secure connection is attempted. If an /SSL or /TLS switch is included but a port is not specified, an SSL/TLS connection is attempted on the default port (80).

    Certificates are covered in the separate Kermit Security Reference for C-Kermit 8.0. You should let Kermit know to verify certificates with the SET AUTHENTICATION TLS command. For example:

    SET AUTHENTICATION TLS CRL-DIR directory
    Specifies a directory that contains certificate revocation files where each file is named by the hash of the certificate that has been revoked.

    SET AUTHENTICATION TLS CRL-FILE filename
    Specifies a file that contains a list of certificate revocations.

    SET AUTHENTICATION TLS VERIFY-DIR directory
    Specifies a directory that contains root CA certificate files used to verify the certificate chains presented by the peer. Each file is named by a hash of the certificate.

    SET AUTHENTICATION TLS VERIFY-FILE filename
    Specifies a file that contains root CA certificates to be used for verifying certificate chains.

    SET AUTHENTICATION TLS VERIFY OFF
    Tells Kermit not to require a certificate and accept any certificate that is presented regardless of whether it is valid.

    There are many other options; see the security document for details.

    Now suppose you need need to fetch the file denoted by the following URL:

      https://myuserid:mypassword@wwws.xyzcorp.com/clients/info/secret.html
    

    Once you have set up the handling of certificates as desired, you can use the following Kermit commands:

      http /user:myuserid /password:mypassword open www1.xyzcorp.com https
      if success {
          http get /clients/info/secret.html
          http close
      }
    
    As another example, let's say that you have a web form you need to populate with three fields: red,white and blue.

      <FORM ACTION="http://www.xyzcorp.com/cgi-bin/form.cgi" METHOD="POST">
      <INPUT NAME="Red">
      <INPUT NAME="White">
      <INPUT NAME="Blue">
      </FORM>
    

    You can handle this with the HTTP POST command. The data to be posted is stored in the local file data.txt.

      Red=seven stripes&White=six stripes&Blue=fifty stars
    

    and the response from the server will be stored into response.txt.

      http open www.xyzcorp.com http
      if success {
        http /array:c post data.txt /cgi-bin/form.cgi response.txt
        http close
      }
    
    In this scenario, the Common Gateway Interface (CGI) sends a response whether it succeeds or fails in a script-dependent manner. The script can either report success and enclose the response data; or it might send a 302 Found error which indicates that the "Location:" header should be used to determine the URL at which the data can be found.

    2.2.5. HTTP Variables

    \v(http_code)
    The HTTP protocol code number of the most recent server reply, e.g. 404 for "not found".

    \v(http_connected)
    1 when an HTTP connection is open, 0 when there is no HTTP connection.

    \v(http_host)
    If an HTTP connection is open, the hostname:port, e.g. www.columbia.edu:80; otherwise, empty.

    \v(http_message)
    Server error message, if any, from most recent HTTP command.

    \v(http_security)
    A list of the security parameters and values for the current connection, if any. Empty if the connection is not to a secure server, or there is no connection.

    To display all the HTTP variables at once, type SHOW VAR HTTP:

      C-Kermit> http open www.columbia.edu
      C-Kermit> http get lkjlkjlkjlkj 
      C-Kermit> sho var http
       \v(http_code) = 404
       \v(http_connected) = 1
       \v(http_host) = www.columbia.edu:80
       \v(http_message) = Not Found
       \v(http_security) = NULL
      C-Kermit>
    

    2.2.6. The HTTP Command-Line Personality

    If you invoke C-Kermit with the name "http" or "https", you can use a special set of HTTP-specific command-line options. You can do this by creating a symbolic linke "http" or "https" to the C-Kermit 8.0 executable, or by having a separate copy of it called "http" or "https". Here's the usage message ("http -h"):

      Usage: ./http host [ options... ]
       -h             This message.
       -d             Debug to debug.log.
       -S             Stay (issue command prompt when done).
       -Y             Do not execute Kermit initialization file.
       -q             Quiet (suppress most messages).
       -u name        Username.
       -P password    Password.
       -g pathname    Get remote pathname.
       -p pathname    Put remote pathname.
       -H pathname    Head remote pathname.
       -l pathname    Local path for -g, -p, and -H.
       -z opt[=value] Security options...
          cert=file   Client certificate file
          certsok     Accept all certificates
          key=file    Client private key file
          secure      Use SSL
          verify=n    0 = none, 1 = peer , 2 = certificate required
    

    The "host" argument is the name of a Web host, e.g. www.columbia.edu. The action options are -p, -g, and -H. If you give an action option, Kermit does the action and then exits. If you give a host without an action option, Kermit makes an HTTP connection to the host and then gives you the C-Kermit prompt. Here's a simple example that fetches a publicly readable Web page:

      http www.columbia.edu -g kermit/index.html
    

    If you need to access a website for which a username and password are required, you can supply them on the command line with -u and -P. If you include a username but omit the password, Kermit prompts you for it:

      http www.columbia.edu -u olga -p kermit/index.html -l index.html
      Password:
    

    Note that when PUT'ing files to websites, you have to supply both the -p (remote pathname) and -l (local path) options.

    If your version of Kermit is built with SSL/TLS security, you can also use the -z option to make secure HTTP (https) connections.

    Finally, as noted in Section 16, you can also give a URL instead of a host name and options.

    [ Top ] [ Contents ] [ C-Kermit Home ] [ Kermit Home ]

    3. KERMIT'S BUILT-IN FTP CLIENT

    3.1.  Making and Managing FTP Connections
    3.2.  Making Secure FTP Connections
    3.3.  Setting FTP Preferences
    3.4.  Managing Directories and Files
    3.5.  Uploading Files With FTP
    3.6.  Downloading Files With FTP
    3.7.  Translating Character Sets
    3.8.  FTP Command Shortcuts
    3.9.  Dual Sessions
    3.10. Automating FTP Sessions
    3.11. Advanced FTP Protocol Features

    Earlier versions of C-Kermit and K95 included an FTP command, but it simply invoked an external FTP client. Now, by popular demand, Kermit includes its own built-in FTP client that offers the following advantages over traditional FTP clients (and its previous interface to them):

    And best of all:

    [ Top ] [ FTP Top ] [ FTP Client Overview ] [ FTP Script Tutorial ] [ C-Kermit Home ] [ Kermit Home ]

    3.1. Making and Managing FTP Connections

    Each copy of Kermit can have one FTP connection open at a time. FTP connections are independent of regular terminal connections; a terminal connection (serial or network via SET LINE, DIAL, SET HOST, TELNET, etc) may be, but need not be, open at the same time as an FTP connection, and terminal connections can also be closed, and new connections opened, without interfering with the FTP connection (and vice versa). Thus, for example, Kermit can have an FTP connection and a TELNET connection open to the same host simultaneously, using the TELNET connection (e.g.) to send mail or take other desired actions as various FTP actions complete. Of course, each copy of Kermit can do only one thing at a time, so it can't (for example) transfer a file with FTP and another file with Kermit protocol simultaneously.

    A Kermit FTP session can be established by command-line options, by URL, or by interactive commands.

    3.1.1. Kermit Command-Line Options for FTP

    The new command-line option '-9' (sorry, we're out of letters) can be used when starting C-Kermit, telling it to make an FTP connection:

      kermit -9 hostname
    

    or if a non-default FTP port is needed:

      kermit -9 hostname:port
    

    You can also specify the username on the command line with the -M ("My User ID") option that was already there for other connection types:

      kermit -9 hostname -M olga
    

    If you specify the username on the command line, Kermit uses it when making the connection and does not prompt you for it (but it does prompt you for the password if one is required).

    Once the connection is made, you get the regular Kermit prompt, and can give interactive commands such as the ones described below. When you give a BYE command, Kermit closes the session and exits, just as a regular FTP client would do. If you don't want Kermit to exit when you give a BYE command, include the -S ("Stay") option on the command line.

    Other Kermit command-line options that are not specific to non-FTP connections should affect the FTP session in the expected ways; for example, -i and -T force binary and text mode transfers, respectively.

    File transfers can not be initiated on the "kermit -9" command line; for that you need to use Kermit's FTP personality (next section) or you can use URLs (Section 3.1.3).

    3.1.2. The FTP Command-Line Personality

    If you want to replace your regular FTP client with C-Kermit, you can make a link called "ftp" to the C-Kermit binary (or you can store a copy of the C-Kermit binary under the name "ftp"). When C-Kermit is invoked with a program name of "ftp" (or "FTP", case doesn't matter), it assumes the command-line personality of the regular FTP client:

      ftp [ options ] hostname [ port ]
    

    In this case the options are like those of a regular FTP client:

      -d  Debug: enables debug messages and creates a debug.log file.
      -n  No autologin: Kermit should not send your user ID automatically.
      -t  Packet trace: accepted but is treated the same as -d.
      -v  Verbose: accepted but ignored (operation is verbose by default).
      -i  Not interactive: accepted but ignored.
    

    and the hostname can also be a URL (explained in Section 3.1.3). To specify a non-default TCP port for the FTP server, include the port number or name after the hostname.

    There are also some bonus options that allow you to execute an entire FTP session from the shell command line, as long as you don't include the -n option. These are not available with regular FTP clients, and at least one of these options (-g) conflicts with UNIX ftp (where -g means "no globbing", which does not apply to Kermit), and some of them (like the options above) also conflict with regular Kermit command-line options:

      -m mode      = "passive" (default) or "active"
      -Y            Don't execute the Kermit initialization file [1]
      -q            Quiet, suppresses all but error messages [1]
      -S            Stay, don't exit automatically [1]
      -A            Autologin anonymously [2]
      -u name       Username for autologin [2] (synonym: -M [1])
      -P password   Password for autologin (see cautions below) [2]
      -D directory  cd after autologin [2]
      -b            Binary mode [2]
      -a            Text ("ascii") mode [2] (synonym: -T [1])
      -R            Recursive (works with -p) [4]
      -p files      Files to put (upload) after autologin [2] (synonym: -s [1])
      -g files      Files to get (download) after autologin [3]
    

    [1] Same as Kermit, not available in regular FTP clients.
    [2] Conflicts with Kermit, not available in regular FTP clients.
    [3] Same as Kermit, conflicts with regular FTP clients.
    [4] Conflicts with Kermit, available in some FTP clients.

    Fancier options such as restart, character-set translation, filename collision selection, automatic move/rename/delete, etc, are not available from the command line; for these you can use the commands described in the following sections. The -R option might also work with -g (GET) but that depends on the server.

    The following security options are also available, explained in Section 3.2:

      -k realm      Kerberos 4 realm [4]
      -f            Kerberos 5 credentials forwarding [4]
      -x            autoencryption mode [4]
      -c cipher     SRP cipher type [4]
      -H hash       SRP encryption hash [4]
      -z option     Security options [4]
    

    If you include -A or specify a name of "anonymous" or "ftp", you are logged in anonymously and, in the absence of -P, Kermit automatically supplies a password of "user@host", where "user" is your local user ID, and "host" is the hostname of the computer where Kermit is running. If you do not include -p or -g, Kermit enters command mode so you can type commands or execute them from a script.

    If you include -p or -g, Kermit attempts to transfer the specified files and then exits automatically at the end of the transfer unless you also included -S (Stay). It uses the "brief" file transfer display (one line per file) unless you include the -q option to suppress it.

    When uploading files with -p, Kermit switches automatically between text and binary mode for each file.

    When downloading, you can either specify a particular mode (text or binary) to be used for all the files, or you can let Kermit select the type for each file automatically, based on its name (see Sections 3.5 and 3.6 for greater detail). In UNIX be sure to quote any wildcard characters to prevent the shell from expanding them, as shown in the examples just below. Filename collisions are handled according Kermit's FILE COLLISION setting (if specified in your Kermit customization file; otherwise the default, which is BACKUP).

    It should go without saying that the -P option should be used with caution. In addition to the well-known risks of transmitting plaintext passwords over the Internet, in this case the password also echos to the screen if you type it, and can be seen in ps and w listings that show the user's currently active command and command-line arguments. Thus command-line FTP sessions are most appropriate for secure or anonymous connections (those that do not require passwords).

    Here's an example in which you download the latest C-Kermit "tarball" from the Kermit Project FTP archive:

      ftp -A ftp.kermitproject.edu -bg kermit/archives/ckermit.tar.gz
    

    This assumes that "ftp" is a symbolic link to C-Kermit. It logs you in anonymously and gets the ckermit.tar.gz file in binary mode from the kermit/archives directory.

    Here's a slightly more ambitious example that illustrates CD'ing to the desired server directory to get a group of files in text mode (in this case the C-Kermit source files):

      ftp -A ftp.kermitproject.org -D kermit/f -ag "ck[cuw]*.[cwh]" makefile
    

    In this case we CD to the kermit/f directory so we don't have to include it in each file specification, and we quote the ck[cuw]*.[cwh] specification so the shell doesn't expand it, since we have to pass it as-is to the server. Note also that the quotes don't go around the entire file list; only around each file specification that needs to be quoted.

    Here's one more example, that uploads a debug log file in binary mode to the Kermit incoming directory (as we might ask you to do when following up on a problem report):

      ftp -A ftp.kermitproject.org -D kermit/incoming -bp debug.log
    

    In this case the -D option is required to tell the server where to put the incoming file.

    Unless the -Y option is included, your Kermit initialization file (.mykermrc in UNIX, K95.INI in Windows) is executed before the command line options, so you can set any FTP-related preferences there, as described in the subsequent sections.

    3.1.3. The FTP URL Interpreter

    If Kermit is invoked with either its regular personality (as "kermit") or its FTP personality (as "ftp"), you can also give a URL (Universal Resource Locator) instead of a hostname and options, with or without a username and password:
    ftp ftp://user:password@host/path
    ftp ftp://user@host/path
    ftp ftp://@host/path   (or ftp://:@host/path)
    ftp ftp://host/path
    kermit ftp://host/path

    If the FTP personality is used, the service must be "ftp". In all cases, a hostname or address must be included. If a user is included but no password, you are prompted for the password. If a path (filename) is included:

    If no path (and no action options) are included, an interactive FTP session is started, as in this example:
    ftp ftp://ftp.kermitproject.org

    If a path is included, but a username is not included, "anonymous" is used and an appropriate user@host password is supplied automatically. If authentication is successful, Kermit attempts to GET the file indicated by the path or, if the path is the name of a directory, it asks the server for a directory listing. In both cases, Kermit disconnects from the server and exits after the operation is complete (unless you have included the -S option on the command line).

    Here's an example that gets a listing of the Kermit directory at the Kermit ftp site:
    ftp ftp://ftp.kermitproject.org/kermit/

    This example gets the top-level READ.ME file from the same directory:
    ftp ftp://ftp.kermitproject.org/kermit/READ.ME

    Here's the same example, but requesting a text-mode transfer:
    ftp -T ftp://ftp.kermitproject.org/kermit/READ.ME
    This illustrates that you can mix command-line options and URLs if you desire.

    Here's an example that logs in as a (fictitious) real user to get a file:
    ftp ftp://olga@ftp.xyzcorp.com/resume.txt
    The password is not included, so Kermit prompts for it.

    This scheme allows Kermit to be used as the FTP helper of other applications, such as Web browsers, with all its advantages over other FTP clients (especially the ones that are built in to most Web browsers), e.g. that it can be given wildcards, and it can pick text and binary mode automatically for each file.

    HINT: suppose somebody sends you an FTP URL in email, or you see it in some text. If your terminal screen supports copy/paste, copy the url, and then at the shell prompt type "kermit", a space, and then paste the URL, e.g.:

      $ kermit ftp://alpha.greenie.net/pub/mgetty/source/1.1/mgetty1.1.27-O
    

    "$ is the shell prompt; the part you type is underlined, the rest is pasted in. Kermit does the rest.

    3.1.4. Interactive FTP Session Establishment

    As you read this and the following sections, bear in mind that any command that can be given at the prompt can also be used in a script program. Kermit's script programming language is the same as its interactive command language. CLICK HERE if you would like to learn a bit more about script writing.

    An FTP session is established with the FTP OPEN command:

    FTP [ OPEN ] [ { /SSL, /TLS } ] hostname [ switches ] [ port ]
    Opens an FTP connection to the given host on the given port and, if FTP AUTOLOGIN is ON, also logs you in to the server, prompting for username and password if necessary. If no port is specified, the regular FTP protocol port (21) is used. The OPEN keyword is optional (unless the hostname conflicts with one of the FTP command keywords, which you can list by typing "ftp ?").

    The hostname can be an IP host name, numeric IP address, or if you have a network directory active (SET NETWORK DIRECTORY; see Chapter 6 of Using C-Kermit), an entry name in the directory. In the latter case, if the given hostname matches exactly one entry, the associated name or address is used; if it matches more than one, Kermit cycles through them until one is found that can be opened; if it matches none, then the hostname is used as-is. If a directory is active but you want to bypass directory lookup, include an "=" sign at the beginning of the hostname, and/or use a numeric IP address.

    When an FTP connection is opened, the default file-transfer mode is set to binary if the client and server platforms are alike (e.g. both of them are some kind of UNIX), and to text ("ascii") if they are not alike. This has no particular effect for uploading since Kermit automatically switches between text and binary mode for each file, but might be important for downloading. The connection is also set to Stream mode and File structure. Record- or page-oriented file transfers are not supported by C-Kermit's FTP client.

    The optional FTP OPEN switches are:

    /ANONYMOUS
    Logs you in anonymously, automatically supplying username "anonymous" and user@host as the password, based on your local user and host names.

    /NOLOGIN
    Overrides SET FTP AUTOLOGIN ON for this connection only.

    /USER:name
    Uses the given username to log you in, thus avoiding the Name: prompt.
    Overrides SET FTP AUTOLOGIN OFF for this connection only.

    /PASSWORD:text
    Uses the given text as your password, thus avoiding the Password: prompt. This switch is not recommended for use in script files, which would be a security risk.

    /ACCOUNT:text
    Uses the given text as your account (or secondary password, depending on the requirements of the server; most servers do not require or accept an account name). If an account is not supplied, you are not prompted for one.

    /PASSIVE
    Opens the connection in passive mode. Passive mode is the default in Kermit's FTP client, unlike in most others, since it works better through firewalls. The /PASSIVE and /ACTIVE switches apply only to the connection that is being opened, and do not affect the global FTP PASSIVE-MODE setting.

    /ACTIVE
    Opens the connection in active mode. Use this switch if the server does not support passive mode, or use the command SET FTP PASSIVE-MODE OFF.

    /NOINIT
    Added in C-Kermit 8.0.201.   Tells C-Kermit not to send REST, STRU, FEAT, and MODE commands to the server when the connection is opened, since these have been reported to cause confusion in certain servers.

    When a username or password is missing, a prompt is issued at the controlling terminal and you must type the response; the response can not be scripted. Use the switches to avoid prompts, or one of the secure authentication methods described in the next section, or see SET FTP AUTOLOGIN and the FTP USER and similar commands described later in this section.

    Examples:

      ftp open ftp.kermitproject.org /anonymous  ; Open and log in anonymously
      ftp ftp.kermitproject.org /anonymous       ; The OPEN keyword can be omitted
      ftp xyzcorp.com                          ; Open and maybe prompt for username
      ftp xyzcorp.com /user:olga               ; Open and log in as olga
      ftp testing.abccorp.com 449              ; Specify a special TCP port number
      ftp testing.abccorp.com /user:olaf /password:secret 449
    

    The FTP OPEN command succeeds if a connection was opened to the server (even if the given username and password were not valid) and fails otherwise (see Section 3.8 for details).

    When your FTP session is complete, you can terminate it as follows:

    FTP BYE
    Closes the FTP connection if one was open. The FTP prefix can be omitted if no other connection is open at the same time (see Section 3.8 for details). If a connection log is active, an FTP record is written to it. If Kermit was started with the -9 command-line option or with its FTP command-line personality, and the -S (Stay) option was not given, AND there is no other active connection, the FTP BYE command also exits, just as it does on a regular FTP client. Synonyms: FTP CLOSE, FTP QUIT (but if the FTP prefix is omitted from QUIT, this becomes the regular Kermit QUIT command, which is equivalent to EXIT; i.e. it closes the connection and exits from Kermit).

    The following commands can be used to achieve greater control over the connection and login process:

    SET FTP ANONYMOUS-PASSWORD text
    Allows you to choose the password text to be sent automatically by Kermit when you open an FTP connection with the /ANONYMOUS switch.

    SET FTP AUTOLOGIN { ON, OFF }
    If you give this command prior to opening an FTP connection, it controls whether Kermit tries to log you in automatically as part of the connection process. Normally ON, which means the username and password are sent automatically (and prompted for if they are not yet known). When OFF, FTP OPEN connects to the server without logging in. OFF is equivalent to the -n command-line option when using Kermit's FTP command-line personality.

    FTP USER name [ password [ account ] ]
    Used to log in to an FTP server to which a connection has been made without autologin, or when autologin failed. If the password is furnished on the command line, it is used; otherwise you are prompted for a password. An account may also be furnished if required by the server; it is not required by Kermit and is not prompted for if omitted. Synonyms: USER, FTP LOGIN.

    FTP ACCOUNT text
    Sends an account name to a server that supports accounts. If the server does not support accounts, an error response occurs. If the server does support accounts, the account is accepted if it is valid and rejected if it is not. The account might be used for charging purposes or it might be a secondary password, or it might be used for any other purpose, such as an access password for a particular disk. Servers that support accounts might or might not allow or require the account to be sent prior to login; usually it is sent after login, if at all. Synonym: ACCOUNT.

    Example:

    set ftp autologin off                  ; One thing at a time please
    ftp xyzcorp.com                        ; Try to make the connection
    if fail exit 1 FTP connection failed   ; Check that it was made
    ftp user olga secret                   ; Now log in to the server
    if fail exit 1 FTP login failed        ; Check that it worked
    ftp account 103896854                  ; Login OK - send account
    if fail echo WARNING - FTP ACCT failed ; Warn if problem
    ...                                    ; (have session here)
    bye                                    ; Log out and disconnect
    

    The following commands are used to control or get information about the FTP connection. Any particular FTP server does not necessarily support all of them.

    FTP RESET
    Terminates a user session but leaves the connection open, allowing a new login via FTP USER.

    FTP IDLE [ number ]
    Most FTP servers automatically log you out and and disconnect your session if there has been no activity for a certain amount of time. Use this command to ask the server to set its idle limit to the given number of seconds. Omit the number to ask the server to inform you of its current idle limit.

    FTP STATUS [ filename ]
    Asks the FTP server to send information about the current session. The result is a free-format report that might include server identification, username and login time, FTP protocol settings, and file-transfer statistics. If a filename is given, the server is supposed to send detailed information about the file.

    FTP SYSTEM
    Asks the FTP server to identify its operating system (Listed in Internet Assigned Numbers, Operating System Names). Examples: UNIX, VMS, VM/CMS, WINDOWS-NT. Unfortunately many variations are allowed (e.g. LINUX-2.0, LINUX-2.2, FREEBSD, ULTRIX, etc, instead of UNIX; WINDOWS-NT-3, WINDOWS-NT-3.5, WINDOWS-NT-3.51, WINDOWS-NT-4, etc). The report might also include other information like "Type L8", "Type I", or "Type A", indicating the file-transfer mode.

    FTP HELP [ keyword [ keyword [ ... ] ]
    Asks the server to list the commands it supports. The response is usually cryptic, listing FTP command mnemonics, not the commands used by the client (since the server has no way of knowing anything about the client's user interface). For example, the PUT command is STOR in FTP protocol. If a keyword is given, which should be an FTP protocol command, slightly-more- detailed help is given about the corresponding command (if the FTP server supports this feature). Examples: "ftp help", "ftp help stor".

    FTP SITE text
    (Advanced) Sends an FTP SITE (site-specific) command. Usually this means that the FTP server is asked to run an external command with the given arguments. You might be able to find out what SITE commands are available by sending "ftp help site" to the server, but in general the availability of and response to SITE commands is (not surprisingly) site specific.

    FTP QUOTE text
    (Advanced) Sends an FTP command in FTP protocol format. Use this command to send commands to the server that the FTP client might not know about.

    SHOW FTP
    Lists client (Kermit) FTP settings and information. Also SHOW CONNECTION, SHOW COMMUNICATIONS.

    HELP FTP [ keyword ]
    Asks Kermit to list and describe its built-in FTP commands.

    HELP SET FTP [ keyword ]
    Asks Kermit to list and describe its built-in SET FTP commands.

    [ Top ] [ FTP Top ] [ C-Kermit Home ] [ Kermit Home ]

    3.1.5. Making Proxy Connections

    The simplist form of firewall traversal is the HTTP CONNECT command. The CONNECT command was implemented to allow a public web server which usually resides on the boundary between the public and private networks to forward HTTP requests from clients on the private network to public web sites. In order to allow secure web connections to be established, the CONNECT command works by authenticating the client with a username/password and then establishing a tunnel to the desired host.

    Many web servers support the CONNECT command and it can be configured to allow outgoing connections to authenticated user to any TCP/IP hostname/port combination accessible to the web server. The limitations of HTTP CONNECT is that it can only be used for outgoing connections for protocols that are implemented using TCP/IP. Protocols such as Kerberos authentication that use UDP/IP cannot be tunneled using HTTP CONNECT.

    Kermit provides support for the use of HTTP CONNECT proxy services with the command:

      SET TCP HTTP-PROXY [/USER:username /PASSWORD:password] hostname/ip-address[:port]
    

    When a port is not specified the default port configured on the HTTP server is used. This is frequently port 443. When a hostname is specified, it is resolved using the DNS available to the web server.

    3.2. Making Secure FTP Connections

    Also see: Accessing IBM Information Exchange with Kermit.

    In the previous section, you can see several examples of traditional insecure authentication: username and password sent across the network in clear text. Of course this is bad practice on at least two counts: (1) storing passwords in files (such as script files) gives access to the target systems to anybody who can obtain read access to your scripts; and (2) sending this information over the network leaves it open to interception by network sniffers or compromised hosts.

    Because of the increasing need for security on the Internet, FTP servers are beginning to appear that offer secure forms of authentication, in which no information is sent over the network that would allow anyone who intercepts it to usurp your identity and gain your access rights.

    Kermit provides an equivalent form of FTP security for each type of IETF standard security implemented in Telnet. These include GSSAPI-KERBEROS5, KERBEROS4, Secure Remote Password (SRP), and Transport Layer Security (SSL and TLS). It does not presently include SSL tunneling nor any form of SSH v1 or v2. When Kermit is built with the necessary libraries, secure FTP connections are attempted by default, in which all connections are authenticated and the command and data channels are private.

    The use of authentication and encryption for FTP connections can be adjusted with the commands listed below, which are available only if your version of Kermit was built with the corresponding security options and libraries:

    SET FTP AUTHTYPE { AUTOMATIC, GSSAPI-KRB5, KERBEROS4, SRP, SSL, TLS }
    Specifies an ordered list of authentication methods to be attempted when AUTOAUTHENTICATION is ON. The default list is: GSSAPI-KRB5, SRP, KERBEROS_V4, TLS, SSL. If none of the selected methods are supported by the server, an insecure login is used as a fallback. Note, by the way, that SSL or TLS can be used to secure an anonymous connection.

    SET FTP AUTOAUTHENTICATION { ON, OFF }
    Tells whether authentication should be negotiated by the FTP OPEN command. Default is ON. Use SET FTP AUTOAUTHENTICATION OFF to force a clear-text, unencrypted connection to FTP servers (such as the one at the Kermit FTP site) that normally would try to negotiate secure authentication and encryption.

    SET FTP AUTOENCRYPTION { ON, OFF }
    Tells whether encryption (privacy) should be negotiated by the FTP OPEN command, which can happen only if secure authentication is also negotiated. Default is ON.

    SET FTP AUTOLOGIN { ON, OFF }
    Tells Kermit whether to try logging in automatically when you make an FTP connection, as opposed to letting you do it "by hand" with the FTP USER command.

    SET FTP COMMAND-PROTECTION-LEVEL { CLEAR, CONFIDENTIAL, PRIVATE, SAFE }
    Determines the level of protection applied to the command channel:

      CLEAR         Data is sent in plaintext and not protected against tampering.
      CONFIDENTIAL  Data is encrypted but not protected against tampering.
      PRIVATE       Data is encrypted and is protected against tampering.
      SAFE          Data is sent in plaintext but protected against tampering.
    

    The default is PRIVATE.

    SET FTP CREDENTIAL-FORWARDING { ON, OFF }
    Tells whether end-user credentials are to be forwarded to the server if supported by the authentication method (GSSAPI-KRB5 only). This is often required to allow access to distributed file systems (e.g. AFS.)

    SET FTP DATA-PROTECTION-LEVEL { CLEAR, CONFIDENTIAL, PRIVATE, SAFE }
    Tells what level of protection is applied to subsequent data channels. The meanings of the protection-level keywords are the same as for SET FTP COMMAND-PROTECTION-LEVEL. The default is PRIVATE.

    SET FTP SRP CIPHER name
    Specifies the cipher to be used for encryption when SRP authentication is in use. The list of possible choices is computed based on the capabilities of the local SRP library and includes NONE plus zero or more of the following:

      BLOWFISH_ECB        CAST5_ECB          DES_ECB          DES3_ECB 
      BLOWFISH_CBC        CAST5_CBC          DES_CBC          DES3_CBC
      BLOWFISH_CFB64      CAST5_CFB64        DES_CFB64        DES3_CFB64
      BLOWFISH_OFB64      CAST5_OFB64        DES_OFB64        DES3_OFB64
    

    The default is DES3_ECB.

    SET FTP SRP HASH name
    Specifies the hash to be used for data protection when SRP authentication is in use. The choices are MD5 and SHA. The default is SHA.

    Command-line options:

    -k name
    Specifies the realm to be used with Kerberos 4 authentication (= SET AUTH K4 REALM name).

    -f
    Enables forwarding of Kerberos 5 credentials to the host when using GSSAPI authentication (= SET AUTH K5 FORWARDABLE ON).

    -x
    Enables autoencryption (= SET FTP AUTOENCRYPTION ON).

    -c cipher
    Specifies the kind of cipher to be used for encryption with SRP authentication. Equivalent to SET FTP SRP CIPHER, with the same choices. If this option is not given, CAST5_CBC is used.

    -H hash
    Specifies the hash to be used for encryption with SRP authentication. Equivalent to SET FTP SRP HASH, with the same choices. If this option is not given, SHA is used.

    -z debug
    Turns on SSL/TLS debugging.

    -z secure
    Requires secure connection.

    -z certsok
    Says to accept all certificates without checking validity.

    -z verify=n
    Sets certificate verification mode to the given number, n:
      0 = no verification
      1 = verify certificate if presented
      2 = require verification of certificate

    -z cert=filename
    Specifies a file containing a client certificate to be presented to the FTP server.

    -z key=filename
    Specifies a file containing a private key matching the client certificate.

    -z !krb4
    (nokrb4) Disables the use of Kerberos 4.

    -z !gss
    -z nogss
    Disables the use of GSSAPI - Kerberos 5.

    -z !srp
    -z nosrp
    Disables use of SRP.

    -z !ssl
    -z nossl
    Disables the use of SSL.

    -z !tls
    -z notls
    Disables the use of TLS.

    Caution: If your FTP connection is secured via AUTH TLS, it is not possible to interrupt a file transfer. This is a limitation of all known FTP servers that support AUTH TLS.

    Note that when using certain security methods, such as SSL or TLS, you may be prompted to confirm or verify certain actions or conditions, for example, whether to accept self-signed certificates. This can interfere with unattended operation of scripts; see Section 3.10.

    [ Top ] [ FTP Top ] [ C-Kermit Home ] [ Kermit Home ]

    3.3. Setting FTP Preferences

    FTP preferences can be set globally and persistently with the commands in the following sections; many of these can also be overridden on a per-command basis with switches that have the same name.

    3.3.1. Logs, Messages, and Other Feedback

    You can control the amount of feedback received from your FTP session with the commands in this section. First, you can create a log of your FTP transfers with the following commands:

    SET TRANSACTION-LOG { VERBOSE, FTP, BRIEF }
    Selects the log format. VERBOSE is the default, and is described in the manual. FTP chooses a WU-FTPD format, the same as is used by the popular FTP server. BRIEF creates per-file records in comma-separated-list format. For greater detail, see Section 4.17 of the C-Kermit 7.0 Update Notes.

    LOG TRANSACTIONS filename
    Records FTP (or Kermit, or any other protocol) uploads and downloads in the given file using the format selected by the most recent SET TRANSACTION-LOG command, if any, or else the default format.

    FTP screen messages and displays are controlled by the following commands:

    SET TRANSFER DISPLAY { FULLSCREEN, CRT, SERIAL, BRIEF, NONE, OFF }
    FTP transfers use Kermit's normal file-transfer display styles. Use this command to choose the desired format; the default on most platforms is FULLSCREEN. The display is automatically disabled if Kermit is running in the background or in batch. BRIEF is always used for command-line initiated transfers (unless suppressed by -q). While a file-transfer is in progress, you can interrupt it in the normal Kermit way by typing one of the following keys or key combinations:
      X - Cancel current file but go on to the next one (if any).
      Z - Cancel the entire transfer.
      Ctrl-L or Ctrl-W - Refresh the file-transfer display (if any).

    SET FTP DISPLAY { FULLSCREEN, CRT, SERIAL, BRIEF, NONE, OFF }
    Like SET TRANSFER DISPLAY, but applies only to FTP connections, and does not affect Kermit- or other protocol file transfers.

    SET QUIET { ON, OFF }
    This command applies to Kermit in general, not just FTP. OFF by default; when ON, it suppresses most messages from most commands as well as the file-transfer display.

    SET FTP PROGRESS-MESSAGES { ON, OFF }
    Tells whether Kermit should print locally-generated feedback messages for each non-file-transfer command. ON by default.

    SET FTP VERBOSE-MODE { ON, OFF }
    Tells whether to display all responses from the FTP server. OFF by default. This shows all responses to all commands, except when the file-transfer display is active, and unless you have SET QUIET ON. When OFF, responses are shown only for commands such as FTP PWD whose purpose is to display a response.

    SET FTP DEBUG { ON, OFF }
    Tells whether local client debugging information should be displayed. OFF by default. When ON, the commands that are sent to the server are shown, as well as its responses (even if VERBOSE-MODE is OFF), plus additional informational messages are printed regarding the progress of secure operations. Also, the temporary file created by the MGET command is not deleted so you can see what's in it.

    Set all of these to OFF when silent running is desired.

    3.3.2. Operational Preferences

    FTP DISABLE new-protocol-feature-name
    FTP ENABLE new-protocol-feature-name
    Explained in Section 3.11.

    SET FTP AUTOLOGIN { ON, OFF }
    If you give this command prior to opening an FTP connection, it controls whether Kermit tries to log you in automatically as part of the connection process. Normally ON, which means the username and password are sent automatically (and prompted for if they are not yet known). When OFF, FTP OPEN connects to the server without logging in. OFF is equivalent to the -n command-line option when using Kermit's FTP command-line personality. See Section 3.1.4 for usage.

    SET FTP PASSIVE-MODE { ON, OFF }
    ON by default, to avoid random TCP port assignment for data connections, which can prevent FTP protocol from working through firewalls and network address translators (for more on these topics, see the Kermit security reference. Set to OFF in case the FTP server does not support passive mode, or in case the client has problems with it (it has been observed, for example, that when using passive mode, the SCO XENIX 2.3.4 TCP/IP stack hangs in the connect() call forever). Synonyms: PASSIVE [ ON ], PASSIVE OFF, PASV [ ON ], PASV OFF.

    SET FTP SEND-PORT-COMMANDS { ON, OFF }
    This command determines whether the FTP client sends a new PORT command to the server when accepting incoming data connections (as when not using passive mode.) When PASSIVE-MODE is OFF and SET SEND-PORT is OFF, the port that was originally specified is reused. This is the default behavior for normal FTP clients but it is not compatible with many firewalls.

    SET FTP CHARACTER-SET-TRANSLATION { ON, OFF }
    Whether to translate character sets when transferring files with FTP (explained in Section 3.7). OFF by default.

    SET FTP SERVER-CHARACTER-SET name
    Tells Kermit the character set used by the FTP server, UTF-8 by default (Section 3.7).

    SET FTP SERVER-TIME-OFFSET delta-time
    Tells Kermit to apply the given delta time to file timestamps provided by the server for its files; for use when (for example) the server does not have its timezone set correctly.

    SET FTP ERROR-ACTION { PROCEED, QUIT }
    When transferring a group of files with FTP, and an error occurs with one of the files, Kermit normally goes on the next file. Use SET FTP ERROR-ACTION to QUIT to make Kermit stop the transfer immediately and fail if an error occurs with any single file in the group. Example: you have given Kermit a list of files to send, and one of the files can not be found, or read permission is denied. Note that canceling a file by typing 'X' during transfer is not considered an error (if you want to cancel the entire transfer, type 'Z' or Ctrl-C).

    SET FTP PERMISSIONS { AUTO, ON, OFF }
    When uploading files with PUT or MPUT, this tells whether Kermit should send each file's permissions. The default is OFF, which means not to send permissions, in which case the uploaded file's permissions are set by the FTP server according to its own criteria. ON means to send them, AUTO means to send them only if the client (Kermit) and server are on like platforms (e.g. both UNIX). This command has no effect when downloading, since the FTP protocol does not include a way for the server to inform the client of a file's permissions. Also see FTP PUT /PERMISSIONS. Note that setting permissions after uploading is likely to work (correctly or at all) only when the client and server platforms are alike (e.g. both of them are some form of UNIX). Also note that Windows files don't have permissions. Also see FTP CHMOD.

    SET FTP DATES { ON, OFF }
    When downloading files with GET or MGET, this tells whether Kermit should try to set the received file's date from the server's date. FTP DATES is ON by default. Note, however, that FTP protocol does not allow date preservation when uploading. So at best, SET FTP DATES ON can work only when downloading, and then only when the server agrees to furnish file dates.

    SET FTP FILENAMES { AUTO, CONVERTED, LITERAL }
    When uploading (sending) files, this tells whether to convert outbound filenames to "common form". This means allowing only one period in a name, uppercasing any lowercase letters, replacing spaces by underscores, etc. AUTOMATIC is the default, meaning LITERAL when client and server are the same type of system (e.g. UNIX) and CONVERTED otherwise. Special case: if the setting is AUTOMATIC and the client is not UNIX and the server identifies itself as UNIX, Kermit uses a less-strict form of conversion, in which lowercase letters are not uppercased and the filename can contain any number of periods, but spaces are still converted to underscore. When receiving, conversion generally means to change all-uppercase names to lowercase and spaces to underscore.

    SET FTP UNIQUE-SERVER-NAMES { ON, OFF }
    Applies only to uploads. Tells the server to create new, unique names for incoming files that have the same names as existing files. OFF by default, in which case the server overwrites existing files with new files of the same name. When ON, the server uses its own built-in method for creating new names for incoming files; for example, appending a period (.) and a number to the name. CAUTION: Use this option only if you do not need to refer to the file after it is uploaded, since FTP protocol provides no mechanism for the client to find out what name was assigned by the server.

    SET FTP COLLISION { ... }
    When downloading, what to do if an incoming file has the same name as an existing file. Options are the same as for SET FILE COLLISION. If this command is not given, Kermit's regular FILE COLLISION setting is used. If this command is given, it overrides the FILE COLLISION setting for FTP transfers only. See Section 3.6.2 for details.

    SET FTP TYPE { TEXT, BINARY, TENEX }
    Changes the default transfer mode. When sending (uploading) files, this command has no effect unless you disable automatic text/binary mode switching (Section 4) with SET FILE SCAN OFF or SET TRANSFER MODE MANUAL. When receiving (downloading) files, this command establishes the transfer mode to be used when a filename does not match any of Kermit's text or binary filename patterns, unless you use SET FTP GET-FILETYPE-SWITCHING or SET TRANSFER MODE MANUAL to disable automatic switching, in which case, this command establishes the transfer mode for all downloaded files. In all cases, however, the FTP TYPE can be overridden in any GET or PUT command by including a /TEXT (/ASCII), /BINARY, or /TENEX switch. The FTP TYPE is independent of the Kermit FILE TYPE setting. TENEX is used for sending 8-bit binary files to 36-bit platforms such as TOPS-10, TOPS-20, and TENEX, and getting them back again. Synonym: ASCII = TEXT. Note: there is also an FTP TYPE command, which does what SET FTP TYPE does but also sends a TYPE command to the server immediately if the given type is different from the current one.

    If you want want specific FTP preference settings to be in effect for all your Kermit FTP sessions, put the desired SET FTP commands in your Kermit customization file (~/.mykermrc in UNIX, K95CUSTOM.INI in Windows).

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    3.4. Managing Directories and Files

    In Kermit, commands for directory and file management can refer to:

    (There can also be an HTTP connection, but the commands in this section don't apply to HTTP connections.)

    Thus in general, each such command comes in three forms:

    1. With no prefix in C-Kermit 8.0.200, it refers to the local computer (CD, DIR, etc). In C-Kermit 8.0.201 and later, however, the "locus" switches to automatically to the remote FTP server when you make an FTP connection (see the SET LOCUS description Section 7); thus C-Kermit 8.0.201 acts almost exactly like a regular FTP client when it has an FTP connection, yet still acts like itself on other kinds of connections.

    2. With the REMOTE prefix, it is for a Kermit server (REMOTE CD, REMOTE DIR).

    3. With the FTP prefix, it's for an FTP server (FTP CD, FTP DIR).

    4. Also see Section 3.8, which explains "R-commands" and "L-commands".

    Kermit's FTP file and directory management commands are as follows. When an R-command is included in the Synonyms list, be sure to read Section 3.8 about rules for use of R-commands.

    FTP CD [ directory ]
    Tells the FTP server to change its default (working) directory to the one given, which usually must be expressed in the syntax of the server platform (UNIX, VMS, etc). If the directory is not specified, the result depends on the FTP server -- it might complain that the command is illegal, or it might change to your original login directory. Synonyms: FTP CWD (Change Wording Directory); RCD.

    FTP CDUP
    Tells the FTP server to change its default (working) directory to the parent directory of its current one (equivalent to "cd .." in UNIX, or "cd [-]" in VMS). Synonyms: RCDUP, FTP UP.

    FTP PWD
    Asks the FTP server to report ("print") its current working directory. Synonym: RPWD.

    FTP MKDIR directory
    Asks the FTP server to create the directory whose name is given. In general, the name must be in the syntax of the server's file system, and it must be either absolute (a full pathname) or relative to the server's current (working) directory. This command fails if the directory can't be created for any reason, including that it exists already. Synonym: RMKDIR.

    FTP RMDIR directory
    Asks the FTP server to remove the directory whose name is given. The rules are the same as for MKDIR, plus in most cases, the server will not remove any directory unless it is empty. Synonym: RRMDIR.

    FTP DIRECTORY [ filespec ] [ redirectors ]
    Tells the FTP server to send a directory listing of the specified files. If no filespec is given, the server lists all files in its current working directory. The results are in whatever format the server chooses to send them. You can use UNIX-like redirectors to send the listing to a file or a pipeline, exactly as with the regular Kermit client/server REMOTE DIRECTORY command (Using C-Kermit, Chapter 11). Synonym: RDIRECTORY. Examples:

        ftp dir                           ; Show listing of all files on screen
        ftp dir *.txt                     ; List *.txt files on screen
        ftp dir *.txt > somefile          ; Put listing in somefile
        ftp dir *.txt >> somefile         ; Append listing to somefile
        ftp dir *.txt | sort > somefile   ; Put sorted listing in somefile
        ftp dir | more                    ; Runs list through "more"
        ftp dir | sort | more             ; Runs list through "sort" and "more"
    

    FTP VDIRECTORY [ filespec ] [ redirectors ]
    "Verbose" directory. This is an alternative FTP DIRECTORY command primarily for use with DECSYSTEM-20 (TOPS-20) FTP servers, which send only filenames when given a DIRECTORY command; the VDIRECTORY command makes them also send file sizes, dates, and attributes.

    FTP CHECK filespec
    Asks the FTP server whether the given file exists or, if the filespec contains wildcards, if any files match, and this command succeeds or fails accordingly. FTP CHECK fails if given the name of an existing directory. The only way to check if a remote directory exists is to try to FTP CD to it.

    FTP MODTIME filename
    Asks the FTP server, via the not-yet-standard FTP MDTM command, to send the modification date and time of the given file. The response should be a numeric string in the format: yyyymmddhhmmssxxxxx... where yyyy is the year, mm is the month, dd is the day, hh is the hour (0-23), mm is the minute, ss is the second, and xxx... is the optional fraction of the second (0 or more digits). The date and time is expressed in UTC (GMT, Zulu, Zero-Meridian). The result is available programmatically in the \v(ftp_message) variable, and is understandable by Kermit's date-time switches and functions. For example, suppose we want to upload all local files that are newer than a particular file on the server:

      C-Kermit> ftp modtime signpost
      C-Kermit> echo \v(ftp_message)
      20010807113542.014
      C-Kermit> ftp mput /after:\v(ftp_message)GMT *
    

    Note that we must append "GMT" to the date-time string to let the /AFTER switch know the time is GMT rather than local.

    FTP SIZE filename
    Asks the FTP server to send the size (in bytes) of the given file. The result might vary depending on whether the current FTP TYPE is binary or text ("ascii"). For a reliable byte count, do FTP TYPE BINARY first. The result is available programmatically in the \v(ftp_message) variable.

    FTP CHMOD permissions filename
    Tells the FTP server to set the permissions (protection) of the given file to the ones given. The permissions and filename must be given in whatever syntax is required by the server. Example (for a UNIX-based FTP server):

      ftp chmod 664 oofa.txt
    

    Not all servers support this command. For non-UNIX-based servers, you might need to use FTP QUOTE or FTP SITE and the appropriate platform-specific FTP server command.

    FTP UMASK [ number ]
    This command is probably specific to UNIX-based servers; it sets the UNIX "umask", which is the default permissions mask for new (in this case, incoming) files. Crudely put, the UNIX umask is an octal representation of a binary number in in which a 1 bit stands for a permission bit that must be 0, and a 0 bit stands for a permission bit that can be 0 or 1 depending on other factors, such as the permissions of the parent directory. Example: "umask 007" requires that new files are created without read/write/execute world permission. If the number is not specified, the server's current umask is reported.

    FTP RENAME filename newname
    Asks the FTP server to rename the file whose name is "filename" to "newname". Works only for one file; can not be used with wildcards. The server's interpretation of "newname" can vary (in some cases it must be a filename, in others perhaps it can also be a directory name, in which case if the filename denote a regular file, the file might be moved to the given directory). Some servers might allow files to be renamed ("moved") between physical disks or partitions, others might not. Synonym: RRENAME.

    FTP DELETE [ switches ] filespec [ filespec [ ... ] ]
    Tells the FTP server to delete the file or files listed. Each file specification may, but need not, contain wildcard characters to match multiple files. File specifications and wildcard syntax must be those of the server. Any file specifications that contain spaces must be enclosed in braces or doublequotes. FTP DELETE switches are:

     /ERROR-ACTION:  /FILENAMES:     /NOBACKUPFILES  /QUIET
     /EXCEPT:        /LARGER-THAN:   /NODOTFILES     /NOPAGE
     /PAGE           /RECURSIVE      /SMALLER-THAN:
    

    When used with FTP DELETE, the /RECURSIVE switch deletes files but not directories, and furthermore depends on the server providing recursive file lists, which is not the normal behavior. For further details, see the descriptions of these switches in Section 3.6. Synonyms: FTP MDELETE (Kermit makes no distinction between DELETE and MDELETE); RDELETE.

    FTP TYPE { TEXT, BINARY, TENEX }
    Tells the FTP server to change its file-transfer type to the one given, immediately. See SET FTP TYPE for details.

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    3.5. Uploading Files With FTP

    Uploading means sending files from the client (Kermit) to the FTP server. The basic command for uploading files with FTP is PUT:

    FTP PUT [ switches ] [ filespec [ as-name ] ]
    Uploads (sends) the file or files that match the file specification, which may include wildcards, to the server. If no filespec is given, the names of files to send are taken from the /LISTFILE: file, if any, otherwise from the SEND-LIST, if any. Unless you go out of your way to prevent it, Kermit determines the transfer mode (text or binary) for each file automatically, and switches automatically on a per-file basis. If an as-name is given, the file is sent under that name instead of its own (if an as-name is given with a wildcard filespec, the result is a bit more complicated, and is explained later in this section).

    Unlike normal FTP clients, Kermit does not prompt you by default (or at all) for each file; it just sends them, just as it does with Kermit protocol. The filespec can be a literal filename or a Kermit pattern, described in:

      http://www.kermitproject.org/ckermit70.html#x4.9
    

    Kermit patterns are equivalent to C-Shell patterns and provide a fair amount of flexibility in selecting which files to send, which is augmented by the file-selection switches presented in Section 3.5.1.

    FTP MPUT [ switches ] filespec [ filespec [ ... ] ]
    FTP MPUT is just like FTP PUT except it allows you to give more than one file specification, and it does not allow an as-name in the file list. However, as-names can be given to either PUT or MPUT with the /AS-NAME: switch.

    If a PUT or MPUT command results in one file being uploaded, it succeeds if the file is uploaded completely and fails otherwise. If more than one file is selected for upload, success or failure depends on the FTP ERROR-ACTION setting; if it is PROCEED (the default setting), then the [M]PUT command succeeds if at least one of the files was completely uploaded, and fails otherwise, If FTP ERROR-ACTION is QUIT, the [M]PUT command succeeds if all selected files were uploaded successfully, and fails if any file failed.

    FTP uploads may be interrupted just like Kermit uploads. While the transfer is in progress, type:

      X to interrupt the current file and go on to the next file.
      Z to cancel the current file and all remaining files.
      ^C (Control-C): Like Z, but might act more quickly.
    

    MPUT may be used as in regular FTP clients, but it is not required to send multiple files; in Kermit it is required only if you want to give multiple file specifications. Examples:

      ftp put oofa.txt               ; Send a single file oofa.txt
      ftp put oofa.txt budget.txt    ; Send single file oofa.txt as budget.txt
      ftp put *.txt                  ; Send all *.txt files
      ftp mput *.txt                 ; Send all *.txt files (same as "put *.txt")
      ftp mput *.txt foo.bar         ; Send all *.txt files plus foo.bar
    

    The distinction between PUT and MPUT is important only when more than one filespec is given, just like the distinction between Kermit SEND and MSEND:

      ftp put oofa.txt budget.txt    ; Send oofa.txt AS budget.txt
      ftp mput oofa.txt budget.txt   ; Send oofa.txt AND budget.txt
    

    If the source file specification includes any path segments, for example:

      put /tmp/oofa.txt
      put subdir/another/andanother/oofa.txt
    

    the path portion is stripped from the filename that is sent to the server. However, if an as-name contains a path, it is retained. Examples:

      ftp put /usr/doc/oofa.txt      ; Send as "oofa.txt".
      ftp put oofa.txt /tmp/oofa.txt ; Send as "/tmp/oofa.txt"
    

    The latter example sends the file oofa.txt from your current local directory to the server's /tmp directory. This works only if the server uses the same directory notation that you used in the as-name AND the given directory already exists on the server AND if you have write access to it.

    Use caution when uploading from a case-sensitive file system, such as UNIX, to a file system that is not case sensitive, such as Windows or VMS. If you have two files in UNIX, AA and aa and upload both of them, the second one will overwrite the first. The only way around this provided by FTP protocol is its "unique server names" feature (SET FTP UNIQUE-SERVER-NAMES or the /UNIQUE switch described below).

    3.5.1. FTP PUT Switches

    FTP PUT and MPUT are similar in format and behavior to the regular Kermit SEND and MSEND commands, and they allow most of the same optional switches:

    C-Kermit>ftp put ? Filename, or switch, one of the following:
     /after:                 /larger-than:           /rename-to:
     /array:                 /listfile:              /server-character-set:
     /as-name:               /local-character-set:   /server-rename-to:
     /before:                /move-to:               /simulate
     /binary                 /nobackupfiles          /smaller-than:
     /command                /nodotfiles             /tenex
     /delete                 /nofollowlinks          /text
     /dotfiles               /not-after:             /transparent
     /error-action:          /not-before:            /type:
     /except:                /permissions:           /update
     /filenames:             /quiet                  /unique-server-names
     /filter:                /recover
     /followlinks            /recursive
    

    Since most of these switches are common to Kermit's SEND and MSEND commands, they described only briefly here. For greater detail see:

      http://www.kermitproject.org/ckermit70.html#x1.5 (explanation of switches)
      http://www.kermitproject.org/ckermit70.html#x4.7 (file-transfer switches)

    First the file-selection switches:

    /AFTER:date-time
    /BEFORE:date-time
    /NOT-AFTER:date-time
    /NOT-BEFORE:date-time
    Only send those files modified on or after or before the given date and time. These switches can be combined to select files modified between two date/times. Various date-time formats are accepted; if the date-time contains spaces, it must be enclosed in braces or doublequotes. See http://www.kermitproject.org/ckermit70.html#x1.6 and Section 8.13 of this document for details about date-time formats. Examples:
      ftp put /after:{1 jan 2000 0:00:00} *
      ftp put /after:-5days *
    

    /LARGER-THAN:number
    /SMALLER-THAN:number
    Only send files larger (smaller) than the given number of bytes (octets). These switches can be combined to select files in a certain size range.

    /TYPE:{TEXT,BINARY}
    Only send files that are the given type, which is determined for each file just before sending it by file scanning. BINARY includes TENEX; if you have included a /TENEX switch, or previously given a [SET] FTP TYPE TENEX command, binary files are sent in TENEX, rather than BINARY mode.

    /[NO]DOTFILES
    [Don't] include files whose names begin with dot (.). By default, such files are not included unless your filespec explicitly mentions them.

    /NOBACKUPFILES
    Don't include files whose names end with .~nnn~, where nnn is a number, e.g. oofa.txt.~27~. These are backup files created by Kermit, EMACS, and other applications. By default, backup files are included.

    /NOFOLLOWLINKS
    (UNIX only) Skip over symbolic links rather than following them (default). This applies to wildcard and/or recursive [M]PUTs; if a single filename is given, and it happens to be a symbolic link, the file it points to is sent.

    /FOLLOWLINKS
    (UNIX only) Always follow (resolve) symbolic links, even in wildcard or recursive [M]PUTs. Use with caution. Watch out for circular links, endless loops, etc.

    /EXCEPT:pattern
    Exception list -- don't send files whose names match the given pattern. See Section 1.5.4 of the C-Kermit 7.0 Update Notes for details. If you want to exclude a directory from a recursive [M]PUT, use /EXCEPT:{dirname/*}.

    /RECURSIVE
    Sends the desired files from the current (or given) directory, plus all directories beneath it, including empty directories, replicating the directory structure on the server. No special capabilities are required in the server, but of course your login ID on the server must have the appropriate access and permission to create directories. Recursive PUTs work not only between like platforms (e.g. UNIX to UNIX) but also between unlike ones (e.g. UNIX to VMS or Windows), in which case text-file format differences are handled by Kermit's automatic text/binary mode switching (Section 4) and character-set translation (Section 3.7). Synonym: /SUBDIRECTORIES.

    /UPDATE
    Send only files that have changed since last time (Section 3.5.2).

    /ARRAY:arrayname
    The "file" to be sent is an array, or a segment of one, rather than a real file. In this case the other selection switches don't apply. The array contents are sent in text mode, and each array element is treated as a line. Example:
      ftp put /as-name:array.txt /array:&a
    
    (or, to send a segment of the array, /array:&a[100:199]). If you don't include an /AS-NAME, a name of "_array_x_" is used (where x is the array letter). If you include this switch, most other switches are meaningless and ignored.

    /COMMAND
    The "file" to be sent is the standard output of a command, rather than a real file. It is sent in text or binary mode according to the prevailing FTP TYPE, which can be overridden with a /TEXT or /BINARY switch. Example: Example:
      ftp put /command /as-name:{userlist} {finger | sort -r}
    

    /LISTFILE:filename
    Tells Kermit to obtain the list of files to be sent from the file whose name is given. This file must contain one file specification (which may be wild) per line. If the list includes files from different directories, such as a recursive listing of a directory tree, the paths are recreated on the server (if possible) if you include the /RECURSIVE switch; otherwise all the files are sent to the current directory on the server.

    Now the other switches:

    /AS-NAME:text
    If a single file is being sent, send it with the given text as its name. If multiple files are being sent, the text must be a template that includes variables such as \v(filename), \v(filenumber), \v(ntime), to allow dynamic creation of each name. The same applies to the as-name field of the FTP PUT command. If this switch is not included (and an as-name is not included as the second filename to PUT), each file is sent with its own name.

    /BINARY
    /TEXT
    /TENEX
    Forces this upload to take place in the given mode, regardless of the current FTP TYPE setting, and without automatic text/binary switching. /ASCII is a synonym for /TEXT.

    /FILTER:command
    Specifies that the file(s) is/are to be passed through the given command or pipeline on their way to the server. Example:

      ftp put /binary /filter:{gzip -c \v(filename)} /as-name:\v(filename).gz *
    

    /TRANSPARENT
    /LOCAL-CHARACTER-SET:name
    /SERVER-CHARACTER-SET:name
    Character-set translation for text files, explained in Section 3.7.

    /ERROR-ACTION:{PROCEED,QUIT}
    Overrides the prevailing FTP ERROR-ACTION for the duration of this PUT or MPUT command only.

    /RECOVER
    Resume an interrupted transfer where from the point of interruption (explained in Section 3.5.2). Synonym: /RESTART.

    /DELETE
    Tells Kermit to delete each source file immediately after, and only if, it has been uploaded completely and successfully. This, in effect, moves the file from the client to the server.

    /MOVE-TO:directory
    Tells Kermit to move each source file to the named local directory after, and only if, it has been uploaded completely and successfully.

    /RENAME-TO:template
    Tells Kermit to rename each (local) source file according to the given template after, and only if, it has been uploaded completely and successfully. The template works as in /AS-NAME.

    /SERVER-RENAME-TO:template
    Tells Kermit to ask the server to rename each file according to the given template as soon as, and only if, it has been received completely and successfully. The template works as in /AS-NAME. Requires write and rename access on the server, so doesn't usually work with (e.g.) anonymous uploads to public incoming areas where the permissions don't allow renaming. Examples:

    ftp mput /server-rename:\v(filename).ok *
    Appends ".ok" to each filename on the server when it's finished uploading.

    ftp mput /as-name:\v(filename).tmp /server-rename:\v(filename) *
    This is the reverse of the previous example; it uses a temporary name while uploading is in progress and reverts the file to its real name when uploading is complete.

    ftp mput /as-name:\v(filename) /server-rename:../final/\v(filename) *
    Moves the file from the working directory to a final directory when the upload is complete, but in this case you have to know the pathname syntax of the server. If the rename fails, the [M]PUT command fails according to the FTP ERROR-ACTION selection.

    /FILENAMES:{AUTOMATIC,CONVERTED,LITERAL}
    Overrides the FTP FILENAMES setting for this upload only.

    /PERMISSIONS:{ON,OFF}
    Overrides the FTP PERMISSIONS setting for this upload only.

    /UNIQUE
    Tells Kermit to tell the server to give unique names to incoming files that would otherwise overwrite existing files that have the same name. This switch conflicts with /UPDATE, /RECOVER, /PERMISSIONS, and /SERVER-RENAME since the client has no way of knowing the name assigned by the server.

    /QUIET
    Don't display file-transfer progress or statistics.

    /SIMULATE
    Shows which files would be sent without actually sending them. Useful (for example) with /UPDATE (next section). The results are shown in the file-transfer display (if it is not disabled) and in the transaction log (if one is active). Hint: use SET TRANSFER DISPLAY BRIEF.

    3.5.2. Update Mode

    When you include the /UPDATE switch, this means to skip sending any file that already exists on the server if the local file's modification date/time is not later than that of the corresponding file on the server. Here is a typical application for update mode: Suppose that on Computer A, you maintain a large set of files (say, a collection of Web pages and graphics images, or the source files for a software application), and you need to keep a parallel copy on another Computer, B. Of course you could upload the entire collection every day:

      cd source-directory
      ftp computerb.xyzcorp.com
      ( authentication details... )
      ftp cd target-directory
      ftp put [ switches ] *
    

    But if the total size is large or the network slow, this would be unnecessarily time-consuming. Worse, if other users or sites had to update whenever new files appeared in B's directory, this would cause them unnecessary work. By including the /UPDATE switch:

      ftp put /update [ other-switches ] *
    

    only those files that changed since last time are uploaded. Here's how it works. For each local file that is selected for uploading:

    All time comparisons take place in Coordinated Universal Time (UTC)(1), also known as GMT or Zulu time: Timezone 0; standard time, without daylight savings.

    WARNING: Some FTP servers, such as Novell NWFTPD.NLM, ignore or misimplement the FTP specification and send local time rather than UTC.

    Update mode is useful only when always used in the same direction. When you upload (PUT) a file with FTP, the destination file receives the current timestamp on the server's computer, not the original file's timestamp (2). If you try to FTP PUT /UPDATE the same file again, it will be skipped (as expected) since the remote copy is newer. However, if you try to FTP GET /UPDATE the same file (Section 3.6), it will be transferred for the same reason.

    To check the availability of PUT /UPDATE on a particular connection, issue an FTP MODTIME command for a file that is known to exist on the server. If it succeeds, PUT /UPDATE should work and in that case, you can run a procedure like the one above every day: the first time, it sends all the files; after that, it sends only the ones that changed. If a transaction log is active, a notation is included for any files that are skipped.

    Notes:

    1. Why is Coordinated Universal Time abbreviated UTC? From the National Institute of Standards and Technology FAQ: "In 1970 the Coordinated Universal Time system was devised by an international advisory group of technical experts within the International Telecommunication Union (ITU). The ITU felt it was best to designate a single abbreviation for use in all languages in order to minimize confusion. Since unanimous agreement could not be achieved on using either the English word order, CUT, or the French word order, TUC, the acronym UTC was chosen as a compromise."

    2. The Kermit FTP client is unusual in that, when downloading only, it can set the received file's date from the file's date on the server, but this should not affect the update feature. When uploading to an FTP server, however, there is no mechanism for the client to set the date of the uploaded file on the server.

    3.5.3 Recovery

    Suppose that while you are uploading a large file over a slow connection, the connection is lost before the entire file is transferred. With most FTP clients, you would have to start over, thus resending the portion of the file that was sent already, and that is already on the server. But Kermit's /RECOVER switch (Synonym: /RESTART) lets you continue an interrupted transfer from the point of failure, thus transferring only the part that wasn't sent already. The prerequisites for recovery are:

    Here's how it works. When you include the /RECOVER switch:

    If the switch is accepted, then for each selected file:

    To safeguard file integrity, recovery is not attempted unless all the preconditions are met. For the widest possible usefulness, APPEND is used rather than RESTART. For stream transfers (the only kind that Kermit supports) the results are the same.

    By design, the /RECOVER switch can be included with any FTP PUT or MPUT command, even if it specifies a group of files. This allows you to resume an interrupted batch transfer from where it left off. The files that were already completely sent are skipped, the file that was interrupted is recovered, and the remaining files are uploaded.

    By the way, it doesn't matter how the original partial file was uploaded -- FTP, Kermit, Zmodem, etc: as long as the preconditions are met, it can be recovered with FTP PUT /RECOVER, or for that matter also using Kermit protocol and SEND /RECOVER.

    A word of caution, however, when the original upload was in text mode with character-set translation (Section 3.7):

    Kermit has no way of knowing anything about the previous upload. As a safeguard, an error occurs if you include /RECOVER and also specify a character-set of UCS2 or UTF8, since recovery can't possibly work in that situation. Otherwise, it's up to you to avoid unsafe recovery operations.

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    3.6. Downloading Files With FTP

    Although uploading files with Kermit's FTP client is just as easy and flexible as sending files with Kermit protocol, the same is not always true for downloading because FTP servers lack some of the capabilities of a Kermit server:

    The commands for downloading are:

    SET FILE DOWNLOAD-DIRECTORY [ directory ]
    As with Kermit transfers, this command, if given, tells C-Kermit where to store incoming files in the absence of a specific as-name. If not given, incoming files are stored as indicated by the as-name, if any, otherwise in the current directory, just as with Kermit transfers. The more verbose transfer display formats give the full pathname of each received file, and, in case you have trouble finding a downloaded file afterwards, its full path is also listed in the transaction log (if you kept one), and you can also ask Kermit where it went with the WHERE command.

    SET FTP GET-FILETYPE-SWITCHING { ON, OFF }
    ON by default, causing Kermit to switch automatically into text or binary mode for each file based on whether its name matches a text pattern or binary pattern. Set this OFF, or use a /TEXT, /BINARY, or /TENEX switch to defeat this feature. Use SHOW PATTERNS to see the current pattern list.

    [ FTP ] GET [ switches ] filename [ as-name ]
    Asks the server to send the given file, and if it comes, stores it locally under the given as-name, if any, otherwise under its original name (modified according to the selected filename conversion option), in your download directory, if you have specified one, otherwise in the directory indicated in the as-name, if any, otherwise in your current directory. If you accidentally use a wildcard in the filename ("get *.txt") the server will reply with a message like "File not found" (unless there is a file whose name actually is "*.txt"). If FTP GET-FILETYPE-SWITCHING is ON, and in the absence of any GET switches to override it, the file is transferred in binary mode if it matches any of Kermit's binary name patterns, and in text mode if it matches any of Kermit's text name patterns, and in the prevailing FTP TYPE if it matches none of these patterns.

    [ FTP ] MGET [ switches ] filespec [ filespec [ filespec [ ... ] ] ]
    Like GET, but for multiple files. One or more file specifications can be given, and any or all (or none) of them can contain wildcards or can be directory names. The file list may not include an as-name, but you can still give one with the /AS-NAME: switch.

    In both the FTP GET and MGET commands, any filenames that contain spaces must be enclosed in braces or doublequotes (see Section 5 for details).

    FTP downloads may be interrupted just like Kermit transfers. While the transfer is in progress, type:

    Before proceeding, a brief word about temporary files. In FTP protocol, the MGET command works by requesting a file list from the server, and then (internally) issuing a GET command (FTP RETR protocol directive) for each file. The file list returned by the server can be any size at all, so in case it is huge, we don't store it in memory; instead we put it in a temporary file. For troubleshooting purposes, you should be aware of two points:

    1. The location of the temporary file is chosen according the TMP or TEMP environment variables. If neither of these variables is defined, you might need to define it. In case there is not enough space on the indicated disk or partition for the server's file list, you might need to either clean up the temporary area, or redefine the environment variable to indicate a different area that has sufficient space.

    2. If you want to look at the list yourself, use SET FTP DEBUG ON. This tells Kermit to (a) give you the full pathname of the temporary file at the end of each MGET command, and (b) not to delete it, as it normally does.

    3.6.1. FTP GET Switches

    The following switches are available with FTP GET and MGET:

    /TEXT
    Specifies a text-mode transfer. Overrides the global FTP TYPE setting and filename pattern-matching for the duration of the current command only, All files are downloaded in text mode. Synonym: /ASCII.

    /BINARY
    Specifies a binary-mode transfer. Overrides the global FTP TYPE setting and filename pattern-matching for the duration of the current command only. All files are downloaded in binary mode.

    /TENEX
    Like /BINARY but specifies a special binary transfer mode to be used when getting 8-bit binary files from a 36-bit platform such as TOPS-10, TOPS-20, or TENEX. All files are downloaded in the special binary mode.

    /RECOVER
    This instructs Kermit to try to recover an incomplete download from the point of failure. Works only in binary mode, and only if the server supports the (not-yet-standard) FTP "REST" directive. See Section 3.6.3 for details. Synonym: /RESTART.

    /FILENAMES:{CONVERTED,LITERAL}
    Overrides the FTP FILENAMES (filename conversion) setting for this download only, forcing incoming filenames to be either converted or taken literally.

    /AS-NAME:text
    For GET, this is equivalent to giving an as-name after the filename. For MGET, this is the only way to specify alternative names for the incoming files. With MGET, the /AS-NAME text should (must) contain a Kermit variable, usually \v(filename) or \v(filenumber). Example:

      mget /text /as-name:\v(filename).new *.c
    

    This gets all ".c" files and stores them with ".new" appended to their names. See the C-Kermit 7.0 Update Notes for details.

    /COMMAND
    This specifies that the incoming file is to be written to the standard input of a command, rather than to a file. The command name is the as-name from the GET command or the /AS-NAME argument. If you need to refer to the incoming file's name in the command, use \v(filename). See the description of the regular Kermit GET /COMMAND command for details and examples.

    /QUIET
    Transfers the files quietly; don't put up a file-transfer display.

    /ERROR-ACTION:{QUIT,PROCEED}
    This switch affects only MGET. If an error occurs with a particular file, this tells whether to go on to the next file (PROCEED) or to stop right away and fail (QUIT). The default is PROCEED.

    The file selection switches are:

    /EXCEPT:{pattern} or /EXCEPT:{{pattern}{pattern}{...}}
    Exception list for MGET; skip downloading any file whose name matches any of the given patterns (when using the second format, up to 64 patterns may be specified). CLICK HERE for syntax details.

    /SMALLER-THAN:number
    Download only files whose size is smaller than the given number of bytes (octets). Requires that the FTP server support the SIZE or MLSD directive.

    /LARGER-THAN:number
    Download only files whose size is greater than the given number of bytes. Requires that the FTP server support the SIZE or MLSD directive.

    /NOBACKUPFILES
    During MGET, don't download any files whose names end with backup suffixes (.~n~ where n is a number).

    /NODOTFILES
    During MGET, don't download any files whose names begin with period (.). Equivalent to /EXCEPT:{.*}.

    /LISTFILE:local-filename
    The given file contains a list of files to GET, one per line. Filenames in the listfile can contain wildcard characters in the syntax of the server. There is no limit on the number of lines in the listfile.

    /NAMELIST:local-filename
    If this switch is given, then instead of actually retrieving the selected files, the GET command retrieves a list of the names of the files that would be retrieved, and places it in the specified file. The resulting file is an ordinary text file, with one filename per line, suitable for reading by a person, or processing by a computer program, including Kermit itself (FOPEN / FREAD / FWRITE / FCLOSE), and as /FILELIST: file. If the filename is omitted or given as "-" (dash, hyphen), the list goes to the screen. NOTE: if you want a copy of the complete list sent by the server, use SET FTP DEBUG ON, perform an MGET, and the temporary file containing the list will be kept rather than deleted (and Kermit tells you its name).

    /UPDATE, /COLLISION:keyword
    Explained in Section 3.6.2.

    /RECURSIVE
    This means to try to download an entire directory tree, rather than just files from a particular directory. In fact, FTP protocol does not provide a method to request a recursive download (unless the server supports MLSD; see Section 3.11), so this works only if the FTP server does it anyway, without being asked, as some do. In this case, Kermit detects that names in the returned file list contain directory separators, and therefore attempts to create the needed directories as the files arrive. But this can work only if the server is on the same kind of platform as the client, so the pathname syntax can be recognized, and also because the server does not switch between text and binary mode, which would be vital for cross-platform transfers. Use with caution. Synonym: /SUBDIRECTORIES.

    Even when the server does not provide recursive file lists, [M]GET /RECURSIVE forces Kermit to replicate any directory structure implied or expressed by the server's file list. For example:

      get somepath/somefile
    

    Gets the file named somefile from the server's somepath directory and puts it Kermit's current (or download) directory, whereas:

      get /recursive somepath/somefile
    

    creates the path locally and then puts the file in it. Similarly for MGET:

      mget */data/*
    

    downloads all the files in all the data subdirectories of all the subdirectories of the server's current directory and stores them locally in Kermit's current (or download) directory, whereas:

      mget /recursive */data/*
    

    re-creates the server's directory structure locally.

    The FTP protocol does not include explicit mechanisms for recursion, so Kermit builds upon what is available. Although an Internet draft describes a mechanism ("MLSD") that would allow protocol-driven recursion, similar to Kermit's File Attribute packets (circa 1984), it has not yet attained RFC or standard status, and servers are not yet widely available that offer this feature. In the meantime, the effectiveness of MGET /RECURSIVE depends on the FTP server implementation. If the server returns a recursive list in response to the standard NLST command (whose behavior is ill-defined), Kermit's FTP MGET /RECURSIVE command uses it to re-create the remote directory tree locally. If the server supports MLSD, C-Kermit 8.0.206 and Kermit 95 2.1 and later are able to sense it automatically and use it, as described below in Section 3.11.

    The /BEFORE:, /AFTER:, /NOT-BEFORE:, and /NOT-AFTER: switches are not available for downloading because of the confusion with timezones. Would the given times be in the local timezone, the server's timezone, or GMT? The FTP server's directory listings show its own local times but since we don't know what timezone the server is in, there's no way to reconcile our local times with the server's. Similarly, /PERMISSIONS can't be preserved in downloads because FTP protocol provides no means of querying the server for a file's permission.

    Source-file disposition switches:

    /DELETE
    Each file that is downloaded successfully is to be deleted from the server. Requires the appropriate file access rights on the server.

    /SERVER-RENAME-TO:template
    Asks the server to rename each (remote) source file immediately after, and only if, it is sent correctly. See PUT /SERVER-RENAME-TO: for details.

    Destination-file disposition switches:

    /TO-SCREEN
    Displays the incoming file on the screen rather than storing it on disk. If this switch is given, the /RENAME-TO and /MOVE-TO switches are ignored, the file-transfer display is suppressed, and the given file(s) is/are shown on the screen. Can be used with /FILTER, e.g.

      get /text /to-screen /filter:more oofa.txt
    

    In fact, you should always use /TO-SCREEN with /FILTER or /COMMAND when the command would result in displaying the incoming file on the screen; otherwise C-Kermit would have no way of knowing to suppress its file transfer display (since it can't be expected to know what the command or filter does).

    /RENAME-TO:template
    Each file that is downloaded is to be renamed as indicated if and only if it was received completely and without error. The template can be literal text or can contain variables that are evaluated for each file. For MGET, the text must contain variables; for GET it can be a literal string. The \v(filename) variable contains the name of the current file, so:

      ftp mget /rename-to:\v(filename).ok *
    

    causes each file that is successfully downloaded to have ".ok" appended to its name. For details see Section 4.1 of the C-Kermit 7.0 Update Notes.

    /MOVE-TO:text
    Just like /RENAME-TO:, except the text denotes the name of a directory to which successfully downloaded files are to be moved. If the directory does not exist, it is created.

    The file transfer display does not show the /MOVE-TO or /RENAME-TO value, since the incoming file has not yet been moved or renamed.

    3.6.2. Filename Collisions

    What should happen if an incoming file has the same name as an existing file in the same directory? By default, Kermit's FILE COLLISION setting applies: BACKUP, RENAME, UPDATE, DISCARD, etc, as described in Using C-Kermit. Kermit's default FILE COLLISION setting is BACKUP (rename the existing file and store the incoming file under its own name) and therefore this is also the default FTP collision action.

    The name under which an incoming file is to be stored is determined as follows:

    If the resulting name coincides with the name of a local file that already exists, we have a filename collision. Collisions are handled according to the currently selected collision action:

    SET FTP COLLISION { BACKUP, RENAME, UPDATE, DISCARD, APPEND, OVERWRITE }
    This establishes a filename collision for FTP, separate from the Kermit one. The initial FTP collision setting is inherited from Kermit's FILE COLLISION setting when the first FTP command is given, but subsequent changes to Kermit's FILE COLLISION setting do not affect the FTP COLLISION setting. SHOW FTP tells the current FTP COLLISION setting.

    FTP GET /COLLISION:{BACKUP,RENAME,UPDATE,DISCARD,APPEND,OVERWRITE}
    Overrides the current FTP COLLISION action for this download only.

    FTP GET /UPDATE
    This is equivalent to GET /COLLISION:UPDATE, and is included for symmetry with PUT /UPDATE

    FTP GET /UPDATE and /COLLISION:UPDATE mean to download only those files whose modification dates on the server are later than those on the client. Date-time comparisons are done in Coordinated Universal Time (UTC, GMT, ZULU). The command:

    FTP MGET /COLLISION:APPEND /AS-NAME:newfilename *.*

    Downloads all matching remote files into a single local file (in whatever order the server sends them).

    3.6.3. Recovery

    Recovery is available for downloads too, but there are some differences from the uploading case described in Section 3.5.3:

    Here's how download recovery works:

    If the /RECOVER switch is accepted, then for each selected file:

    The /RECOVER switch can be included with any FTP GET or MGET command, even if it specifies a group of files. This lets you resume an interrupted batch transfer from where it left off. The files that were already completely sent are skipped, the file that was interrupted is recovered, and the remaining files are uploaded. BUT... unlike with uploading, where this can be done with any mixture of text and binary files, when downloading, it can only be done if all the files are binary.

    It doesn't matter how the original partial file was downloaded -- FTP, Kermit, HTTP, Zmodem, etc: as long as the preconditions are met, it can be recovered with FTP [M]GET /RECOVER, or for that matter also with GET /RECOVER (using Kermit protocol).

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    3.7. Translating Character Sets

    A possibly unique feature of Kermit's FTP client is its ability to convert character sets when transferring files in text mode, independent of the capabilities of the FTP server, as well as to translate the character sets of filenames regardless of transfer mode. For compatibility with existing FTP clients, and because there is a certain performance penalty, Kermit won't do this unless you ask for it. If you enable this feature, you need to inform Kermit of the character set (to be) used on the server and in some cases (explained below) also the local file character set. This discussion assumes you know a bit about character sets (as you must if you have to use them); see Chapter 16 of Using C-Kermit for a detailed treatment. The Kermit commands for FTP character-set conversion are:

    SET FTP CHARACTER-SET-TRANSLATION { ON, OFF }
    Whether to translate character sets when transferring text files with FTP. OFF by default. Set this to ON to enable character-set translation for subsequent FTP uploads and downloads.

    SET FTP SERVER-CHARACTER-SET name
    Text character set (to be) used by the server. Most FTP servers are ignorant of character sets, so all translations are done unilaterally by Kermit's FTP client. This means that when downloading files, you must know in advance the character-set used in the files you are downloading (and in their names). When uploading, you must specify the character-set to which local filenames and text-file contents are to be translated for transmission to the server. If you SET FTP CHARACTER-SET-TRANSLATION ON but do not specify an FTP SERVER-CHARACTER-SET, UTF8 is used, since this is the new Internet standard international character set; it is upwards compatible with ASCII and it encompasses most written languages and therefore does not favor any particular group of people, as any other default would do. If you SET FTP SERVER-CHARACTER-SET to something (anything) when FTP CHARACTER-SET TRANSLATION is OFF, this also sets the latter ON.

    SET FILE CHARACTER-SET name
    This is the regular Kermit (non-FTP-specific) command for identifying the character set (to be) used in local text files and filenames.

    TO REITERATE: If you SET FTP CHARACTER-SET TRANSLATION ON but do not specify an FTP SERVER-CHARACTER-SET, outbound text files are converted to UTF-8 and inbound text files are assumed to be UTF-8. If this is not appropriate, be sure to also specify the desired FTP SERVER-CHARACTER-SET.

    You can use "special" (non-ASCII) characters in filenames in all the client / server file management commands (FTP MKDIR, RMDIR, DIRECTORY, VDIRECTORY, DELETE, etc), and also in file-transfer commands. When giving commands such as FTP DIR (RDIR) and FTP PWD (RPWD), the reply is translated too, so you can read it. In this example, the client and server use entirely different codes to represent the special characters of German:

      C-Kermit> ftp xyzcorp.de /anonymous
      C-Kermit> set ftp server-character-set latin1
      C-Kermit> set file character-set german
      C-Kermit> rcd Städte
      C-Kermit> rpwd
      "/pub/ftp/Städte is current directory"
      C-Kermit> rdir
      -rw-rw----  1 olaf     54018 Jan  6 17:58 Adenbüttel.txt
      -rw-rw----  1 ursula     373 Jan  5 15:19 Aßlar.txt
      -rw-rw----  1 gisbert    482 Jan  5 15:20 Blowatz.txt
      -rw-rw----  1 gudrun     124 Jan  5 15:19 Böblingen.txt
      -rw-rw----  1 olga     14348 Jan  7 14:23 Köln.txt
    

    When the client and server file systems use different character sets, you should take care to use only those characters that the two sets share in common when creating filenames or text-file contents. For example, PC code pages contain a lot line- and box-drawing characters, and sometimes "smart quotes", etc, that are not found in ISO standard 8-bit character sets. You should be especially careful to avoid using such characters in filenames.

    [ C-Kermit Character Sets ]

    3.7.1. Character Sets and Uploading

    Kermit's PUT and MPUT commands include full file-scanning capabilities, as described in Section 4. Thus if FTP CHARACTER-SET-TRANSLATION is ON and your character-set associations are set up appropriately, Kermit automatically switches on a per-file basis between text and binary mode, and for each text file between your chosen 7-bit text character set (e.g. ASCII or ISO 646 German), 8-bit text (e.g. Latin-1 or Japanese EUC), UCS-2, and UTF-8, and converts each of these automatically to the server character-set, and furthermore automatically differentiates between the Little and Big Endian forms of UCS-2, always sending in Big Endian form.

    WARNING: It is not advisable to use UCS-2 (or any Unicode transformation other than UTF-8) "on the wire", i.e. as a server character set. Most FTP servers are not able to cope with it, since it contains lots of 0 (NUL) characters. If you do use it, Kermit does not translate filenames to or from UCS-2, for reasons well known to C programmers (for example, UNIX APIs assume filename strings are NUL-terminated). UTF-8 is the preferred (and standard) Unicode format for the Internet.

    FTP character-set translations differ from the regular Kermit ones by not restricting translations to a file-character-set / transfer-character-set pair. You can have Kermit's FTP client translate between any pair of character sets it knows about. You can see the list of supported character sets by typing either of the following:

      set ftp server-character-set ?
      set file character-set ?
    

    A typical list looks like this (CLICK HERE for an explanation of the names):

      C-Kermit>set file char ? One of the following:
       ascii            cp869-greek       hebrew-7         mazovia-pc
       british          cyrillic-iso      hebrew-iso       next-multinational
       bulgaria-pc      danish            hp-roman8        norwegian
       canadian-french  dec-kanji         hungarian        portuguese
       cp1250           dec-multinational iso2022jp-kanji  shift-jis-kanji
       cp1251-cyrillic  dg-international  italian          short-koi
       cp1252           dutch             jis7-kanji       spanish
       cp437            elot927-greek     koi8             swedish
       cp850            elot928-greek     koi8r            swiss
       cp852            euc-jp            koi8u            ucs2
       cp855-cyrillic   finnish           latin1-iso       utf8
       cp858            french            latin2-iso
       cp862-hebrew     german            latin9-iso
       cp866-cyrillic   greek-iso         macintosh-latin
      C-Kermit>
    

    Thus you can translate not only between private sets (like PC code pages) and standard ones (like Latin-1) as in Kermit protocol, but also between any given pair of private sets (e.g. CP852 and Mazovia). All conversions go through Unicode as the intermediate character set, resulting in a minimum of character loss, since Unicode is a superset of all other character sets known to Kermit.

    In addition to the SET commands listed above, the FTP PUT and MPUT commands include switches that apply only to the current command:

    /LOCAL-CHARACTER-SET:name
    /SERVER-CHARACTER-SET:name
    Use these switches to force a particular translation. These switches override the global FTP CHARACTER-SET-TRANSLATION and SERVER-CHARACTER-SET settings and also character-set differentiation by file scanning for the duration of the PUT or MPUT command. The file scan is still performed, however, to determine whether the file is text or binary; thus these switches do not affect binary files unless you also include the /TEXT switch to force all files to be treated as text.

    In other words, if you include one or both of these switches with a PUT or MPUT command, they are used. Similarly, the /TRANSPARENT switch disables character-set translation for the PUT or MPUT command despite the prevailing FTP CHARACTER-SET-TRANSLATION and SERVER-CHARACTER-SET settings.

    When uploading, the FILE CHARACTER-SET setting is ignored unless you have forced Kermit not to scan local files by including a /TEXT or /BINARY switch with your [M]PUT command, or by disabling automatic text/binary switching in some other way.

    Examples:

    1. Suppose you have a CP852 (East European) text file that you want to upload and store in ISO Latin Alphabet 2 encoding:

        ftp put /local-char:cp852 /server-char:latin2 magyar.txt
      

    2. Suppose you always want your text files converted to Latin-2 when uploading with FTP. Then put:

        set ftp server-character-set latin2
      

      in your Kermit customization file, and then you can omit the /SERVER-CHARACTER-SET: switch from your FTP PUT commands:

        ftp put /local-char:cp852 magyar.txt
      

    3. Now suppose that all the text files on your PC are written in Hungarian, but they have a variety of encodings, and you don't want to have to include the /LOCAL-CHARACTER-SET: switch on every FTP PUT command, or (more to the point) you want to be able to send a mixture of these files all at once. Put these commands in your Kermit customization file:

        set ftp server-character-set latin2            ; ISO 8859-2
        set file default 7-bit-character-set hungarian ; ISO 646 Hungarian
        set file default 8-bit-character-set cp852     ; PC East European Code Page
      

      and now PUT and MPUT will automatically detect and switch among ISO 646 Hungarian, Code Page 852, UTF-8, and UCS-2 encodings, translating each one to Latin-2 for uploading:

        ftp put *.txt
      

    And since binary files are also detected automatically, the latter can be simplified to:

      ftp put *
    

    even when "*" matches a diverse collection of binary and text files, because translations are skipped automatically for binary files.

    3.7.2. Character Sets and Downloading

    The commands and switches are the same as for uploading, but automatic character-set switching works differently, since Kermit can't scan the server files in advance. Instead, the transfer mode (text or binary) is based on the filenames; each name is compared with Kermit's list of text name patterns and binary name patterns. If the name matches a binary pattern (for example, if the filename is oofa.tar.gz and one of the filename patterns is "*.gz"), the file is downloaded in binary mode; otherwise if it matches a text pattern (e.g. oofa.txt matches "*.txt"), it is transferred in text ("ascii") mode. Otherwise, it is transferred in the prevailing FTP TYPE.

    In C-Kermit 8.0, the pattern lists used with FTP GET are not the same lists used with Kermit transfers, and can not be viewed with SHOW PATTERNS, nor adjusted with ADD and REMOVE TEXT-PATTERNS and BINARY-PATTERNS, or SET FILE TEXT-PATTERNS and BINARY-PATTERNS. Configuration of the FTP patterns list will be added in a future release.

    Examples:

    get /server-char:latin1 /local-char:cp850 Grüße.txt
    In this command, the filename contains special characters, which you enter using whatever character set your local computer uses, in this case PC Code Page 850 (cp850). The command tells Kermit (in case it didn't know already from its FILE CHARACTER-SET setting) that the local character set is cp850 and the server's character-set is ISO 8859-1 Latin Alphabet 1 (latin1). Kermit translates the filename from cp850 to latin1 and sends the latin1 name to the server. Since it's a text file (matches "*.txt"), its contents are translated to cp850 on arrival, and it is saved with a cp850 name.

    mget /text /server:latin1 /local:utf8 *.txt
    This command:
    • Tells C-Kermit that the server's files are encoded in ISO 8859-1 Latin Alphabet 1.
    • Tells C-Kermit to translate the incoming files into Unicode UTF-8 for storage.
    • Asks the server to send all ".txt" files in text mode.

    mget /server:latin1 /local:utf8 *
    Tells Kermit to get all files from the server's directory, switching between text and binary mode based on the filename. The names of all the files are translated (to UTF-8 in this case), but contents are translated (also to UTF-8) only for text files.

    Note that any pair of 8-bit character sets is likely to have some incompatibilities. Any characters in the source file that do not have equivalents in the destination file's character set are converted to question marks. This applies to both filenames and to text file contents.

    Also note that the server's ability to accept special characters in filenames depends on the particular server. For example:

      get Grüße.txt
    

    works with WU-FTPD, but:

      mget Grüß*.txt
    

    does not.

    3.7.3. RFC2640

    RFC2640, July 1999, specifies a method by which the FTP client and server can negotiate the use of UTF8. However, RFC2640-capable servers are rare to nonexistent at this writing, and in any case you don't need them to be able to transfer text in UTF8. C-Kermit lets you upload and download text files in any character set it knows about, converting to or from any other character set it knows about, without the knowledge, permission, or cooperation of the server, and regardless of its capabilities.

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    3.8. FTP Command Shortcuts

    C-Kermit's FTP client coexists with other C-Kermit functions by requiring the "ftp" prefix for each FTP-related command: FTP OPEN, FTP GET, FTP BYE, and so on. For interactive use, however, this can be rather awkward and sometimes surprising, for example when a GET command starts a Kermit GET rather than an FTP GET. In fact, many Kermit commands might just as easily apply to an FTP connection: GET, PUT (SEND), BYE, and CLOSE. The following command lets you choose how these commands are interpreted:

    SET GET-PUT-REMOTE { AUTO, KERMIT, FTP }
    Controls the orientation of GET, PUT, REMOTE and other file-transfer and client/server commands that might apply to either Kermit or FTP. The default setting is AUTO, meaning that these commands apply to FTP if an FTP connection is open, and to Kermit otherwise. KERMIT means they always apply to Kermit, FTP means they always apply to FTP.

    Here is a complete list of affected commands:

     Kermit Command               FTP Equivalent
      (none)                       FTP [ OPEN ]
      LOGIN                        FTP USER
      LOGOUT                       FTP RESET
      BYE                          FTP BYE
      FINISH                       FTP BYE
      CLOSE                        FTP BYE
      HANGUP                       FTP BYE
      BINARY                       FTP TYPE BINARY
      TEXT (or ASCII)              FTP TYPE ASCII
      SEND (or PUT)                FTP PUT
      MSEND (or MPUT)              FTP MPUT
      RESEND                       FTP PUT /RECOVER
      CSEND                        FTP PUT /COMMAND
      GET                          FTP GET
      MGET                         FTP MGET
      REGET                        FTP GET /RECOVER
      REMOTE HELP      (RHELP)     FTP HELP
      REMOTE CD        (RCD)       FTP CD (CWD)
      REMOTE PWD       (RPWD)      FTP PWD
      REMOTE DIRECTORY (RDIR)      FTP DIRECTORY
      REMOTE DELETE    (RDEL)      FTP DELETE
      REMOTE MKDIR     (RMKDIR)    FTP MKDIR
      REMOTE RMDIR     (RRMDIR)    FTP RMDIR
      REMOTE RENAME    (RRENAME)   FTP RENAME
      REMOTE TYPE      (RTYPE)     FTP TYPE
      REMOTE EXIT      (REXIT)     FTP BYE
    

    The commands in the right-hand column always access FTP. The commands in the left column can access either Kermit protocol or FTP:

    Note that file-management commands such as DIRECTORY, DELETE, CD, PWD, MKDIR, RMDIR, HELP, RENAME, COPY, TYPE, and so on, always apply locally, no matter what kind of connection you have. This is the opposite of most FTP clients, where these commands are intended for the server, and require an "L" prefix for local execution (e.g. "dir" gets a directory listing from the server, "ldir" gets a local directory listing). To illustrate with the CD command and a typical UNIX FTP client:

     Client   Server      Change Local Directory     Change Remote Directory
      FTP      FTP         lcd                        cd (cwd)
      Kermit   Kermit      cd                         rcd, remote cd
      Kermit   FTP         cd                         ftp cd, rcd, remote cd
    

    Also note that not all REMOTE commands are useful with FTP, since FTP servers do not offer the corresponding functions. These include:

    Finally note that command shortcuts do not apply to the HELP command. For help about an FTP command, use (for example) "help ftp delete", not "help delete" or "help rdelete".

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    3.9. Dual Sessions

    You can have an FTP session open at the same time as a regular Kermit SET LINE or SET HOST (terminal) session. In this case, the default SET GET-PUT-REMOTE AUTO setting should ensure that all "two-faced" commands like GET, PUT, REMOTE, HANGUP, BYE, etc, apply to the Kermit session, and all commands for the FTP session must include the FTP prefix. To be absolutely certain, you can use SET GET-PUT-REMOTE KERMIT.

      ftp foo.bar.baz.com
      if fail ...
      (log in)
      set host foo.bar.baz.com
      if fail ...
      (log in)
    

    Now you have both an FTP and Telnet connection to the same host (of course they could also be to different hosts, and you could also have a direct or dialed serial connection instead of a Telnet connection). Now assuming you have a Kermit server on the far end of the Kermit connection:

      rcd incoming      ; Changes Kermit server's directory (= REMOTE CD)
      ftp cd incoming   ; Changes FTP server's directory
      put oofa.txt      ; Sends a file on the Kermit connection
      ftp put oofa.txt  ; Sends a file on the FTP connection
      bye               ; Shuts down the Kermit connection
      ftp bye           ; Shuts down the FTP connection
    

    Note that PUT and SEND are synonyms for both FTP and Kermit connections.

    You can also establish dual sessions on the Kermit command line:

      kermit -j host1 -9 host2
    

    This makes a Telnet connection to host1 and an FTP connection to host2.

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    3.10. Automating FTP Sessions

    Most of Kermit's scripting features can be used to make and control FTP sessions: FOR and WHILE loops, IF-ELSE and SWITCH constructions, variables, arrays, built-in functions, and all the rest. You can't use INPUT, MINPUT, OUTPUT, CLEAR, or SCRIPT on an FTP session, but these are not needed since the FTP protocol is well defined.

    CLICK HERE for an FTP scripting tutorial.

    3.10.1. FTP-Specific Variables and Functions

    The following variable tells whether an FTP connection is open:

    \v(ftp_connected)
    1 if there is an active FTP connection, 0 if there isn't.

    The FTP OPEN command sets:

    \v(ftp_host)
    The host to which the most recent FTP connection was made.

    \v(ftp_security)
    The security method negotiated for the current FTP session. The value is "NULL" when no security is used. Other possibilities are GSSAPI, KERBEROS_V4, SSL, TLS, and SRP. Also see \v(authname), \v(authstate), and \v(authtype). See 3.2. Making Secure FTP Connections.

    \v(ftp_server)
    The OS type (UNIX, VMS, etc) of the FTP server host.

    The FTP USER command (or FTP OPEN /USER:, or FTP with automatic login) sets:

    \v(ftp_loggedin)
    1 if you are logged in to an FTP server, 0 if you are not.

    The current COMMAND-PROTECTION-LEVEL and DATA-PROTECTION-LEVEL values are reflected in:

    \v(ftp_cpl)
    \v(ftp_dpl)
    The values are "clear", "confidential", "safe" or "private". See 3.2. Making Secure FTP Connections.

    The FTP GET-PUT-REMOTE setting is reflected in:

    \v(ftp_getputremote)
    The values are "auto", "ftp", or "kermit".

    Every FTP command sets the \v(success) variable, as well as the following two FTP-specific variables:

    \v(ftp_code)
    The standardized numeric FTP protocol code from the server's response to the last client command, a 3-digit decimal number defined in RFC959. Briefly:

    1xx = Positive Preliminary Reply
    2xx = Positive Completion Reply
    3xx = Positive Intermediate Reply
    4xx = Transient Negative Completion Reply
    5xx = Permanent Negative Completion Reply

    \v(ftp_message)
    The text message, if any, from the server's response to the last client command. If the most recent response had multiple lines, this variable has only the final line. These messages are not standardized and vary in format and content from server to server. Synonym: \v(ftp_msg).
    FTP file transfers set the regular Kermit transfer status variables:

      \v(cps)         Characters per second of most recent transfer.
      \v(filespec)    File specification used in most recent transfer.
      \v(fsize)       Size of file most recently transferred.
      \v(tfsize)      Total size of file group most recently transferred.
      \v(xferstatus)  Status of most recent transfer (0 = success, 1 = failure).
      \v(tftime)      Elapsed time of most recent transfer, in seconds.
    

    During an FTP transfer, the per-file variables are:

      \v(filename)    Name of current file.
      \v(filenumber)  Ordinal file number in group (1, 2, 3, ...)
    

    3.10.2. Examples

    Let's begin with a simple example showing how to log in, send some files, and log out:

      define error if fail { ftp bye, stop 1 Error: \%1 }
      set transact brief
      log t
      ftp ftp.xyzcorp.com /anonymous
      if fail stop 1 Connection failed
      if not \v(ftp_loggedin) stop 1 Login failed
      ftp cd incoming
      error {ftp cd}
      cd upload
      error {local cd}
      ftp put /delete *
      error {put}
      ftp bye
    

    First we define an error handling macro to be used after the connection is made. Then we set up a brief-format transaction log to keep a record of our file transfers. Then we make a connection to the host and log in anonymously. The "if fail" command checks whether the connection was made. The "if not" command checks whether login was successful. Obviously the script should not continue unless both tests succeed.

    Next we change to the server's 'incoming' directory and to our own 'upload' directory, and send all the files that are in it (they can be any mixture of text and binary files), deleting each source file automatically after it is successfully uploaded. Each of these operations is checked with the ERROR macro, which prevents the script from continuing past a failure.

    Finally we close the FTP session with the "bye" command.

    Just like any other Kermit script, this one can be used in many ways:

    We could have used command shortcuts like "rcd", "put", and "bye", but since they can be ambiguous under certain circumstances, it is better to avoid them in scripts; they are intended mainly for convenience during interactive use. However, if you wish to use the shortcuts in a script, you can do it this way (error handling omitted for brevity):

      local \%t                       ; Declare a local temporary variable
      assign \%t \v(ftp_getputremote) ; Save current FTP GET-PUT-REMOTE setting
      set ftp get-put-remote ftp      ; Choose FTP orientation
      ftp xyzcorp.com /anonymous      ; Open an FTP connection
      get oofa.txt                    ; GET a file
      put foo.bar                     ; PUT a file
      rdel yesterday.log              ; Delete a file on the server
      bye                             ; Log out and disconnect from server.
      set ftp get-put-remote \%t      ; Restore previous GET-PUT-REMOTE setting
    

    Of course, FTP scripts can also be written as macros. This lets you pass parameters such as hostnames, usernames, and filenames to them:

      define doftpget {
          if < \v(argc) 4 end 1 Usage: \%0 host user remotefile [ localfile ]
          ftp \%1 /user:\%2
          if fail end 1 FTP OPEN \%1 failed
          if not \v(ftp_loggedin) end 1 FTP LOGIN failed
          ftp get {\%3} {\%4}
          if fail end 1 FTP GET \%3 failed
          ftp bye
      }
    

    Add this definition to your Kermit customization file, and it will always be available when you start Kermit. This macro lets you download a file with FTP by giving a single command, e.g.:

      doftpget xyzcorp.com anonymous oofa.txt
    

    3.10.3. Automating Secure FTP Sessions

    Often when making secure connections, you are prompted interactively for certain information or permission to proceed. These prompts can stop an automated procedure. To avoid them, you must give the appropriate commands to disable them, and/or supply the prompted-for information beforehand. Here are a few hints:

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    3.11. Advanced FTP Protocol Features

    The remainder of the FTP documentation (through the end of Section 3) is new to C-Kermit 8.0.206, but we leave it in black to prevent headaches. Except for titles.

    The new releases of C-Kermit (8.0.206) and Kermit 95 (2.1) support new FTP protocol features from RFC 2389 as well as most of what's in the Elz and Hethmon Extensions to FTP Internet Draft (see References). Some of these features, such as SIZE (request a file's size), MDTM (request file's modification time), and REST (restart interrupted transfer) have been widely implemented in FTP clients and servers for years (as well as in the initial release of the Kermit FTP clients). Others such as FEAT and MLSD are rarely seen and are new to the upcoming Kermit releases. TVFS (Trivial Virtual File Store) is supported implicitly, and the UTF-8 character-set is already fully supported at the protocol and data-interchange level.

    For Kermit users, the main benefit of the new FTP protocol extensions is the ability to do recursive downloads. But the extensions also introduce complications and tradeoffs that you should be aware of. Of course Kermit tries to "do the right thing" automatically in every case for backwards compatibility. But (as noted later) some cases are inherently ambiguous and/or can result in nasty surprises, and for those situations new commands and switches are available to give you precise control over Kermit's behavior, in case the defaults don't produce the desired results.

    3.11.1. Terminology

    Command-line FTP clients such as Kermit (as well as the traditional FTP programs found on Unix, VMS, ..., even Windows) have commands like PUT, MPUT, GET, MGET, and BYE, which they convert into zero or more FTP protocol commands, such as NLST, RETR, QUIT. For clarity, we'll use "command" to refer to commands given by the user to the FTP client, and "directive" for FTP protocol commands sent by the FTP client to the FTP server.

    3.11.2. Feature Negotiation

    New FTP protocol features are negotiated by the client sending a FEAT directive and the server responding with a list of (new) features it supports, or else with an error indication if it does not support the FEAT directive at all, in which case the client has to guess which new features it supports (Kermit guesses that it supports SIZE and MDTM but not MLST). Note that the MLST feature includes MLSD, which is not listed separately as a feature.

    Guessing is nice when it works, but sometimes it doesn't, and some FTP servers become confused when you send them a directive they don't understand, or they do something you didn't want, sometimes to the point of closing the connection. For this reason, Kermit lets you override default or negotiated features with the following new commands:

    FTP { ENABLE, DISABLE } FEAT
    Enables or disables the automatic sending of a FEAT directive upon connection to an FTP server. Note that FTP [ OPEN ] /NOINIT   also inhibits sending the FEAT directive (and several others) for the connection being OPEN'd, but without necessarily disabling FEAT for subsequent connections in the same Kermit instance. FEAT is ENABLED by default, in which case many FTP servers are likely to reply:

    500 'FEAT': command not understood
    

    which is normally harmless (but you never know). (In C-Kermit 8.0.208, this error message is suppressed unless you SET FTP DEBUG ON.)

    FTP ENABLE { MDTM, MLST, SIZE }
    Enables the given directive for implicit use by the FTP GET and MGET commands in case it has been disabled or erroneously omitted by the server in its FEAT response. Note: MLSD can be used in the FTP ENABLE and DISABLE commands as a synonym for MLST. YOU MUST GIVE THIS COMMAND AFTER MAKING THE FTP CONNECTION.

    FTP DISABLE { MDTM, MLST, SIZE }
    Disables implicit use of the given directive by GET or MGET in case it causes problems; for example, because it makes multifile downloads take too long or the server announces it erroneously or misimplements it. Use DISABLE FEAT before making a connection to prevent Kermit from sending the FEAT directive as part of its initial sequence. Note that disabling FEAT, SIZE, or MDTM does not prevent you from executing explicit FTP FEATURES, FTP SIZE, or FTP MODTIME commands. Also note that disabling SIZE prevents PUT /RESTART (recovery of interrupted uploads) from working. YOU MUST GIVE THIS COMMAND AFTER MAKING THE FTP CONNECTION.

    To enable or disable more than one feature, use multiple FTP ENABLE or FTP DISABLE commands. The SHOW FTP command shows which features are currently enabled and disabled.

    FTP FEATURES
    This command sends a FEAT directive to the server. In case you have been disabling and enabling different features, this resynchronizes Kermit's feature list with the server's. If the server does not support the FEAT directive, Kermit's feature list is not changed.

    FTP OPTIONS directive
    Informational only: the server tells what options, if any, it supports for the given directive, e.g. MLST. Fails if the server does not support the OPTS directive or if the directive for which options are requested is not valid. The directive is case-insensitive.

    FTP SIZE filename
    Sends a SIZE directive to the server for the given file. The filename must not contain wildcards. The server responds with an error if the file can't be found, is not accessible, or the SIZE directive is not supported, otherwise with the length of the file in bytes, which Kermit displays and also makes available to you in its \v(ftp_message) variable. If the directive is successful, Kermit (re-)enables it for internal use by the GET and MGET directives on this connection.

    FTP MODTIME filename
    Works just like the SIZE directive except it sends an MDTM directive. Upon success, the server sends modification date-time string, which Kermit interprets for you and also makes available in its \v(ftp_message) variable.

    Whenever a SIZE or MDTM directive is sent implicitly and rejected by the server because it is unknown, Kermit automatically disables it.

    3.11.3. Using MGET: NLST versus MLSD

    When you give an MGET command to an FTP client, it sends a request to the FTP server for a list of files, and then upon successful receipt of the list, goes through it and issues a RETR (retrieve) directive for each file on the list (or possibly only for selected files).

    With the new FTP protocol extensions, now there are two ways to get the list of files: the NLST directive, which has been part of FTP protocol since the beginning, and the new MLSD directive, which is new and not yet widely implemented. When NLST is used and you give a command like "mget *.txt", the FTP client sends:

    NLST *.txt
    

    and the server sends back a list of the files whose names match, e.g.

    foo.txt
    bar.txt
    baz.txt
    

    Then when downloading each file, the client sends SIZE (if it wants have a percent-done display) and MDTM (if it wants to set the downloaded file's timestamp to match that of the original), as well as RETR (to retrieve the file).

    But when MLSD is used, the client is not supposed to send the filename or wildcard to the server; instead it sends an MLSD directive with no argument (or the name of a directory), and the server sends back a list of all the files in the current or given directory; then the client goes through the list and checks each file to see if it matches the given pattern, the rationale being that the user knows only the local conventions for wildcards and not necessarily the server's conventions. So with NLST the server interprets wildcards; with MLSD the client does.

    The interpretation of NLST wildcards by the server is not necessarily required or even envisioned by the FTP protocol definition (RFC 959), but in practice most clients and servers work this way.

    The principal advantage of MLSD is that instead of sending back a simple list of filenames, it sends back a kind of database in which each entry contains a filename together with information about the file: type, size, timestamp, and so on; for example:

    size=0;type=dir;perm=el;modify=20020409191530; bin
    size=3919312;type=file;perm=r;modify=20000310140400; bar.txt
    size=6686176;type=file;perm=r;modify=20001215181000; baz.txt
    size=3820092;type=file;perm=r;modify=20000310140300; foo.txt
    size=27439;type=file;perm=r;modify=20020923151312; foo.zip
    (etc etc...)
    

    (If the format of the file list were the only difference between NLST and MLSD, the discussion would be finished: it would always be better to use MLSD when available, and the MGET user interface would need no changes. But there's a lot more to MLSD than the file-list format; read on…)

    The client learns whether the server supports MLSD in FEAT exchange. But the fact that the server supports MLSD doesn't mean the client should always use it. It is better to use MLSD:

    But it is better to use NLST:

    But when using MLSD there are complications:

    To further complicate matters, NLST can (in theory) work just like MLSD: if sent with a blank argument or a directory name, it is supposed to return a complete list of files in the current or given directory, which the client can match locally against some pattern. It is not known if any FTP server or client does this but nevertheless, it should be possible since this behavior can be inferred from RFC 959.

    In view of these considerations, and given the need to preserve the traditional FTP client command structure and behavior so the software will be usable by most people:

    1. The MGET command should produce the expected result in the common cases, regardless of whether NLST or MLSD is used underneath.

    2. For anomalous cases, the user needs a way to control whether the MGET argument is sent to the server or kept for local use.

    3. At the same time, the user might need a way to send a directory name to the server, independent of any wildcard pattern.

    4. The user needs a way to force NLST or MLSD for a given MGET command.

    By default, Kermit's MGET command uses MLSD if MLST is reported by the server in its FEAT list. When MLSD is used, the filespec is sent to the server if it is not wild (according to Kermit's own definition of "wild" since it can't possibly know the server's definition). If the filespec is wild it is held for local use to select files from the list returned by the server. If MLST is not reported by the server or is disabled, Kermit sends the MGET filespec with the NLST directive.

    The default behavior can be overridden globally with FTP DISABLE MLST, which forces Kermit to use NLST to get file lists. And then for situations in which MLSD is enabled, the following MGET switches can be used to override the defaults for a specific MGET operation:

    /NLST
    Forces the client to send NLST. Example:
    mget /nlst foo.*
    

    /MLSD
    Forces the client to send MLSD (even if MLST is disabled). Example:
    mget /mlsd foo.*
    

    /MATCH:pattern
    When this switch is given, it forces the client to hold the pattern for local use against the returned file list. If a remote filespec is also given (e.g. the "blah" in "mget /match:*.txt blah"), then it is sent as the NLST or MLSD argument, presumably to specify the directory whose files are to be listed. When the /MATCH switch is not given, the MGET filespec is sent to the server if the directive is NLST or if the filespec is not wild. Examples:

      Command:                   With NLST:     With MLSD:
        mget                      NLST           MLSD
        mget *.txt                NLST *.txt     MLSD        
        mget foo                  NLST foo       MLSD foo
        mget /match:*.txt         NLST           MLSD
        mget /match:*.txt foo     NLST foo       MLSD foo
    

    In other words, the pattern is always interpreted locally unless MGET uses NLST and no /MATCH switch was given.

    3.11.4. Examples

    3.11.4.1. Downloading a Single File

    There are no choices here, just use the FTP GET command. Kermit always sends the RETR directive, and possibly SIZE and/or MDTM. The small advantage of using MLST in this case is outweighed by the risk and effort of coding a special case.

    3.11.4.2. Downloading a Group of Files from a Single Directory

    This case presents tradeoffs, especially on slow connections:

    3.11.4.3. Downloading a Directory Tree

    MLSD is the only choice for recursive downloads; they rarely, if ever, work with NLST (the few cases where they do work rely on extra-protocol "secret" notations for the NLST argument). No special actions are required to force MLSD when the server supports it, unless you have disabled it. Examples:

    MGET /RECURSIVE
    This tells the server to send all files and directories in the tree rooted at its current directory.

    MGET /RECURSIVE *.txt
    This tells the server to send all *.txt files in the tree rooted at its current directory.

    MGET /MLSD /RECURSIVE *.txt
    Same as the previous example but forces Kermit to send MLSD in case it was disabled, or in case the server is known to support it even though it did not announce it in its FEAT listing.

    MGET /RECURSIVE /MATCH:*.zip archives
    Tells the server to send all ZIP files in the tree rooted at its "archives" directory.

    MGET /RECURSIVE /MATCH:* [abc]
    The server is running on VMS and you want it to send all the files in the directory tree rooted at [ABC]. But since "[abc]" looks just like a wildcard, you have to include a /MATCH: switch to force Kermit to send "[abc]" as the MLSD argument.

    In all cases in which the /RECURSIVE switch is included, the server's tree is duplicated locally.

    Although MLSD allows recursion and NLST does not, the MLSD specification places a heavy burden on the client; the obvious, straightforward, and elegant implementation (depth-first, the one that Kermit currently uses) requires as many open temporary files as the server's directory tree is deep, and therefore client resource exhaustion -- e.g. exceeding the maximum number of open files -- is a danger. Unfortunately MLSD was not designed with recursion in mind. (Breadth-first traversal could be problematic due to lack of sufficient navigation information.)

    Of course all of Kermit's other MGET switches can be used too, e.g. for finer-grained file selection (by date, size, etc), for moving or renaming files as they arrive, to override Kermit's automatic per-file text/binary mode switching, to pass the incoming files through a filter, to convert text-file character sets, and so on.

    3.11.4.4. NLST/MLSD Summary Table

    Here's a table summarizing MGET behavior when the server supports both NLST and MLSD. /NLST and /MLSD switches are included for clarity to indicate which protocol is being used, and the expected effects. In practice you can omit the /NLST and /MLSD switches and the Kermit client chooses the appropriate or desired protocol as described above. Sample commands presume a Unix file system on the server, but of course the server can have any file system or syntax at all.

    User's Command FTP Sends Remarks
    mget /nlst NLST Gets a list of all the files in the server's current and downloads each file. The list includes names only, so Kermit also must send SIZE and MDTM directives if size and timestamp information is required (this is always true of NLST). Sending NLST without an argument is allowed by the RFC959 NLST definition and by the Kermit FTP client, but might not work with other clients, and also might not work with every server.
    mget /nlst foo NLST foo If "foo" is a directory, this gets a list of all the files from the server's "foo" directory and downloads each file; otherwise this downloads the file named "foo" (if any) from the server's current directory.
    mget /nlst *.txt NLST *.txt Gets a list of the files in the server's current directory whose names match the pattern *.txt, and then downloads each file from the list. Because we are using NLST, we send the filespec (*.txt) to the server and the server interprets any wildcards.
    mget /nlst foo/*.txt NLST foo/*.txt  Gets a list of the files in the server's "foo" directory whose names match the pattern *.txt, and then downloads each file from the list (server interprets wildcards).
    mget /nlst /match:*.txt NLST Gets a list of all the files in the server's current directory and then downloads each one whose name matches the pattern *.txt (client interprets wildcards).
    mget /nlst /match:*.txt foo  NLST foo Gets a list of all the files in the server's "foo" directory and then downloads each one whose name matches the pattern *.txt (client interprets wildcards).
    mget /mlsd MLSD Gets a list of all the files from the server's current directory and then downloads each one. The list might include size and timestamp information, in which case Kermit does not need to send SIZE and MDTM directives for each file (this is always true of MLSD).
    mget /mlsd foo MLSD foo Gets a list of all the files from the server's "foo" directory (where the string "foo" does not contain wildcards) and then downloads each one. If "foo" is a regular file and not a directory, this command is supposed to fail, but some servers have been observed that send the file.
    mget /mlsd *.txt MLSD Gets a list of all the files from the server's current directory and then downloads only the ones whose names match the pattern "*.txt". Because we are using MLSD and the MGET filespec is wild, we do not send the filespec to the server, but treat it as though it had been given in a /MATCH: switch and use it locally to match the names in the list.
    mget /mlsd foo/*.txt MLSD This one won't work because MLSD requires that the notions of server directory and filename-matching pattern be separated. However, the client, which can't be expected to know the server's file-system syntax, winds up sending a request that the server will (or should) reject.
    mget /mlsd /match:*.txt MLSD Gets a list of all the files from the server's current directory and then downloads only the ones whose names match the pattern "*.txt" (client interprets wildcards).
    mget /mlsd /match:*.txt foo MLSD foo If "foo" is a directory on the server, this gets a list of all the files from the server's "foo" directory and then downloads only the ones whose names match the pattern "*.txt" (client interprets wildcards). This leaves the server CD'd to the "foo" directory; there's no way the client can restore the server's original directory because MLSD doesn't give that information, and since the client can not be expected to know the server's file-system syntax, it would not be safe to guess. If "foo" is a regular file, MLSD fails.
    mget /mlsd foo bar MLSD This one is problematic. You're supposed to be able to give MGET a list a filespecs; in this case we name two directories. The client must change the server's directory to "foo" to get the list of files, and then the files themselves. But then it has no way to return to the server's previous directory in order to do the same for "bar", as explained in the previous example.
    mget /mlsd /match:* [abc] MLSD [abc] Including a /MATCH: switch forces [abc] to be sent to the server even though the client would normally think it was a wildcard and hold it for local interpretation. In this example, [abc] might be a VMS directory name.
    mget /mlsd /match:* t*.h MLSD t*.h Contrary to the MLSD specification, some MLSD-capable FTP servers do interpret wildcards. This form of the MGET command can be used to force a wildcard to be sent to the server for interpretation.

    When MLSD is used implicitly (that is, without an /MLSD switch given to force the use of MLSD) and an MGET command such as "mget foo/*.txt" fails, Kermit automatically falls back to NLST and tries again.

    3.11.5. References

    1. Postel, J., and J. Reynolds, File Transfer Protocol (FTP), RFC 959, October 1985: ftp://ftp.isi.edu/in-notes/rfc959.txt.

    2. Hethmon, P, and R. Elz, Feature negotiation mechanism for the File Transfer Protocol, RFC 2389, August 1998: ftp://ftp.isi.edu/in-notes/rfc2389.txt.

    3. Elz, R, and P. Hethmon, Extensions to FTP, Internet Draft draft-ietf-ftpext-mlst-16.txt, September 2002: http://www.ietf.org/internet-drafts/draft-ietf-ftpext-mlst-16.txt.

    4. The Kermit FTP Client (overview).

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    4. FILE SCANNING

    A new feature called file scanning is used in various contexts to determine if a file is text or binary, and if it is text, what kind of text. The overhead of file scanning is surprisingly tolerable, usually about a quarter second per file. File scanning is now used instead of filename patterns unless you SET FILE SCAN OFF, which restores the previous behavior.

    The primary benefit of file scanning is in file transfer. For all practical purposes, now you can stop worrying about whether a file should be sent in binary or text mode, or about sending mixtures of text and binary files in a single operation, or configuring and fine-tuning your lists of binary-file and text-file name patterns: now it all just works.

    File scanning is done by the file sender, which determines the type of each file before it sends it and informs the receiver (Kermit or FTP server) of the type. File scanning is NOT done by the receiver, because it is the sender's responsibility to determine each file's type, send the file in the right mode, and inform the receiver of the mode. If both transfer partners are capable of this (or any other) form of automatic text/binary mode switching, then files can be sent in both directions with no worries about corruption due to inappropriate transfer mode. (As noted in Section 3, FTP servers don't do this, so this discussion does not apply when using Kermit to download from an FTP server.)

    The rest of this section is mainly for the curious. If you don't read it and simply accept all defaults, every file you send should go in the appropriate mode automatically. As always, however, for character-set translation to work for 7- and 8-bit character-set files, the appropriate SET FILE CHARACTER-SET command(s) must have been executed to identify their encoding (Kermit's default file character-set is neutral ASCII except on platforms like HP-UX or DG/UX, where the default file character-set is known). And of course, receiving is another matter -- obviously the other Kermit must also send each file in the appropriate mode.

    Scanning is more reliable than filename patterns simply because filenames are not reliable indicators of the file's contents. Classic examples include ".doc" files, which are binary if Microsoft Word documents but text on most other platforms, and ".com" files, which are binary on DOS and Windows but text on VMS. Anyway, nobody knows the naming conventions (if any) of all the applications (and persons!) on your computer. Scanning, on the other hand, determines each file's type by inspecting its contents rather than just looking at its name.

    Also, file patterns -- even when they work as intended -- categorize each file only as text or binary, whereas file scanning can make finer distinctions:

    BINARY
    Binary data, not to be converted in any way. Examples include binary machine code (executable programs), graphics images (GIF, JPG, etc), compressed files (Z, GZ, etc), archives and packages (ZIP, TAR, RPM, etc), object files and libraries (OBJ, DLL, etc).

    7-BIT TEXT
    Text encoded in a 7-bit character set such as ASCII or one of the ISO 646 national versions. Kermit has no way to tell which character is used, only that it's 7-bit text. Typical examples include program source code, README files, Perl or Kermit scripts, plain-text email, HTML, TeX, and various textual encodings of binary files: Hex, Base64, etc. When sending such files, the FILE DEFAULT 7BIT-CHARACTER-SET is used as the file character-set, and then the appropriate transfer character set is chosen from the associations list (ASSOCIATE, SHOW ASSOCIATIONS).

    8-BIT TEXT
    Text encoded in an 8-bit character set such as Latin-1, Latin-2, Latin/Hebrew, Latin/Cyrillic, KOI8, HP-Roman8, JIS X 0208, Code Page 437, or Code Page 1252. Again, Kermit has no way of knowing which particular set is in use, only that it's 8-bit text. When sending such files, the FILE DEFAULT 8BIT-CHARACTER-SET is used as the file character-set, and then the appropriate transfer character set is chosen from the associations list.

    UCS2 TEXT
    Unicode in its basic form, 16 bits (2 octets) per character. When sending such files, UCS2 is the file character-set and the byte order is identified automatically; the appropriate transfer character set is chosen from the associations list. Normally this would be UTF8. UTF-16 is not supported yet; Kermit's Unicode translations are restricted to Plane 0, the Base Multilingual Plane (BMP).

    UTF8 TEXT
    Unicode in its 8-bit transformation format. When sending such files, UTF8 is the file character-set; the appropriate transfer character set is chosen from the associations list, normally UCS2 or UTF8.

    File scanning is available in UNIX C-Kermit, in K-95, and to a limited extent, in VMS C-Kermit (full scanning is problematic in VMS because even plain-text files might contain binary record-format information). The relevant commands are:

    SET TRANSFER MODE { AUTOMATIC, MANUAL }
    Tells whether the file-transfer mode (text or binary) should be set by automatic or "manual" means. AUTOMATIC is the default, which allows any of the automatic methods that are enabled to do their jobs: FILE SCAN, FILE PATTERNS, peer recognition, etc. MANUAL lets you control the transfer mode with the SET FILE TYPE commands. As always, /TEXT and /BINARY switches on your file-transfer commands override all other methods; if you give one of these switches, scanning is not done. SHOW TRANSFER displays the current TRANSFER MODE setting.

    SET FILE SCAN { ON [ number ], OFF }
    Turns this feature on and off. It's ON by default. When OFF, the previous rules apply (SET FILE PATTERNS, etc). When ON is given, you can also specify a number of bytes to be scanned. The default is 49152 (= 48K). If a negative number is given, the entire file is scanned, no matter how big, for maximum certainty (for example, a PostScript file that appears to be plain text might include an embedded graphic past the normal scanning limit). SHOW FILE displays the current FILE SCAN setting.

    SET FILE DEFAULT 7BIT-CHARACTER-SET name
    Tells the 7-bit character-set to use if scanning identifies a 7-bit text file, e.g. GERMAN. SHOW FILE displays the current SET FILE DEFAULT settings. So does SHOW CHARACTER-SETS.

    SET FILE DEFAULT 8BIT-CHARACTER-SET name
    Tells the 8-bit character-set to use if scanning identifies an 8-bit text file, e.g. LATIN1. SHOW FILE and SHOW CHARACTER-SET display this.

    ASSOCIATE FILE-CHARACTER-SET fcs tcs
    When sending files and a file character-set (fcs) is identified by scanning, this tells C-Kermit which transfer character-set (tcs) to translate it to. It also allows C-Kermit to set the appropriate transfer character-set automatically whenever you give a SET FILE CHARACTER-SET command.

    ASSOCIATE TRANSFER-CHARACTER-SET tcs fcs
    When receiving files and a file arrives whose transfer character-set (tcs) is announced by the sender, this command tells C-Kermit which file character-set (fcs) to translate it to. It also allows C-Kermit to set the appropriate file character-set whenever you give a SET TRANSFER CHARACTER-SET command.

    SET FILE CHARACTER-SET name
    When given for a 7-bit set, also sets FILE DEFAULT 7BIT-CHARACTER-SET to the same set. When given for an 8-bit set, also sets FILE DEFAULT 8BIT-CHARACTER-SET to the same set. If an ASSOCIATE FILE-CHARACTER-SET command has been given for this set, also sets the corresponding transfer character-set.

    DIRECTORY /XFERMODE [ filespec ]
    Performs a file scan of the given files, listing the result for each file. If FILE SCAN is OFF but PATTERNS are ON, the result shown according to the current FILE TEXT-PATTERNS and BINARY-PATTERNS, and are restricted to (B) and (T). When FILE SCAN is ON, the results are:

      (B)          Binary
      (T)(7BIT)    Text: 7-bit
      (T)(8BIT)    Text: 8-bit
      (T)(UTF8)    Text: Unicode UTF8
      (T)(UCS2BE)  Text: Unicode UCS2 Big Endian
      (T)(UCS2LE)  Text: Unicode UCS2 Little Endian
    

    So you can use DIR /XFER to get a preview of how each file in a selected group will be transferred. Everything to the right of the (B) or (T) is new. If FILE SCAN is OFF, you only get the (B) or (T) as before.

    Note: Big and Little Endian refer to the ordering of bytes within a computer word. Big Endian architecture is standard and is used on most non-PC computers. Little Endian architecture is used on PCs.

    To illustrate file-transfer with scanning, suppose you have a directory containing a mixture of text and binary files, and each text file can be 7-bit German ISO 646, 8-bit Latin-1, or Unicode in any of the following forms: UCS2 Little Endian, UCS2 Big Endian, or UTF8 (UTF-16 is not supported yet). Assuming all the built-in defaults are in effect, the following three commands do the job:

      set file char german   ; This sets the default for 7-bit text files
      set file char latin1   ; This sets the default for 8-bit text files
      send *
    

    Each file is sent in the appropriate mode (text or binary), with text files converted to the appropriate transfer character-set and labeled so the receiver can convert them according to its own local conventions.

    By the way, what if you want to inhibit character-set translation but still allow automatic text/binary mode switching? Previously, you could simply SET TRANSFER CHARACTER-SET TRANSPARENT. But now with file scanning, the file and transfer character-sets are set automatically per file. A new command was added for this purpose:

    SET TRANSFER TRANSLATION { ON, OFF }
    Enables and disables file-transfer character-set translation. It is enabled by default.

    When TRANSFER TRANSLATION is OFF but FILE SCAN is ON, files are still scanned to see if they are text or binary, but no character-set translation is done when they text: only the normal record-format conversion.

    Like all SET commands, SET TRANSFER TRANSLATION is global and persistent. You can also force a particular file-transfer command (SEND, MSEND, GET, RECEIVE, TRANSMIT, etc) to not translate without affecting the global translation settings by including the new /TRANSPARENT switch, e.g.

      send /transparent oofa.txt
    

    As of C-Kermit 8.0.206, SET TRANSFER CHARACTER-SET TRANSPARENT implies SET TRANSFER TRANSLATION OFF.

    File scanning is also used in the TYPE command. The source file type and character set are determined as above, and then the file is automatically converted to your display character-set, line by line. In Kermit 95, the display character-set is Unicode, perhaps converted to your current console code page; in other versions of C-Kermit, it is your current file character-set. Thus if you have the following set appropriately:

      SET FILE CHARACTER-SET (necessary in Unix but not K95)
      SET FILE DEFAULT 7BIT CHARACTER-SET
      SET FILE DEFAULT 8BIT CHARACTER-SET
    

    then you should be able to TYPE any text file and see something reasonable. For example, in Unix, if your DEFAULT 7BIT-CHARACTER-SET is ITALIAN and your DEFAULT 8BIT-CHARACTER-SET is LATIN1, and your FILE CHARACTER-SET is LATIN1, you can TYPE an Italian ISO 646 file, a Latin-1 file, or any kind of Unicode file, and have it translated automatically to Latin-1 for your display.

    In the GUI version of Kermit 95, you can see mixtures of many different scripts if the file is UTF8 or UCS2: Roman, Cyrillic, Hebrew, Greek, Armenian, Georgian, etc, all on the same screen at once.

    File scanning also adds a new criterion for file selection, i.e. to select only text (or binary) files. Several commands now include a new switch, /TYPE:{BINARY,TEXT,ALL}. BINARY means select only binary regular files (not directories). TEXT means select only text files. ALL means don't scan; select all files. Examples:

    SEND /TYPE:BINARY *.*
    Sends only binary files, skipping over text files.

    NOTE: File scanning is NOT done when using external protocols (because the external protocol programs, such as sz, are processing each file, not Kermit).

    DIRECTORY /TYPE:TEXT
    Lists only text files but not binary files.

    DELETE /TYPE:BINARY foo.*
    Deletes all foo.* files that are regular binary files but does not delete any text files.

    CHMOD /TYPE:BINARY 775 *
    (UNIX) Changes the permissions of all binary files to 775.

    When FILE SCAN is OFF and FILE PATTERNS are ON, behavior is as before with PATTERNS ON, but with some improvements:

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    5. FILE AND DIRECTORY NAMES CONTAINING SPACES

    Prior to the introduction of the graphical user interface (GUI), it was inconceivable that file or directory names could contain spaces, because space is a field delimiter in all command languages. GUIs, however, use dialog boxes for filenames, so there is never any question of distinguishing a filename from adjacent fields -- because there are no adjacent fields -- and therefore it has become quite common on computers that have GUIs to have file and directory names composed of multiple words. Of course this poses problems for command shells and other text-oriented programs.

    Most command shells address these problems by allowing such names to be enclosed in doublequotes, e.g.:

      cd "c:\Program Files"
    

    C-Kermit previously used braces for this:

      cd {c:\Program Files}
    

    which was not what most people expected. And even when braces were used, Kermit had difficulties with completion, file menus, and so forth, within braced fields.

    C-Kermit 8.0 allows either doublequotes or braces to be used for grouping:

      send "this file"
      send {this file}
      rename "this file" "that file"
      rename {this file} "that file"
      rename "this file" {that file}
      cd {Program Files}
      cd "Program Files"
    

    Note that the doublequotes or brackets must enclose the whole file or directory specification:

      "c:\My Directory"
    

    not:

      c:\"My Directory"
    

    In C-Kermit 8.0, you can also use completion on these filenames, in which case Kermit supplies the quotes (or braces) automatically. Example (in which the current directory contains only one file whose name starts with "th" and its full name is "this file" (without the quotes, but with the space)):

      cat th<Tab>
    

    Kermit repaints the filename field like this:

      cat "this file"
    

    That is, it backspaces over the original "th" and then writes the filename in doublequotes.

    If completion is only partial, Kermit still supplies the quotes, but in this case also beeps. To continue the filename, you must first backspace over the closing quote. The closing quote is supplied in this case to make sure that you can see the spaces, especially if they are trailing. For example, if the current directory contains two files whose names start with "th", and their fill names are "this file" and "this other file":

      cat th<Tab>
    

    Kermit prints:

      cat "this "<Beep>
    

    If it didn't print the closing quote, you would probably wonder why it was beeping.

    Also, if you begin a filename field with a doublequote or opening brace, now you can use completion or get ?-help; this was never possible before.

     C-Kermit>type "thi? Input file specification, one of the following:
       this file        this other file
     C-Kermit>type "thi_
    

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    6. OTHER COMMAND PARSING IMPROVEMENTS

    6.1. Grouping Macro Arguments

    Doublequotes now can be used in macro invocations to group arguments containing spaces, where previously only braces could be used:

      define xx show args
      xx one "this is two" three
    

    Result:

      Macro arguments at level 0 (\v(argc) = 4):
       \%0 = xx
       \%1 = one
       \%2 = this is two
       \%3 = three
    

    Also, you can now quote braces and quotes in macro args (this didn't work before). Examples:

      xx "{"  ; The argument is a single left brace
      xx {"}  ; The argument is a doublequote character
    

    In case this new behavior interferes with your scripts, you can restore the previous behavior with:

      SET COMMAND DOUBLEQUOTING OFF
    

    6.2. Directory and File Name Completion

    C-Kermit 8.0 also includes better completion for directory names, e.g. in the CD command. If the name typed so far uniquely matches a directory name, it is completed (as before), but now if the directory contains any subdirectories, completion is partial (allowing you to supply additional path segments without backspacing); otherwise it is complete.

    Completion has also been improved for file and directory names that contain not only spaces (as described above) but also "metacharacters" such as asterisk (*) and tilde (~): now the field is repainted if necessary. For example, if the current directory contains only one file whose name contains "blah", then in:

      type *blah<Tab>
    

    "*blah" is replaced by the filename. In earlier releases, the part typed so far was left on the command line (and in the history buffer), so even when the original command worked, the recalled version would not. Similarly for ~ (the nearly-universal Unix notation for username):

      type ~olga/x<Tab>
    

    is repainted as (e.g.):

      type /users/home/olga/x(Beep)
    

    Speaking of command history, the new SHOW HISTORY command shows your command history and recall buffer. SAVE COMMAND HISTORY saves it into a file of your choice.

    6.3. Passing Arguments to Command Files

    The method for passing arguments to command files has been improved. Prior to C-Kermit 7.0 there was no provision for doing this. In C-Kermit 7.0, the TAKE command was changed to allow arguments to be given after the filename:

      take commandfile arg1 arg2 ...
    

    This was accomplished by replacing the current \%1, \%2, etc, with the given arguments, since a new set of macro argument variables is created only when a macro is executed, not a command file. It is much more intuitive, however, if arguments to command files worked like those to macros: the command file sees the arguments as its own \%1, \%2, etc, but the caller's variables are not disturbed. C-Kermit 8.0 accomplishes this by automatically creating an intermediate temporary macro to start the command file (if any arguments were given), thus creating a new level of arguments as expected.

    6.4. More-Prompting

    The familiar --more?-- prompt that appears at the end of each screenful of command-response output now accepts a new answer: G (Go) meaning "show all the rest without pausing and asking me any more questions". P (Proceed) is a synonym for G.

    6.5. Commas in Macro Definitions

    As noted in the C-Kermit manual, comma is used to separate commands in a macro definition. Even when the macro is defined on multiple lines using curly-brace block-structure notation without commas, the definition is still stored internally as a comma-separated list of commands. Therefore special tricks are needed to include a comma in a command. The classic example is:

      define foo {
          (some command)
          if fail echo Sorry, blah failed...
      }
    

    This would result in Kermit trying to execute a "blah" command. This could always be handled by enclosing the text in braces:

      define foo {
          (some command)
          if fail echo {Sorry, blah failed...}
      }
    

    but doublequotes (more intuitive) should have worked too. Now they do:

      define foo {
          (some command)
          if fail echo "Sorry, blah failed..."
      }
    

    6.6. Arrow Keys

    As of version 8.0.201, C-Kermit on most platforms lets you access the command history buffer with arrow keys, just as you always could with control characters. The restrictions are:

    1. Only Up and Down arrow keys are accepted.
    2. Only 7-bit ANSI arrow-key sequences are understood (ESC followed by [ or uppercase letter O, followed by uppercase letter A or (up) B (down).

    This change was made to facilitate command recall in Linux-based PDAs that don't have a Control key, or at least not one that's easily (or always) accessible, such as the Sharp Zaurus SL5500.

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    7. NEW COMMANDS AND SWITCHES

    See Section 4 for more about file scanning and the /TYPE: switch.

    ASK[Q] [ /TIMEOUT:number /QUIET /DEFAULT:text ] variable [ prompt ]
    The new optional /TIMEOUT: switch for ASK and ASKQ causes the command to time out and and fail if no response is given within the specified number of seconds, 1 or greater (0 or less means no timeout, wait forever). This works just like SET ASK-TIMER, except its effect is local to the ASK command with which it is given and it does not disturb the global ask timer setting. The new /QUIET switch tells Kermit not to print an error message if the ASK or ASKQ command times out waiting for a response.

    Version 8.0.211 adds the /DEFAULT:text switch for ASK-Class commands (ASK, ASKQ, and GETOK). This lets you supply a default answer in case the user supplies an empty answer or the /TIMEOUT: switch was included and the time limit expired without an answer. In both these cases, the command succeeds.

    CAT filename
    Equivalent to TYPE /NOPAGE.

    CDUP
    Changes Kermit's local working directory to the parent of the current one. Equivalent to "cd .." in UNIX or Windows, "cd [-]" in VMS, "cd ^" in AOS/VS, etc; in other words, it's a platform-independent way of moving one level up in a directory tree.

    CHMOD [ switches ] permission files
    UNIX only. Sets file permissions for one or more files or directories. The permission must be given as an octal number, e.g. 664, 755. Switches: /DIRECTORIES, /FILES, /NOLIST, /PAGE, /DOTFILES, /LIST, /NOPAGE, /RECURSIVE, /TYPE:{TEXT,BINARY,ALL}, /SIMULATE. The /TYPE: switch allows selection of only text or binary files. For example, if you have a mixture of source files and executables, you can use "chmod /files /type:text 664" to give owner/group read/write and world read permission to the text files, and "chmod /files /type:binary 775" to give the same plus execute permission to the executables. Use /SIMULATE to see which files would be affected, without actually changing their permissions.

    CLEAR KEYBOARD-BUFFER
    Flushes any as-yet unread characters from the keyboard input buffer. Useful for flushing typeahead in scripts.

    CONTINUE
    When given at an interactive command prompt that was reached by issuing a PROMPT command (described in this section) from a script, this command returns to the script, continuing its execution at the command after the PROMPT command. In this context, CONTINUE is simply a more-intuitive synonym for END.

    COPY, RENAME, and TRANSLATE
    These commands now work on file groups if the target filename is a directory, e.g. "copy oofa.* ..", "rename * ~olga/tmp/"

    COPY /APPEND source destination
    The source file specification can now include wildcards, in which case all of the source files that match will go into the destination file in alphabetical order by name.

    DELETE /ASK
    Asks permission to delete each file before deleting it. In C-Kermit 7.0, the answers were "yes" (or "ok") and "no". C-Kermit 8.0 adds "go" (meaning, delete all the rest without asking) and "quit" (cancel the DELETE command and return to the prompt).

    DELETE /DIRECTORIES
    Deletes not only files but also directories.

    DELETE /RECURSIVE
    Deletes all files that match the given file specification in the current (or given) directory and all directories beneath it.

    DELETE /SUMMARY
    Prints only the number of files deleted and total size freed, without listing each file.

    DELETE /TREE
    Shorthand for DELETE /RECURSIVE /DIRECTORIES /DOTFILES/. Equivalent to Windows DELTREE or Unix "rm -Rf". If no file specification is given, the contents of the current directory, plus all of its subdirectories and their contents, are deleted.

    DELETE /TYPE:BINARY
    Delete only regular binary files (requires FILE SCAN ON).

    DELETE /TYPE:TEXT
    Delete only regular text files (requires FILE SCAN ON).

    DIRECTORY [ switches ] [ filespec [ filespec [ filespec ... ] ] ]
    The DIRECTORY command now accepts more than one file specification; e.g. "directory moon.txt sun.doc stars.*".

    DIRECTORY /NORECURSIVE xxx
    If xxx is a directory name, forces listing of the directory itself rather than its contents.

    DIRECTORY /FOLLOWLINKS xxx
    (UNIX only) Tells the DIRECTORY command to follow symbolic links. This not the default because it can cause endless loops.

    DIRECTORY /NOFOLLOWLINKS xxx
    (UNIX only) Tells the DIRECTORY command not to follow symbolic links, but rather, merely to list them. This is the default.

    DIRECTORY /OUTPUT:filename
    Sends the results of the DIRECTORY command to the given file.

    DIRECTORY /SUMMARY
    Prints only the number of directories and files and the total size, without listing each file.

    DIRECTORY /TYPE:{TEXT,BINARY}
    Shows only files of the selected type, based on file scan.

    DIRECTORY /XFERMODE
    Now shows results of file scan (see Section 4).

    FOPEN [ switches ] channel filename
    As of version 8.0.211, FOPEN allows /dev/tty as a filename in Unix-based operating systems.

    FREAD /TRIM
    (8.0.211) Trims any trailing blanks or tabs from the item (such as a line of text) that it has read.

    FREAD /UNTABIFY
    (8.0.211) Converts Horizontal Tab characters to the appropriate number of spaces, based on VT100-like tab stops (1,9,17,25,...).

    GREP [ switches ] pattern files
    Similar to Unix grep command: displays file lines that match the given pattern. Switches:

    /COUNT[:variable]
    Don't show the matching lines, just tell how many lines match. If a variable name is specified, the count is stored in the given variable.
    /DOTFILES
    Include files whose names begin with dot.
    /LINENUMBERS
    Show line numbers of matching lines.
    /NAMEONLY
    only list the names of files that contain matching lines, but not the lines themselves.
    /NOBACKUP
    Skip backup files.
    /NOCASE
    Ignore alphabetic case while pattern matching.
    /NODOTFILES
    skip files whose names start with dot (period).
    /NOLIST
    Suppress output but set SUCCESS or FAILURE according to search result.
    /NOMATCH
    Look for lines that do not match the pattern.
    /NOPAGE
    Don't pause between screens of output.
    /OUTPUT:filename
    Write results into the given file.
    /PAGE
    Pause between screens of output.
    /RECURSIVE
    Search files in subdirectories too.
    /TYPE:{TEXT,BINARY}
    Search only files of the specified type.

    Synonyms: FIND, SEARCH.

    GETOK /TIMEOUT:n /QUIET /DEFAULT:text
    The new /QUIET switch instructs GETOK, when given a timeout, not to print an error message if it times out. As of 8.0.211, a default answer can be supplied (see ASK).

    HEAD [ switches ] filename
    Equivalent to TYPE /HEAD [ other-switches ] filename.

    HELP DATE
    Explains date-time formats, including timezone notation and delta times.

    HELP FIREWALLS
    Explains the firewall negotiation capabilities of your version of Kermit.

    KCD [ symbolic-directory-name ]
    Changes Kermit's working directory to the named symbolic directory, such as such as exedir, inidir, startup, download, or and home. Type "kcd ?" for a list of symbolic directory names known to your copy of Kermit, or give the new ORIENTATION command for a more detailed explanation. If you give a KCD command without a directory name, Kermit returns to its "home" directory, which is determined in some way that depends on the underlying operating system, but which you can redefine with the (new) SET CD HOME command. Your home directory is shown by SHOW CD and it's also the value of the \v(home) variable.

    LICENSE
    Displays the C-Kermit license.

    L-commands
    When Kermit has a connection to a Kermit or FTP server, file management commands such as CD, DIRECTORY, and DELETE might be intended for the local computer or the remote server. C-Kermit 8.0.200 and earlier always executes these commands on the local computer. If you want them executed by the remote server, you have to prefix them with REMOTE (e.g. REMOTE CD) or use special R-command aliases (e.g. RCD = REMOTE CD, RDIR = REMOTE DIR, etc). But this feels unnatural to FTP users, who expect unprefixed file management commands to be executed by the remote server, rather than locally. C-Kermit 8.0.201 adds automatic locus switching to present an FTP-like interface for FTP connections and the normal Kermit interface for Kermit connections, and a SET LOCUS command (described below) to control whether or how this is done. For when LOCUS is REMOTE, a new set of commands was added for local management: LCD (Local CD), LDIR (Local DIR), etc. These are described below under SET LOCUS.

    MORE filename
    Equivalent to TYPE /PAGE.

    ORIENTATION
    Displays symbolic directory names and the corresponding variable names and values. The symbolic names, such as exedir, inidir, startup, download, and home, can be used as arguments to the new KCD command.

    PROMPT [ text ]
    For use in a macro or command file: enters interactive command mode within the current context (Section 8.1). If the optional text is included, the prompt is set to it. The text can include variables, functions, etc, as in the SET PROMPT command. They are evaluated each time the prompt is printed. Unlike the SET PROMPT command, the text argument applies only to the current command level. Thus you can have different prompts at different levels.

    REMOTE SET MATCH { DOTFILE, FIFO } { ON, OFF }
    Allows the client to tell the server whether wildcards sent to the server should match dot files (files whose names begin with period) or FIFOs (named pipes). See SET MATCH.

    SET ATTRIBUTE RECORD-FORMAT { ON, OFF }
    Allows control of the Kermit's Record-Format attribute. Set this to OFF in case incoming file are refused due to unknown or invalid record formats if you want to accept the file anyway (and, perhaps, postprocess it to fix its record format).

    SET CD HOME [ directory ]
    Specifies the target directory for the CD and KCD commands, when they are given without an argument, and also sets the value of the \v(home) variable.

    SET EXIT HANGUP { OFF, ON }
    Normally ON, meaning that when Kermit exits, it also explicitly hangs up the current SET LINE / SET PORT serial port according to the current SET MODEM TYPE and SET MODEM HANGUP METHOD, and closes the port device if it was opened by Kermit in the first place (as opposed to inherited). SET EXIT HANGUP OFF tells Kermit not to do this. This can't prevent the operating system from closing the device when Kermit exits (and it's a "last close") but if the port or modem have been conditioned to somehow ignore the close and keep the connection open, at least Kermit itself won't do anything explicit to hang it up or close it.

    SET FILE EOF { CTRL-Z, LENGTH }
    Specifies the end-of-file detection method to be used by C-Kermit when sending and receiving text files, and in the TYPE and similar text-file oriented commands. The normal and default method is LENGTH. You can specify CTRL-Z when handling CP/M or MS-DOS format text files, in which a Ctrl-Z (ASCII 26) character within the file marks the end of the file.

    SET FILE LISTSIZE number
    Allocates space for the given number of filenames to be filled in by the wildcard expander. The current number is shown by SHOW FILE. If you give a command that includes a filename containing a wildcard (such as "*") that matches more files that Kermit's list has room for, you can adjust the list size with this command.

    SET FILE STRINGSPACE number
    Allocates space for the given amount of filename strings for use by the wildcard expander. The current number is shown by SHOW FILE. The number is the total number of bytes of all the file specifications that match the given wildcard.

    If you need to process a bigger list of files than your computer has memory for, you might be able use an external file list. The Kermit SEND and the FTP PUT and GET commands accept a /LISTFILE: switch, which gives the name of a file that contains the list of files to be transferred. Example for UNIX:

      !find . -print | grep / > /tmp/names
      ftp put /update /recursive /listfile:/tmp/names
    

    SET LOCUS { AUTO, LOCAL, REMOTE }
    Added in C-Kermit 8.0.201.   Sets the locus for unprefixed file management commands such as CD, DIRECTORY, MKDIR, etc. When LOCUS is LOCAL these commands act locally and a REMOTE (or R) prefix (e.g. REMOTE CD, RCD, RDIR) is required to send file management commands to a remote server. When LOCUS is REMOTE, an L prefix is required to issue local file management commands (e.g. LCD, LDIR). The word LOCAL can't be used as a prefix since it is already used for declaring local variables. LOCUS applies to all types of connections, and thus is orthogonal to SET GET-PUT-REMOTE, which selects between Kermit and FTP for remote file-transfer and management commands. The default LOCUS is AUTO, which means we switch to REMOTE whenever an FTP connection is made, and to LOCAL whenever a non-FTP connection is made, and switch back accordingly whenever a connection is closed. So by default, Kermit behaves in its traditional manner unless you make an FTP connection, in which case it acts like a regular FTP client (but better :-)   LOCUS applies to the following commands:

      Unprefixed    Remote       Local        Description        
       CD (CWD)      RCD          LCD          Change (Working) Directory
       CDUP          RCDUP        LCDUP        CD Up
       PWD           RPWD         LPWD         Print Working Directory
       DIRECTORY     RDIR         LDIR         Request a directory listing
       DELETE        RDEL         LDEL         Delete (a) file(s)
       RENAME        RREN         LREN         Rename a file
       MKDIR         RMKDIR       LMKDIR       Create a directory
       RMDIR         RRMDIR       LRMDIR       Remove a directory
    

    SET MATCH { DOTFILE, FIFO } { ON, OFF }
    Whether C-Kermit filename patterns (wildcards) should match filenames that start with dot (period), or (Unix only) FIFOs (named pipes). The defaults are to skip dotfiles in Unix but match them elsewhere, and to skip FIFOs. Applies to both interactive use and to server mode, when the server receives wildcards, e.g. in a GET command. Also see REMOTE SET MATCH.

    SET OPTIONS DIRECTORY /DOTFILES
    Now works for server listings too (UNIX only). Give this command prior to having Kermit enter server mode, and then it will show files whose names begin with dot (period) when sent a REMOTE DIRECTORY command.

    SET QUIET ON
    (as well as the -q command-line option) Now applies also to:
    • SET HOST connection progress messages.
    • "Press the X or E key to cancel" file-transfer message.
    • REMOTE CD response.
    • REMOTE LOGIN response.

    SET RECEIVE PERMISSIONS { ON, OFF }
    Tells C-Kermit whether to set the permissions of incoming files (received with Kermit protocol) from the permissions supplied in the file's Attribute packet (if any). Normally ON. Also see SET SEND PERMISSIONS.

    SET ROOT directory
    Like UNIX chroot, without requiring privilege. Sets the root for file access, does not allow reference to or creation of files outside the root, and can't be undone.

    SET SEND PERMISSIONS { ON, OFF }
    Tells C-Kermit whether to include file permissions in the attributes it includes with each file when sending with Kermit protocol. Also see SET RECEIVE PERMISSIONS.

    SET TCP { HTTP-PROXY, SOCKS-SERVER } /USER:name /PASSWORD:text
    These commands now allow specification of username and password.

    SET TERMINAL . . .
    (See Section 12.)

    SET TRANSFER MESSAGE [ text ]
    Sets an initial text message to be displayed in the file-transfer display. The transfer message is automatically deleted once used, so must be set each time a message a desired. Any variables in the message are evaluated at the time the SET command is given. If the optional text is omitted, any transfer message that is currently set is removed. Synonym: SET XFER MSG. SHOW TRANSFER displays it if it has been set but not yet used.

    SHOW COMMUNICATIONS
    In C-Kermit 8.0, SHOW COMMUNICATIONS, when given in remote mode (i.e. before any connection has been established), tells the typical dialout device name for the particular platform on which it's running (e.g. TXA0: for VMS, or /dev/cua0p0 for HP-UX). On Unix platforms, it also tells the name of the lockfile directory. This way, you have an idea of what the SET LINE device name should look like, and if the SET LINE command fails, you know the name of the directory or device that is protected against you.

    SHOW VARIABLES [ name [ name [ ... ] ] ]
    In C-Kermit 8.0.201 you can request values of a list of built-in (\v(xxx)) variables. Each name is a pattern, as before, but now it a free pattern rather than an anchored one (explained in Section 8.12) so now "show var date time" shows the values of all variables whose names include the strings "date" or "time".

    TAIL [ switches ] filename
    Equivalent to TYPE /TAIL [ other-switches ] filename.

    TRANSMIT /NOECHO [ other switches ] filename
    The /NOECHO switch is equivalent to giving the command SET TRANSMIT ECHO OFF prior to the TRANSMIT command, except the switch affects only the command with which it was given and does not affect the prevailing global setting.

    TRANSMIT /NOWAIT [ other switches ] filename
    The /NOWAIT switch is equivalent to giving the command SET TRANSMIT PROMPT 0 prior to the TRANSMIT command, except the switch affects only the command with which it was given and does not affect the prevailing global setting.

    TRANSMIT /NOWAIT /NOECHO /BINARY [ other switches ] filename
    When the TRANSMIT command is given with the /NOWAIT, /NOECHO, and /BINARY switches, this activates a special "blast the whole file out the communications connection all at once" mode that Kermit didn't have prior to version 8.0. There has been increasing demand for this type of transmission with the advent of devices that expect image (e.g. .JPG) or sound (e.g. .MP3) files as raw input. The obvious question is: how does the receiving device know when it has the whole file? This depends on the device, of course; usually after a certain amount of time elapses with nothing arriving, or else when Kermit hangs up or closes the connection.

    TYPE /CHARACTER-SET:name
    Allows you to specify the character set in which the file to be typed is encoded.

    TYPE /NUMBER
    Adds line numbers.

    TYPE /OUTPUT:filename
    Sends the results of the TYPE command to the given file.

    TYPE /TRANSLATE-TO:name
    Used in conjunction with TYPE /CHARACTER-SET:xxx; allows you to specify the character set in which the file is to be displayed.

    TYPE /TRANSPARENT
    Used to disable character-set translation in the TYPE command, which otherwise can take place automatically based on file scanning, even when /CHARACTER-SET and /TRANSLATE-TO switches are not given.

    VOID text
    Parses the text, evaluating any backslash items in it (such as function calls) but doesn't do anything further, except possibly printing error messages. Useful for invoking functions that have side effects without using or printing their direct results, e.g. "void \fsplit(\%a,&a)".

    Symbolic Links in UNIX

    The UNIX versions of C-Kermit have had /FOLLOWLINKS and /NOFOLLOWLINKS switches added to several commands to control the treatment of symbolic links. Different commands deal differently with symbolic links:

    Kermit SEND, FTP MPUT
    /NOFOLLOWLINKS is the default, which means symbolic links are skipped entirely. The alternative, /FOLLOWLINKS, should be used with caution, since an innocent link might point to a whole file system, or it might cause a loop. There is no way in Kermit or FTP protocol to send the link itself. We either skip them or follow them; we can't duplicate them.

    DIRECTORY
    /NOFOLLOWLINKS is the default, which means the DIRECTORY command lists symbolic links in a way that shows they are links, but it does not follow them. The alternative, /FOLLOWLINKS, follows links and gives information about the linked-to directories and files.

    DELETE, RMDIR
    The DELETE command does not have link-specific switches. DELETE never follows links. If you tell Kermit to delete a symbolic link, it deletes the link itself, not the linked-to file. Ditto for RMDIR.

    COPY
    The COPY command behaves just like the UNIX cp command; it always follows links.

    RENAME
    The RENAME command behaves just like the UNIX mv command; it operates on links directly rather than following.

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    8. OTHER SCRIPTING IMPROVEMENTS

    8.1. Performance and Debugging

    A command cache for frequently used commands plus some related optimizations increases the speed of compute-bound scripts by anywhere from 50% to 1000%.

    The new PROMPT command can be used to set breakpoints for debugging scripts. If executed in a command file or macro, it gives you an interactive command prompt in the current context of the script, with all its variables, arguments, command stack, etc, available for examination or change, and the ability to resume the script at any point (END resumes it, Ctrl-C or STOP cancels it and returns to top level).

    The new Ctrl-C trapping feature (Section 8.14) lets you intercept interruption of scripts. This can be used in combination with the PROMPT command to debug scripts. Example:

    define ON_CTRLC {
        echo INTERRUPTED BY CTRL-C...
        echo The command stack has not yet been rolled back:
        show stack
        echo Type Ctrl-C again or use the END command to return to top level.
        prompt Debug>
    }
    

    Adding this ON_CTRL definition to your script lets you interrupt it at any point and get prompt that is issued at the current command level, so you can query local variables, etc.

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    8.2. Using Macros as Numeric Variables

    A macro is a way to assign a value to a name, and then use the name to refer to the value. Macros are used in two ways in Kermit: as "subroutines" or functions composed of Kermit commands, which are executed, or as variables to hold arbitrary values -- text, numbers, filenames, etc.

    When a macro is to be executed, its name is given as if it were a C-Kermit command, optionally preceded by the word "do". When a macro is used as a variable, it must be "escaped" with \m(xxx) (or equivalent function, e.g. \s(xxx), \:(xxx), \fdefinition(xxx)), where xxx is the macro name, for example:

      define filename /usr/olga/oofa.txt
      send \m(filename)
    

    Of course variables can also hold numbers:

      define size 17
      declare \&a[\m(size)]
      ...
      define index 3
      if ( == \m(index) 3 ) echo The third value is: \&a[\m(index)]
      evaluate index (\m(index) * 4)
      if ( > \m(index) \m(size) ) echo Out of range!
    

    But these are contexts in which only numbers are valid. C-Kermit 8.0 has been changed to treat non-escaped non-numeric items in strictly numeric contexts as macro names. So it is now possible (but not required) to omit the \m(...) notation and just use the macro name in these contexts:

      define size 17
      declare \&a[size]
      ...
      define index 3
      if ( == index 3 ) echo The third value is: \&a[index]
      evaluate index (index * 4)
      if ( > index size ) echo Out of range!
    

    This is especially nice for loops that deal with arrays. Here, for example, is a loop that reverses the order of the elements in an array. Whereas formerly it was necessary to write:

      .\%n ::= \fdim(&a)
      for \%i 1 \%n/2 1 {
          .tmp := \&a[\%n-\%i+1]
          .\&a[\%n-\%i+1] := \&a[\%i]
          .\&a[\%i] := \m(tmp)
      }
    

    Recoding this to use macro names "i" and "n" instead of the backslash variables \%i and \%n, we have:

      .n ::= \fdim(&a)
      for i 1 n/2 1 {
          .tmp := \&a[n-i+1]
          .\&a[n-i+1] := \&a[i]
          .\&a[i] := \m(tmp)
      }
    

    which reduces the backslash count to less than half. The final statement in the loop could be written ".\&a[i] ::= tmp" if the array contained only numbers (since ::= indicates arithmetic expression evaluation).

    Also, now you can use floating-point numbers in integer contexts (such as array subscripts), in which case they are truncated to an integer value (i.e. the fractional part is discarded).

    Examples of numeric contexts include:

    and:

    Macro names used in numeric contexts must not include mathematical operators. Although it is legal to create a macro called "foo+bar", in a numeric context this would be taken as the sum of the values of "foo" and "bar". Any such conflict can be avoided, of course, by enclosing the macro name in \m(...).

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    8.3. New IF Conditions

    Several new IF conditions are available:

    IF DECLARED arrayname
    Explained in Section 8.6.

    IF KBHIT
    Allows a script to test whether a key was pressed without actually trying to read it.

    IF KERBANG (Unix only)
    True if Kermit was started from a Kerbang script. This is useful for knowing how to interpret the \&@[] and \&_[] argument vector arrays, and under what conditions to exit.

    IF INTEGER n
    This is just a synonym for IF NUMERIC, which is true if n contains only digits (or, if n is a variable, its value contains only digits).

    By contrast, IF FLOAT n succeeds if n is a floating-point number OR an integer (or a variable with floating-point or integer value). Therefore, IF FLOAT should be used whenever any kind of number is acceptable, whereas IF INTEGER (or IF NUMERIC) when only an integer can be used.

    [ Top ] [ Contents ] [ C-Kermit Home ] [ Kermit Home ]

    8.4. The ON_UNKNOWN_COMMAND Macro

    The new ON_UNKNOWN_COMMAND macro, if defined, is executed whenever you give a command that is not known to C-Kermit; any operands are passed as arguments. Here are some sample definitions:

      DEF ON_UNKNOWN_COMMAND telnet \%1 ; Treat unknown commands as hostnames
      DEF ON_UNKNOWN_COMMAND dial \%1   ; Treat unknown commands phone numbers
      DEF ON_UNKNOWN_COMMAND take \%1   ; Treat unknown commands as filenames
      DEF ON_UNKNOWN_COMMAND !\%*       ; Treat unknown commands as shell commands
    

    The ON_CD macro, if defined, is executed whenever Kermit is given a CD (change directory) command (8.0.211). Upon entry to this macro, the directory has already changed and the new directory string is available in the \v(directory) variable, and also as the first argument (\%1).

    [ Top ] [ Contents ] [ C-Kermit Home ] [ Kermit Home ]

    8.5. The SHOW MACRO Command

    The SHOW MACRO command has been changed to accept more than one macro name:

      (setq a 1 b 2 c 3)
      show mac a b c
      a = 1
      b = 2
      c = 3
    

    An exact match is required for each name (except that case doesn't matter). If you include wildcard characters, however, a pattern match is performed:

      show mac [a-c]*x
    

    shows all macros whose names start with a, b, or c, and end with x.

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    8.6. Arrays

    A clarification regarding references to array names (as opposed to array elements): You can use array-name "abbreviations" like &a only in contexts that expect array names, like ARRAY commands or array-name function arguments such as the second argument of \fsplit(). In a LOCAL statement, however, you have to write \&a[], since "local &a" might refer to a macro named "&a".

    In function arguments, however, you MUST use the abbreviated form: \fsplit(\%a,&a) or \fsplit(\%a,&a[]). If you include the backslash (as in "\fsplit(\%a,\&a[])") a parse error occurs.

    Here are the new array-related commands:

    IF DECLARED arrayname
    Allows a script to test whether an array has been declared. The arrayname can be a non-array backslash variable such as \%1 or \m(name), in which case it is evaluated first, and the result is treated as the array name. Otherwise, arrayname is treated as in the ARRAY commands: it can be a, &a, &a[], \&a, \&a[], \&a[3], \&a[3:9], etc, with the appropriate results in each case. Synonym: IF DCL.

    UNDECLARE arrayname
    UNDECLARE is a new top-level command to undeclare an array. Previously this could only be done with "declare \&a[0]" (i.e. re-declare the array with a dimension of 0).

    ARRAY LINK linkname arrayname
    Creates a symbolic link from the array named by linkname (which must be the name of an array that is not yet declared in the current context) to the array named by arrayname (which must the name of a currently declared array that is not itself a link, or a variable containing the name of such an array). The two names indicate the same array: if you change an array element, the change is reflected in the link too, and vice versa. If you undeclare the link, the real array is unaffected. If you undeclare the real array, all links to it disappear. If you resize an array (directly or through a link), all links to it are updated automatically.

    Array links let you pass array names as arguments to macros. For example, suppose you had a program that needed to uppercase all the elements of different arrays at different times. You could write a macro to do this, with the array name as an argument. But without array links, there would be no way to refer to the argument array within the macro. Array links make it easy:

      define arrayupper {
          local \&e[] \%i
          array link \&e[] \%1
          for i 1 \fdim(&e) 1 { .\&e[i] := \fupper(\&e[i]) }
      }
      declare \&a[] = these are some words
      arrayupper &a
      show array &a
    

    The macro declares the array link LOCAL, which means it doesn't conflict with any array of the same name that might exist outside the macro, and that the link is destroyed automatically when the macro exits. This works, by the way, even if the link name and the macro argument name are the same, as long as the link is declared LOCAL.

    As noted, you can't make a link to a nonexistent array. So when writing a macro whose job is to create an array whose name is passed as an argument, you must declare the array first (the size doesn't matter as long as it's greater than 0). Example:

      define tryme {                ; Demonstration macro
          local \&e[]               ; We only need this inside the macro
          array link \&e[] \%1      ; Make local link
          shift                     ; Shift argument list
          void \fsplit(\%*,&e)      ; Split remainder of arg list into array
      }
      declare \&a[1]                ; Declare target array in advance
      tryme &a here are some words  ; Invoke the macro with array name and words
      show array a                  ; See the results
    

    One final improvement allows the macro itself to declare the array (this was not possible in earlier Kermit releases): if the array name in the DECLARE command is a variable (and not an array name), or includes variables, the resulting value is used as the array name. So:

      define tryme {                ; Demonstration macro
          declare \%1[1]            ; Preliminary declaration for target array
          local \&e[]               ; We only need this inside the macro
          array link \&e[] \%1      ; Make local link
          shift                     ; Shift argument list
          void \fsplit(\%*,&e)      ; Split remainder of arg list into array
      }
      tryme &a here are some words  ; Invoke the macro with array name and words
      show array a                  ; See the results
    

    The SHOW ARRAY command now indicates whether an array name is a link.

    Also see the descriptions of \fjoin() and \fsplit(), plus Section 8.10 on the MINPUT command, which shows how an entire array (or segment of it) can be used as the MINPUT target list.

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    8.7. New or Improved Built-in Variables and Functions

    The following new built-in variables are available:

      \v(buildid)       A date string like "20000808" indicating when C-Kermit was built.
      \v(ftime)         Current time, secs since midnight, including fraction of second.
      \v(iprompt)       The current SET PROMPT value
      \v(sexp)          The most recent S-Expression (see Section 9)
      \v(sdepth)        The current S-Expression invocation depth (Section 9)
      \v(svalue)        The value of the most recent S-Expression (Section 9)
    

    \v(ftp_code) Most recent FTP response code (Section 3) \v(ftp_connected) FTP connection status (Section 3) \v(ftp_cpl) FTP Command Protection Level (Section 3.2) \v(ftp_dpl) FTP Data Protection Level (Section 3.2) \v(ftp_getputremote) The current SET GET-PUT-REMOTE setting (Section 3.8) \v(ftp_host) Name or IP address of FTP server (Section 3) \v(ftp_loggedin) FTP login status (Section 3) \v(ftp_message) Most recent FTP response message (Section 3) \v(ftp_security) FTP Security method (Section 3.2) \v(ftp_server) OS type of FTP server (Section 3)

    \v(http_code) Most recent HTTP response code \v(http_connected) HTTP connection status \v(http_host) Name or IP address of HTTP server \v(http_message) Most recent HTTP response message \v(http_security) TLS cipher used to secure the HTTP session

    \v(hour) Hour of the day, 0 to 23. \v(timestamp) Equivalent to "\v(ndate) \v(time)". \v(log_debug) Current debug log file, if any. \v(log_packet) Current packet log file, if any. \v(log_session) Current session log file, if any. \v(log_transaction) Current transaction log file, if any. \v(log_connection) Current connection log file, if any.

    The following new or improved built-in functions are available:

      \fcmdstack()            Allows programmatic access to the command stack.
      \fcvtdate()             Section 8.13, format options added
      \fdelta2secs()          Section 8.13
      \fdostounixpath(s1)     Converts a DOS filename to Unix format.
      \fsplit()               Now allows grouping/nesting in source string.
      \fword()                Allows the same grouping and nesting.
      \fjoin(&a,s1,n1,n2)     Copies an array into a single string.
      \fsubstitute(s1,s2,s3)  Substitutes characters within a string.
      \freplace()             Has new 4th "occurrence" argument.
      \fsexpression()         Evaluates an S-Expression (explained in Section 9).
      \ftrim(), \fltrim()     Now trim CR and LF by default, as well as SP and Tab.
      \funixtodospath(s1)     Converts a Unix filename to DOS format.
      \fkeywordval(s1,c1)     Assigns values to keywords (macros) (explained below).
    

    Most functions that have "2" in their names to stand for the word "to" can now also be written with "to", e.g. "\fdelta2secs()," \fdeltatosecs()."

    \funtabify(string)
    (New to 8.0.211) Replaces Horizontal Tab characters in the given string with spaces based on VT100-like tab stops.

    \fverify(s1,s2,n)
    As of version 8.0.211, returns -1 if s2 is an empty string. Previously it returned 0, making \fverify(abc,\%a) look as if \%a was a string composed of a's, b's, and/or c's when in fact it contained nothing.

    \fcode(string)
    As of version 8.0.211, returns 0 if string is empty or missing. Previously it returned the empty string, which made it unsafe to use in arithmetic or boolean expressions.

    \v(inscale)
    New to version 8.0.211, its value is the INPUT SCALE-FACTOR (Section 8.10), default 1.0.

    8.7.1. The \fkeywordval() Function

    \fkeywordval(s1,c1) is new to C-Kermit 8.0. Given a string s1 of the form "name=value", it creates a macro with the given name and assigns it the given value. If no value appears after the equal sign, any existing macro of the given name is undefined. Blanks are automatically trimmed from around the name and value. The optional c1 parameter is the assignment operator character, equal sign (=) by default. This function is handy for processing keyword parameters or any other form of parameter-value pair. Suppose, for example, you want to write a macro that accepts keyword parameters rather than positional ones:

      define MYDIAL {
          local \%i modem hangup method device speed number
          def number 5551234          ; Assign default parameter values
          def speed 57600
          def modem usrobotics
          def hangup rs232
          def method tone
          def country 1
          for \%i 1 \v(argc)-1 1 {    ; Parse any keyword parameters...
    	  if not \fkeywordval(\&_[\%i]) end 1 Bad parameter: "\&_[\%i]"
          }
          set dial country \m(country)
          set modem type \m(modem)
          set modem hang \m(hangup)
          set dial method \m(tone)
          set line \m(device)
          if fail stop 1
          set speed \m(speed)
          if fail stop 1
          show comm
          set dial display on
          dial \m(number)
          if success connect
      }
    

    In this example, all the defaults are set up inside the macro, and therefore it can be invoked with no parameters at all. But if you want to have the macro dial a different number, you can supply it as follows:

      mydial number=7654321
    

    You can supply any number of keyword parameters, and you can give them in any order:

      mydial number=7654321 hangup=modem speed=115200
    

    8.7.2. The \fsplit(), \fjoin(), and \fword() Functions

    \fjoin(&a,s1,n1,n2) is also new; it creates a string from an array (or a piece of one). &a is the name of the array (a range specifier can be included); s1 is a character or string to separate each element in the result string (can be omitted, in which case the elements are not separated at all), and n1 is a grouping mask, explained below. If s1 is empty or not specified, the array elements are separated with spaces. If you want the elements concatenated with no separator, include a nonzero n2 argument. Given the array:

      declare \&a[] = 0 1 2 3 4 5 6 7 8 9
    

    you can get effects like this:

      \fjoin(&a)      0 1 2 3 4 5 6 7 8 9
      \fjoin(&a,:)    0:1:2:3:4:5:6:7:8:9
      \fjoin(&a,{,})  0,1,2,3,4,5,6,7,8,9
      \fjoin(&a,...)  0...1...2...3...4...5...6...7...8...9
      \fjoin(&a,,,1)  0123456789
    

    \fsplit(), \fword(), \fstripb(), and \fjoin() accept a "grouping mask" argument, n1, which is a number from 0 to 63, in which:

       1 = "" doublequotes
       2 = {} braces
       4 = '' singlequotes
       8 = () parentheses
      16 = [] square brackets
      32 = <> angle brackets
    

    These can be OR'd (added) together to make any number 0-63 (-1 is treated the same as 63, 0 means no grouping). If a bit is on, the corresponding kind of grouping is selected. (If more than 1 bit is set for \fjoin(), only the lowest-order one is used.)

    If you include the same character in the grouping mask and the include list, the grouping mask takes precedence. Example:

      def \%a  a "b c d" e
      \fsplit(\%a,&a[],,,-1)  = 3  <-- doublequote used for grouping
      \fsplit(\%a,&a[],,",-1) = 3  <-- doublequote still used for grouping
    

    Nesting of matched left and right grouping characters (parentheses, braces, and brackets, but not quotes) is recognized. Example:

      def \%a a (b c <d e [f g {h i} j k] l m> n o) p
      \fsplit(\%a,&a,,,0)  = 16 (no grouping)
      \fsplit(\%a,&a,,,2)  = 15 (braces only)
      \fsplit(\%a,&a,,,16) = 11 (square brackets only)
      \fsplit(\%a,&a,,,32) =  7 (angle brackets only)
      \fsplit(\%a,&a,,,63) =  3 (all)
      \fsplit(\%a,&a,,,-1) =  3 (all)
    

    \fsplit() and \fjoin() are "reciprocal" functions. You can split a string up into an array and join it back into a new string that is equivalent, as long as \fsplit() and \fjoin() are given equivalent grouping masks, except that the type of braces might change. Example:

      def \%a a {b c [d e] f g} "h i" j <k l> m
      echo STRING=[\%a]
      echo WORDS=\fsplit(\%a,&a,,,-1)
      show array a
      asg \%b \fjoin(&a,{ },2)
      echo JOIN  =[\%b]
      echo WORDS=\fsplit(\%b,&b,,,-1)
      show array b
    

    The arrays a and b are identical. The strings a and b are as follows:

      \%a: a {b c [d e] f g} "h i" j <k l> m
      \%b: a {b c [d e] f g} {h i} j {k l} m
    

    It is possible to quote separator grouping characters with backslash to override their grouping function. And of course to include backslash itself in the string, it must be quoted too. Furthermore, each backslash must be doubled, so the command parser will still pass one backslash to \fsplit() for each two that it sees. Here are some examples using \fsplit() with a grouping mask of 8 (treat parentheses as grouping characters).

      String                  Result
        a b c d e f             6
        a b\\ c d e f           5
        a b (c d e) f           4
        a b \\(c d e\\) f       6
        a b \\\\(c d e\\\\) f   7
    

    \fsplit() has also been changed to create its array (if one is given) each time it is called, so now it can be conveniently called in a loop without having to redeclare the array each time.

    Incidentally... Sometimes you might want to invoke \fsplit() in a situation where you don't care about its return value, e.g. when you just want to fill the array. Now you can "call" \fsplit() or any other function with the new VOID command:

      void \fsplit(\%a,&a)
    

    \fsplit() and \fjoin() also accept a new, optional 6th argument, an options flag, a number that can specify a number of options. So far there is just one option, whose value is 1:

    separator-flag
    Normally separators are collapsed. So, for example,

      \fword(Three        little          words,2)
    

    returns "little" (the second word). Space is a separator, but there are multiple spaces between each word. If the value 1 is included in the option flag, however, each separator counts. If two separators are adjacent, an empty word is produced between them. This is useful for parsing (e.g.) comma-separated lists exported from databases or spreadsheets.

    8.7.3. The \fcmdstack() Function

    The new \fcmdstack() function gives access to the command stack:
    \fcmdstack(n1,n2)
    Arguments: n1 is the command stack level. If omitted, the current level, \v(cmdlevel), is used. n2 is a function code specifying the desired type of information:
      0 (default) = name of object at level n1.
      1 (nonzero) = object type (0 = prompt; 1 = command file; 2 = macro).
    
    The default for n2 is 0.

    The name associated with prompt is "(prompt)". Here's a loop that can be included in a macro or command file to show the stack (similar to what the SHOW STACK command does):

      for \%i \v(cmdlevel) 0 -1 {
          echo \%i. [\fcmdstack(\%i,1)] \fcmdstack(\%i,0)
      }
    

    In this connection, note that \v(cmdfile) always indicates the most recently invoked active command file (if any), even if that file is executing a macro. Similarly, \v(macro) indicates the most recently invoked macro (if any), even if the current command source is not a macro. The name of the "caller" of the currently executing object (command file or macro) is:

      \fcmdstack(\v(cmdlevel)-1)
    

    and its type is:

      \fcmdstack(\v(cmdlevel)-1,1)
    

    To find the name of the macro that invoked the currently executing object, even if one or more intermediate command files (or prompting levels) are involved, use a loop like this:

      for \%i \v(cmdlevel)-1 0 -1 {
          if = \fcmdstack(\%i,1) 2 echo CALLER = \fcmdstack(\%i,0)
      }
    

    Of course if you make a macro to do this, the macro must account for its own additional level:

      define CALLER {
          for \%i \v(cmdlevel)-2 0 -1 {
              if = \fcmdstack(\%i,1) 2 return \fcmdstack(\%i,0)
          }
          return "(none)"
      }
    

    The built-in variable \v(cmdsource) gives the current command source as a word ("prompt", "file", or "macro").

    8.7.4. The VOID Command

    VOID is like ECHO in that all functions and variables in its argument text are evaluated. but it doesn't print anything (except possibly an error message if a function was invocation contained or resulted in any errors). VOID sets FAILURE if it encounters any errors, SUCCESS otherwise.

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    8.8. The RETURN and END Commands

    The execution of a macro is terminated in any of the following ways:

    The same considerations apply to command files invoked by the TAKE command.

    If a macro does not execute any commands that set success or failure, then invoking the macro does not change the current SUCCESS/FAILURE status. It follows, then, that the mere invocation of a macro does not change the SUCCESS/FAILURE status either. This makes it possible to write macros to react to the status of other commands (or macros), for example:

      define CHKLINE {
          if success end 0
          stop 1 SET LINE failed - please try another device.
      }
      set modem type usrobotics
      set line /dev/cua0
      chkline
      set speed 57600
      dial 7654321
    

    By the way, none of this is news. But it was not explicitly documented before, and C-Kermit 7.0 and earlier did not always handle the RETURN statement as it should have.

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    8.9. UNDEFINing Groups of Variables

    The UNDEFINE command, which previously accepted one variable name, now accepts a list of them, and also accepts wildcard notation to allow deletion of variables that match a given pattern.

    UNDEFINE [ switches ] name [ name [ name [ ... ] ] ]
    Undefines the variables whose names are given. Up to 64 names may be given in one UNDEFINE command.

    If you omit the switches and include only one name, the UNDEFINE command works as before.

    Switches include:

    /MATCHING
    Specifies that the names given are to treated as patterns rather than literal variable names. Note: pattern matching can't be used with array references; use the ARRAY command to manipulate arrays and subarrays.

    /LIST
    List the name of each variable to be undefined, and whether it was undefined successfully ("ok" or "error"), plus a summary count at the end.

    /SIMULATE
    List the names of the variables that would be deleted without actually deleting them. Implies /LIST.

    The UNDEFINE command fails if there were any errors and succeeds otherwise.

    The new _UNDEFINE command is like UNDEFINE, except the names are assumed to be variable names themselves, which contain the names (or parts of them) of the variables to be undefined. For example, if you have the following definitions:

      define \%a foo
      define foo This is some text
    

    then:

      undef \%a
    

    undefines the variable \%a, but:

      _undef \%a
    

    undefines the macro foo.

    Normal Kermit patterns are used for matching; metacharacters include asterisk, question mark, braces, and square brackets. Thus, when using the /MATCHING switch, if the names of the macros you want to undefine contain any of these characters, you must quote them with backslash to force them to be taken literally. Also note that \%* is not the name of a variable; it is a special notation used within a macro for "all my arguments". The command "undef /match \%*" deletes all \%x variables, where x is 0..9 and a..z. Use "undef /match \%[0-9]" to delete macro argument variables or "undef /match \%[i-n]" to delete a range of \%x variables.

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    8.10. The INPUT and MINPUT Commands

    As of C-Kermit 8.0.211, the INPUT and MINPUT commands accept a switch:

    [M]INPUT /NOMATCH timeout
    The /NOMATCH switch allows INPUT or MINPUT to read incoming material for the specified amount of time, without attempting to match it with any text or patterns. When this switch is included, the [M]INPUT command succeeds when the timeout interval expires, with \v(instatus) set to 1, meaning "timed out", or fails upon interruption or i/o error.

    Also in version 8.0.211, there is a new way to apply a scale factor to [M]INPUT timeouts:

    SET INPUT SCALE-FACTOR floating-point-number
    This scales all [M]INPUT timeouts by the given factor, allowing time-sensitive scripts to be adjusted to changing conditions such as congested networks or different-speed modems without having to change each INPUT-class command. This affects only those timeouts that are given in seconds, not as wall-clock times. Although the scale factor can have a fractional part, the INPUT timeout is still an integer. The new built-in variable \v(inscale) tells the current INPUT SCALE-FACTOR.

    The MINPUT command can be used to search the incoming data stream for several targets simultaneously. For example:

      MINPUT 8 one two three
    

    waits up to 8 seconds for one of the words "one", "two", or "three" to arrive. Words can be grouped to indicate targets that contain spaces:

      MINPUT 8 nineteen twenty "twenty one"
    

    And of course you can also use variables in place of (or as part of) the target names:

      MINPUT 8 \%a \&x[3] \m(foo)
    

    Until now you had to know the number of targets in advance when writing the MINPUT statement. Each of the examples above has exactly three targets.

    But suppose your script needs to look for a variable number of targets. For this you can use arrays and \fjoin(), described in Section 8.7. Any number of \fjoin() invocations can be included in the MINPUT target list, and each one is expanded into the appropriate number of separate targets each time the MINPUT command is executed. Example:

      declare \&a[10] = one two three
      minput 10 foo \fjoin(&a) bar
    

    This declares an array of ten elements, and assigns values to the first three of them. The MINPUT command looks for these three (as well as the words "foo" and "bar"). Later, if you assign additional elements to the array, the same MINPUT command also looks for the new elements.

    If an array element contains spaces, each word becomes a separate target. To create one target per array element, use \fjoin()'s grouping feature:

      dcl \&a[] = {aaa bbb} {ccc ddd} {xxx yyy zzz}
    
      minput 10 \fjoin(&a)     <-- 7 targets
      minput 10 \fjoin(&a,,2)  <-- 3 targets
    

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    8.11. Learned Scripts

    C-Kermit now includes a simple script recorder that monitors your commands, plus your actions during CONNECT mode, and automatically generates a script program that mimics what it observed. You should think of this feature as a script-writing ASSISTANT since, as you will see later in this section, the result generally needs some editing to make it both secure and flexible. The script recorder is controlled by the new LEARN command:

    LEARN [ /ON /OFF /CLOSE ] [ filename ]
    If you give a filename, the file is opened for subsequent recording. The /ON switch enables recording to the current file (if any); /OFF disables recording. /CLOSE closes the current script recording file (if any). If you give a filename without any switches, /ON is assumed.

    The /OFF and /ON switches let you turn recording off and on during a session without closing the file.

    When recording:

    Thus the script recorder is inherently line-oriented. It can't be used to script character-oriented interactions like typing Space to a "More?" prompt or editing a text file with VI or EMACS.

    But it has advantages too; for example it takes control characters into account that might not be visible to you otherwise, and it automatically converts control characters in both the input and output streams to the appropriate notation. It can tell, for example that the "" prompt on the left margin in UNIX is really {\{13}\{10}$ }, whereas in VMS it might be {\{13}\{10}\{13}$ }. These sequences are detected and recorded automatically.

    A learned script should execute correctly when you give a TAKE command for it. However, it is usually appropriate to edit the script a bit. The most important change would be to remove any passwords from it. For example, if the script contains:

      INPUT 9 {\{13}\{10}Password: }
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT bigsecret\{13}
    

    you should replace this by something like:

      INPUT 9 {\{13}\{10}Password: }
      IF FAIL STOP 1 INPUT timeout
      ASKQ pswd Please type your password:
      PAUSE 1
      OUTPUT \m(pswd)\{13}
    

    The LEARN command can't do this for you since it knows nothing about "content"; it only knows about lines and can't be expected to parse or understand them -- after all, the Password prompt might be in some other language. So remember: if you use the LEARN command to record a login script, be sure edit the resulting file to remove any passwords. Also be sure to delete any backup copies your editor or OS might have made of the file.

    Other manual adjustments might also be appropriate:

    Here is a sample script generated by Kermit ("learn vms.ksc") in which a Telnet connection is made to a VMS computer, the user logs in, starts Kermit on VMS, sends it a file, and then logs out:

      ; Scriptfile: vms.ksc
      ; Directory:  /usr/olga
      ; Recorded:   20001124 15:21:23
    
      SET HOST /NETWORK:TCP vms.xyzcorp.com
      IF FAIL STOP 1 Connection failed
    
      INPUT 7 {\{13}\{10}\{13}Username: }
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT olga\{13}
      INPUT 3 {\{13}\{10}\{13}Password: }
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT secret\{13}
      INPUT 18 {\{13}\{10}\{13}$ }
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT set default [.incoming]\{13}
      INPUT 12 {\{13}\{10}\{13}$ }
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT kermit\{13}
      INPUT 15 {\{13}\{10}\{13}ALTO:[OLGA.INCOMING] C-Kermit>}
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT receive\{13}
      send myfile.txt
    
      INPUT 18 {\{13}\{10}\{13}ALTO:[OLGA.INCOMING] C-Kermit>}
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT exit\{13}
      INPUT 6 {\{13}\{10}\{13}$ }
      IF FAIL STOP 1 INPUT timeout
      PAUSE 1
      OUTPUT logout\{13}
      close
      exit
    

    The commands generated by Kermit during CONNECT (INPUT, IF FAIL, PAUSE, and OUTPUT) have uppercase keywords; the commands typed by the user are in whatever form the user typed them (in this case, lowercase).

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    8.12. Pattern Matching

    A pattern is a character string that is used to match other strings. Patterns can contain metacharacters that represent special actions like "match any single character", "match zero or more characters", "match any single character from a list", and so on. The best known application of patterns is in file specifications that contain wildcards, as in "send *.txt", meaning "send all files whose names end with .txt".

    Patterns are also used in increasingly many other ways, to the extent it is useful to point out certain important distinctions in the ways in which they are used:

    Anchored Patterns
    If an anchored pattern does not begin with "*", it must match the beginning of the string, and if it does not end with "*", it must match the end of the string. For example, the anchored pattern "abc" matches only the string "abc", not "abcde" or "xyzabc" or "abcabc". The anchored pattern "abc*" matches any string that starts with "abc"; the anchored pattern "*abc" matches any string that ends with "abc"; the anchored pattern "*abc*" matches any string that contains "abc" (including any that start and/or end with it).

    Floating Patterns
    A floating pattern matches any string that contains a substring that matches the pattern. In other words, a floating pattern has an implied "*" at the beginning and end. You can anchor a floating pattern to the beginning by starting it with "^", and you can anchor it to the end by ending it with "$" (see examples below).

    Wildcards
    A wildcard is an anchored pattern that has the additional property that "*" does not match directory separators.

    This terminology lets us describe Kermit's commands with a bit more precision. When a pattern is used for matching filenames, it is a wildcard, except in the TEXT-PATTERNS and BINARY-PATTERNS lists and /EXCEPT: clauses, in which case directory separators are not significant (for example, a BINARY-PATTERN of "*.exe" matches any file whose name ends in .exe, no matter how deeply it might be buried in subdirectories). When Kermit parses a file specification directly, however, it uses the strict wildcard definition. For example, "send a*b" sends all files whose names start with "a" and end with "b" in the current directory, and not any files whose names end with "b" that happen to be in subdirectories whose names start with "a". And as noted, wildcards are anchored, so "delete foo" deletes the file named "foo", and not all files whose names happen to contain "foo".

    Most other patterns are anchored. For example:

      if match abc bc ...
    

    does not succeed (and you would be surprised if it did!). In fact, the only floating patterns are the ones used by commands or functions that search for patterns in files, arrays, or strings. These include:

    Thus these are the only contexts in which explicit anchors ("^" and "$") may be used:

    grep abc *.txt
    Prints all lines containing "abc" in all files whose names end with ".txt".

    grep ^abc *.txt
    Prints all lines that start with "abc" in all ".txt" files.

    grep abc$ *.txt
    Prints all lines that end with "abc" in all ".txt" files.

    grep ^a*z$ *.txt
    Prints all lines that start with "a" and end with "z" in all ".txt" files.

    Similarly for TYPE /PAGE, /fsearch(), /frsearch(), and \farraylook().

    Here is a brief summary of anchored and floating pattern equivalences:

      Anchored   Floating
        abc       ^abc$
        *abc      abc$
        abc*      ^abc
        *abc*     abc
    

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    8.13. Dates and Times

    C-Kermit's comprehension of date-time formats is considerably expanded in version 8.0. Any command that reads dates, including the DATE command itself, or any switch, such as the /BEFORE: and /AFTER: switches, or any function such as \fcvtdate(), now can understand dates and times expressed in any ISO 8601 format, in Unix "asctime" format, in FTP MDTM format, and in practically any format used in RFC 822 or RFC 2822 electronic mail, with or without timezones, and in a great many other formats as well. HELP DATE briefly summarizes the acceptable date-time formats.

    Furthermore, C-Kermit 8.0 includes a new and easy-to-use form of date-time arithmetic, in which any date or time can be combined with a "delta time", to add or subtract the desired time interval (years, months, weeks, days, hours, minutes, seconds) to/from the given date. And new functions are available to compare dates and to compute their differences.

    As you can imagine, all this requires quite a bit of "syntax". The basic format is:

      [ date ] [ time ] [ delta ]
    

    Each field is optional, but in most cases (depending on the context) there must be at least one field. If a date is given, it must come first. If no date is given, the current date is assumed. If no time is given, an appropriate time is supplied depending on whether a date was supplied. If no delta is given, no arithmetic is done. If a delta is given without a date or time, the current date and time are used as the base.

    Date-time-delta fields are likely to contain spaces (although they need not; space-free forms are always available). Therefore, in most contexts -- and notably as switch arguments -- date-time information must be enclosed in braces or doublequotes, for example:

      send /after:"8-Aug-2001 12:00 UTC" *.txt
    

    Kermit's standard internal format for dates and times is:

      yyyymmdd hh:mm:ss
    

    for example:

      20010208 10:28:01
    

    Date-times can always be given in this format. yyyy is the 4-digit year, mm is the two-digit month (1-12; supply leading zero for Jan-Sep), dd is the 2-digit day (leading zero for 1-9), hh is the hour (0-23), mm the minute (0-59), ss the second (0-59), each with leading zero if less than the field width. The date and time can be separated by a space, an underscore, a colon, or the letter T. The time is in 24-hour format. Thus the various quantities are at the following fixed positions:

    Position  Contents                    
       1-4    Year   (4 digits, 0000-9999)
       5-6 	  Month  (2 digits, 1-12)
       7-8 	  Day    (2 digits, 1-31) 
       9   	  Date-Time Separator (space, :, _, or the letter T) 
      10-11	  Hour   (2 digits, 0-23)
      12   	  Hour-Minute Separator (colon) 
      13-14	  Minute (2 digits, 0-59)
      15   	  Minute-Second Separator (colon)
      16-17	  Second (2 digits, 0-59)
    

    Example:

      19800526 13:07:12  26 May 1980, 13:07:12 (1:07:12PM)
    

    This is the format produced by the DATE command and by any function that returns a date-time. It is suitable for lexical comparison and sorting, and for use as a date-time in any Kermit command. When this format is given as input to a command or function, various date-time separators (as noted) are accepted:

      19800526 13:07:12  26 May 1980, 13:07:12 (1:07:12PM)
      20010208_10:28:35  2 February 2001, 10:28:35 AM
      18580101:12:00:00  1 January 1858, noon
      20110208T00:00:00  2 February 2011, midnight
    

    Certain other special date-time formats that are encountered on computer networks are recognized:

    Asctime Format
    This is a fixed format used by Unix, named after Unix's asctime() ("ASCII time") function. It is always exactly 24 characters long. Example: Fri Aug 10 16:38:01 2001

    Asctime with Timezone
    This is like Asctime format, but includes a 3-character timezone between the time and year. It is exactly 28 characters long. Example: Fri Aug 10 16:38:01 GMT 2001

    E-Mail Format
    E-mail date-time formats are defined in RFC 2822 with a fair amount of flexibility and options. The following examples are typical of e-mails and HTTP (web-page) headers:
      Sat, 14 Jul 2001 11:49:29                (No timezone)
      Fri, 24 Mar 2000 14:19:59 EST            (Symbolic timezone)
      Tue, 26 Jun 2001 10:19:45 -0400 (EDT)    (GMT Offset + comment)
    

    FTP MDTM Format
    This is the date-time format supplied by FTP servers that support the (not yet standard but widely used nevertheless) MDTM command, by which the FTP client asks for a file's modification time:

      yyyymmddhhmmss[.ffff]
    

    where yyyy is the 4-digit year, mm is the 2-digit month, and so on, exactly 14 digits long. An optional fractional part (fraction of second) may also be included, separated by a decimal point (period). Kermit rounds to the nearest second. Example:

      20020208102835.515                       (8 February 2002 10:28:36 AM)
    

    8.13.1. The Date

    The date, if given, must precede the time and/or delta, and can be in many, many formats. For starters, you can use several symbolic date names in place of actual dates:

    NOW
    This is replaced by the current date and time. The time can not be overriden (if you want to supply a specific time, use TODAY rather than NOW).

    TODAY
    This is replaced by the current date and a default time of 00:00:00 is supplied, but can be overridden by a specific time; for example, if today is 8 February 2002, then "TODAY" is "20020802 00:00:00" but "TODAY 10:28" is "20020802 10:28:00".

    TOMORROW
    Like TODAY, but one day later (if today is 8 February 2002, then "TOMORROW" is "20020803 00:00:00" but "TOMORROW 16:30" is "20020803 16:30:00").

    YESTERDAY
    Like TODAY, but one day earlier.

    MONDAY, TUESDAY, WEDNESDAY, ..., SUNDAY
    The date on the given day of the week, today or later. A default time of 00:00:00 is supplied but can be overridden. Example: "SATURDAY 12:00" means next Saturday (or today, if today is Saturday) at noon.

    You can give an explicit date in almost any conceivable format, but there are some rules:

    Various date-field separators are accepted: hyphen, slash, space, underscore, period. The same field separator (if any) must be used in both places; for example 18-Sep-2001 but not 18-Sep/2001. Months can be numeric (1-12) or English names or abbreviations. Month name abbreviations are normally three letters, e.g. Apr, May, Jun, Jul. Capitalization doesn't matter.

    Here are a few examples:

      18 Sep 2001                              (English month, abbreviated)
      18 September 2001                        (English month, spelled out)
      2001 Sept 18                             (Year, month, day)
      18-Sep-2001                              (With hyphens)
      18/09/2001                               (All numeric with slashes)
      18.09.2001                               (Ditto, with periods)
      18_09_2001                               (Ditto, with underscores)
      09/18/2001                               (See below)
      2001/09/18                               (See below)
      September 18, 2001                       (Correspondence style)
      Sep-18-2001                              (Month-day-year)
      20010918                                 (Numeric, no separators)
    

    You can also include the day of the week with a specific date, in which case it is accepted (if it is a valid day name), but not verified to agree with the given date:

      Tue, 18 Sep 2001                         (Abbreviated, with comma)
      Tue,18 Sep 2001                          (Comma but no space)
      Tue 18 Sep 2001                          (Abbreviated, no comma)
      Tuesday 18 Sep 2001                      (Spelled out)
      Tuesday, 18 Sep 2001                     (etc)
      Friday, 18 Sep 2001                      (Accepted even if not Friday)
    

    In all-numeric dates with the year last, such as 18/09/2001, Kermit identifies the year because it's 4 digits, then decides which of the other two numbers is the month or day based on its value. If both are 12 or less and are unequal, the date is ambiguous and is rejected. In all-numeric dates with the year first, the second field is always the month and the third is the day. The month never comes last. A date with no separators is accepted only if it is all numeric and has exactly eight digits, and is assumed to be in yyyymmdd format.

      20010918                                 (18-Sep-2001 00:00:00)
    
    or 14 digits (as in FTP MDTM format):

      20010918123456                           (18-Sep-2001 12:34:56)
    

    You can always avoid ambiguity by putting the year first, or by using an English, rather than numeric, month. A date such as 09/08/2001 would be ambiguous but 2001/09/08 is not, nor is 09-Aug-2001.

    Until the late 1990s, it was common to encounter 2-digit years, and these are found to this day in old e-mails and other documents. Kermit accepts these dates if they have English months, and interprets them according to the windowing rules of RFC 2822: "If a two digit year is encountered whose value is between 00 and 49, the year is interpreted by adding 2000, ending up with a value between 2000 and 2049. If a two digit year is encountered with a value between 50 and 99, or any three digit year is encountered, the year is interpreted by adding 1900."

    If you need to specify a year prior to 1000, use leading zeros to ensure it is not misinterpreted as a "non-Y2K-compliant" modern year:

      7-Oct-77                                 (19771007 00:00:00)
      7-Oct-0077                               (00771007 00:00:00)
    

    8.13.2. The Time

    The basic time format is hh:mm:dd; that is hours, minutes, seconds, separated by colons, perhaps with an optional fractional second separated by a decimal point (period). The hours are in 24-hour format; 12 is noon, 13 is 1pm, and so on. Fields omitted from the right default to zero. Fields can be omitted from the left or middle by including the field's terminating colon. Examples:

      11:59:59                                 (11:59:59 AM)
      11:59                                    (11:59:00 AM)
      11                                       (11:00:00 AM)
      11:59:59.33                              (11:59:59 AM)
      11:59:59.66                              (Noon)
      03:21:00                                 (3:21:00 AM)
      3:21:00                                  (3:21:00 AM)  
      15:21:00                                 (3:21:00 PM)
      :21:00                                   (00:21:00 AM)
      ::01                                     (00:00:01 AM)
      11::59                                   (11:00:59 AM)
    

    Leading zeros can be omitted, but it is customary and more readable to keep them in the minute and second fields:

      03:02:01                                 (03:02:01 AM)
      3:02:01                                  (03:02:01 AM)
      3:2:1                                    (03:02:01 AM)
    

    AM/PM notation is accepted if you wish to use it:

      11:59:59                                 (11:59:59 AM)
      11:59:59AM                               (11:59:59 AM)
      11:59:59A.M.                             (11:59:59 AM)
      11:59:59am                               (11:59:59 AM)
      11:59:59a.m.                             (11:59:59 AM)
      11:59:59PM                               (11:59:59 PM = 23:59:59)
      11:59:59P.M.                             (11:59:59 PM = 23:59:59)
      11:59:59pm                               (11:59:59 PM = 23:59:59)
      11:59:59p.m.                             (11:59:59 PM = 23:59:59)
    

    You can omit the colons if you wish, in which case Kermit uses the following rules to interpret the time:

    1. 6 digits is hh:mm:ss, e.g. 123456 is 12:34:56.
    2. 5 digits is h:mm:ss, e.g. 12345 is 1:23:45.
    3. 4 digits is hh:mm, e.g. 1234 is 12:34.
    4. 3 digits is h:mm, e.g. 123 is 1:23.
    5. 2 digits is hh, e.g. 12 is 12:00.
    6. 1 digit is h (the hour), e.g. 1 is 1:00.

    Examples:

      1                                        (01:00:00 AM)
      10                                       (10:00:00 AM)
      230                                      (02:30:00 AM)
      230pm                                    (02:30:00 PM = 14:30:00)
      1115                                     (11:15:00 AM)
      2315                                     (11:15:00 PM = 23:15:00 PM)
      23150                                    (02:31:50 AM)
      231500                                   (23:15:00 PM)
    

    8.13.3. Time Zones

    If a time is given, it can (but need not) be followed by a time zone designator. If no time zone is included, the time is treated as local time and no timezone conversions are performed.

    The preferred time zone designator is the UTC Offset, as specified in RFC 2822: a plus sign or minus sign immediately followed by exactly four decimal digits, signifying the difference in hh (hours) and mm (minutes) from Universal Coordinated Time (UTC, also known as Greenwich Mean Time, or GMT), with negative numbers to the West and positive numbers to the East. For example:

      Fri, 13 Jul 2001 12:54:29 -0700
    

    indicates a local time of 12:54:29 that is 07 hours and 00 minutes behind (less than, East of) Universal Time. The space is optional, so the example could also be written as:

      Fri, 13 Jul 2001 12:54:29-0700
    

    The following symbolic time zones are also accepted, as specified by RFC 2822 and/or in ISO 8601:

      GMT  =  +0000       Greenwich Mean Time
      Z    =  +0000       Zulu (Zero Meridian) Time
      UTC  =  +0000       Universal Coordinated Time
      UT   =  +0000       Universal Time
      EDT  =  -0400       Eastern (USA) Daylight Time
      EST  =  -0500       Eastern (USA) Standard Time
      CDT  =  -0500       Central (USA) Daylight Time
      CST  =  -0600       Central (USA) Standard Time
      MDT  =  -0600       Mountain (USA) Daylight Time
      MST  =  -0700       Mountain (USA) Standard Time
      PDT  =  -0700       Pacific (USA) Daylight Time
      PST  =  -0800       Pacific (USA) Standard Time
    

    Note that GMT, Z, UTC, and UT all express the same concept: standard (not daylight) time at the Zero Meridian. UTC, by the way, is an international standard symbol and does not correspond to the order of the English words, Universal Coordinated Time, but it happens to have the same initial letters as these words. Of course hundreds of other symbolic timezones and variations exist, but they are not standardized, and are therefore not supported by Kermit.

    When a time zone is included with a time, the time is converted to local time. In case the conversion crosses a midnight boundary, the date is adjusted accordingly. Examples converting to EST (Eastern USA Standard Time = -0500):

     11:30:00      =  11:30:00
     11:30:00 EST  =  11:30:00
     11:30:00 GMT  =  06:30:00
     11:30:00 PST  =  14:30:00
     11:30:00Z     =  06:30:00
     11:30PM GMT   =  18:30:00
     11:30 -0500   =  11:30:00
     11:30 -0800   =  08:30:00
     11:30 +0200   =  04:30:00
    

    Unlike most of Kermit's other date-time conversions, timezone knowledge (specifically, the offset of local time from UTC) is embodied in the underlying operating system, not in Kermit itself, and any conversion errors in this department are the fault of the OS. For example, most UNIX platforms do not perform conversions for years prior to 1970.

    8.13.4. Delta Time

    Date/time expressions can be composed of a date and/or time and a delta time, or a delta time by itself. When a delta time is given by itself, it is relative to the current local date and time. Delta times have the following general format:

      {+,-}[number units][hh[:mm[:ss]]]
    

    In other words, a delta time always starts with a plus or minus sign, which is followed by a "part1", a "part2", or both. The "part1", if given, specifies a number of days, weeks, months, or years; "part2" specifies a time in hh:mm:ss notation. In arithmetic terms, these represents some number of days or other big time units, and then a fraction of a day expressed as hours, minutes, and seconds; these are to be added to or subtracted from the given (or implied) date and time. The syntax is somewhat flexible, as shown by the following examples:

      +1 day                (Plus one day)
      +1day                 (Ditto)
      +1d                   (Ditto)
      + 1 day               (Ditto)
      + 1 day 3:00          (Plus one day and 3 hours)
      +1d3:00               (Ditto)
      +1d3                  (Ditto)
      +3:00:00              (Plus 3 hours)
      +3:00                 (Ditto)
      +3                    (Ditto)
      +2 days               (Plus 2 days)
      -12 days 7:14:22      (Minus 12 days, 7 hours, 14 minutes, and 22 seconds)
    

    The words "week", "month", and "year" can be used like "day" in the examples above. A week is exactly equivalent to 7 days. When months are specified, the numeric month number of the date is incremented or decremented by the given number, and the year and day adjusted accordingly if necessary (for example, 31-Jan-2001 +1month = 03-Mar-2001 because February does not have 31 days). When years are specified, they are added or subtracted to the base year. Examples (assuming the current date is 10-Aug-2001 and the current time is 19:21:11):

      18-Sep-2001 +1day              (20010918 00:00:00)
      today +1day                    (20010811 00:00:00)
      now+1d                         (20010811 19:21:11)
      + 1 day                        (20010811 19:21:11)
      + 1 day 3:14:42                (20010811 22:35:54)
      + 7 weeks                      (20010928 19:21:11)
      +1d3:14:42                     (20010811 22:35:54)
      +1w3:14:42                     (20010817 22:35:54)
      +1m3:14:42                     (20010910 22:35:54)
      +1y3:14:42                     (20020810 22:35:54)
      2 feb 2001 + 10 years          (20110208 00:00:00)
      2001-02-08 +10y12              (20110208 12:00:00)
      31-dec-1999 23:59:59+00:00:01  (20000101 00:00:00)
      28-feb-1996 +1day              (19960229 00:00:00) (leap year)
      28-feb-1997 +1day              (19970301 00:00:00) (nonleap year)
      28-feb-1997 +1month            (19970328 00:00:00)
      28-feb-1997 +1month 11:59:59   (19970328 11:59:59)
      28-feb-1997 +20years           (20170228 00:00:00)
      28-feb-1997 +8000years         (99970228 00:00:00)
    

    For compatibility with VMS, the following special delta-time format is also accepted:

      +number-hh:mm:ss
      -number-hh:mm:ss
    

    (no spaces). The hyphen after the number indicates days. It corresponds exactly to the Kermit notation:

      +numberdhh:mm:ss
      -numberdhh:mm:ss
    

    The following forms all indicate exactly the same date and time:

      18-Sep-2001 12:34:56 +1-3:23:01
      18-Sep-2001 12:34:56 +1d3:23:01
      18-Sep-2001 12:34:56 +1 day 3:23:01
    

    and mean "add a day plus 3 hours, 23 minutes, and 1 second" to the given date.

    Note that delta times are not at all the same as UTC offsets; the former specifies an adjustment to the given date/time and the latter specifies that the local time is a particular distance from Universal Time, for example:

      11-Aug-2001 12:34:56 -0800          (20010811 16:34:56 -- UTC Offset)
      11-Aug-2001 12:34:56 -08:00         (20010811 04:34:56 -- Delta time)
    

    If you give a time followed by a modifier that starts with a + or - sign, how does Kermit know whether it's a UTC offset or a delta time? It is treated as a UTC offset if the sign is followed by exactly four decimal digits; otherwise it is a delta time. Examples (for USA Eastern Daylight Time):

      11-Aug-2001 12:34:56 -0800          (20010811 16:34:56 -- UTC Offset)
      11-Aug-2001 12:34:56 -08:00         (20010811 04:34:56 -- Delta time)
      11-Aug-2001 12:34:56 -800           (20010811 04:34:56 -- Delta time)
      11-Aug-2001 12:34:56 -8             (20010811 04:34:56 -- Delta time)
    

    The first example says that at some unknown place which is 8 hours ahead of Universal Time, the time is 12:34:56, and this corresponds to 16:34:56 in Eastern Daylight time. The second example says to subtract 8 hours from the local time. The third and fourth are delta times because, even though a colon is not included, the time does not consist of exactly 4 digits.

    When a delta time is written after a timezone, however, there is no ambiguity and no syntax distinction is required:

      11-Aug-2001 12:34:56 -0800 -0800    (20010811 08:34:56)
      11-Aug-2001 12:34:56 -0800 -08:00   (Ditto)
      11-Aug-2001 12:34:56 -08:00 -08:00  (Illegal)
    

    8.13.5. The DATE Command

    Obviously a great many combinations of date, time, time zone, and delta time are possible, as well as many formatting options. The purpose of all this flexibility is to comply with as many standards as possible -- Internet RFCs, ISO standards, and proven corporate standards -- as well as with notations commonly used by real people, in order that dates and times from the widest variety of sources can be assigned to a variable and used in any date-time field in any Kermit command.

    You can test any date-and/or-time format with the DATE command, which converts it to standard yyyymmdd hh:mm:ss format if it is understood, or else gives an explicit error message (rather than just "BAD DATE" as in previous C-Kermit releases) to indicate what is wrong with it. Examples (on Tuesday, 31 July 2001 in New York City, Eastern Daylight Time, UTC -0400):

      DATE command argument                   Result           
      12:30                                   20010731 12:30:00
      12:30:01                                20010731 12:30:01
      12:30:01.5                              20010731 12:30:02
      1230                                    20010731 12:30:00
      230                                     20010731 02:30:00
      230+1d                                  20010801 02:30:00
      230+1d3:00                              20010801 05:30:00
      20010718 19:21:15                       20010718 19:21:15
      20010718_192115                         20010718 19:21:15
      20010718T192115                         20010718 19:21:15
      18 Jul 2001 +0400                       20010717 23:59:59
      18 Jul 2001 192115                      20010718 19:21:15
      18 Jul 2001 192115.8                    20010718 19:21:16
      18-Jul-2001T1921                        20010718 19:21:00
      18-Jul-2001 1921Z                       20010718 15:21:00
      18-Jul-2001 1921 GMT                    20010718 15:21:00
      18-Jul-2001 1921 UTC                    20010718 15:21:00
      18-Jul-2001 1921 Z                      20010718 15:21:00
      18-Jul-2001 1921Z                       20010718 15:21:00
      18-Jul-2001 1921 -04:00:00              20010718 19:21:00
      21-Jul-2001_08:20:00am                  20010721 08:20:00
      21-Jul-2001_8:20:00P.M.                 20010721 20:20:00
      Fri Jul 20 11:26:25 2001                20010720 11:26:25
      Fri Jul 20 11:26:25 GMT 2001            20010720 07:26:25
      Sun, 9 Apr 2000 06:46:46 +0100          20000409 01:46:46
      Sunday, 9 Apr 2000 06:46:46 +0100       20000409 01:46:46
      now                                     20010731 19:41:12
      today                                   20010731 00:00:00
      today 09:00                             20010731 09:00:00
      tomorrow                                20010801 00:00:00
      tomorrow 09:00                          20010801 09:00:00
      tomorrow 09:00 GMT                      20010801 05:00:00
      yesterday                               20010730 00:00:00
      yesterday 09:00                         20010730 09:00:00
      + 3 days                                20010803 00:00:00
      +3 days                                 20010803 00:00:00
      +3days                                  20010803 00:00:00
      + 3days                                 20010803 00:00:00
      + 3 days 09:00                          20010803 09:00:00
      + 2 weeks                               20010814 00:00:00
      + 1 month                               20010831 00:00:00
      - 7 months                              20001231 00:00:00
      + 10 years                              20110731 00:00:00
      friday                                  20010803 00:00:00
      saturday                                20010804 00:00:00
      sunday                                  20010805 00:00:00
      monday                                  20010806 00:00:00
      tuesday                                 20010731 00:00:00
      wednesday                               20010801 00:00:00
      thursday                                20010802 00:00:00
      friday 07:00                            20010803 07:00:00
      thursday 1:00pm                         20010802 13:00:00
      thursday 1:00pm GMT                     20010802 09:00:00
      Thu, 10 Nov 94 10:50:47 EST             19941110 10:50:47
      Fri, 20 Oct 1995 18:35:15 -0400 (EDT)   19951020 18:35:15
      31/12/2001                              20011231 00:00:00
      12/31/2001                              20011231 00:00:00
      2001-July-20                            20010720 00:00:00
      2001-September-30                       20010930 00:00:00
      30-September-2001                       20010930 00:00:00
      Sep 30, 2001 12:34:56                   20010930 12:34:56
      September 30, 2001                      20010930 00:00:00
      September 30, 2001 630                  20010930 06:30:00
      September 30 2001 630                   20010930 06:30:00
      Sep-30-2001 12:34:59                    20010930 12:34:59
      20010807113542.014                      20010807 11:35.42
      20010807113542.014Z                     20010807 07:35:42
    

    8.13.6. New Date-Time Functions

    In the following descriptions, date-time function arguments are the same free-format date-time strings discussed above, with the same defaults for missing fields. They are automatically converted to standard format internally prior to processing.

    \fcvtdate(d1)
    Converts the date-time d1 to standard format and local time. This function is not new, but now it accepts a wider range of argument formats that can include timezones and/or delta times. If the first argument is omitted, the current date and time are assumed. The optional second argument is a format code for the result:

    n1 = 1: yyyy-mmm-dd hh:mm:ss (mmm = English 3-letter month abbreviation)
    n1 = 2: dd-mmm-yyyy hh:mm:ss (ditto)
    n1 = 3: yyyymmddhhmmss (all numeric)

    \futcdate(d1)
    Converts the date-time d1 to Universal Coordinated Time (UTC), also known as GMT or Zulu or Zero-Meridian time. The default d1 is NOW. If d1 is a valid date-time, the UTC result is returned in standard format, yyyymmdd hh:ss:mm.

    \fcmpdates(d1,d2)
    Compares two free-format date-times, d1 and d2, and, if both arguments are valid, returns a number: -1 if d1 is earlier than (before) d2; 0 if d1 is the same as d2; 1 if d1 is later than (after) d2.

    \fdiffdates(d1,d2)
    Computes the difference between two free-format date-times, d1 and d2. If both arguments are valid, returns a delta time which is negative if d1 is earlier than (before) d2 and positive otherwise. If d1 and d2 are equal, the result is "+0:00". Otherwise, the result consists of the number of days, hours, minutes, and seconds that separate the two date-times. If the number of days is zero, it is omitted. If the number of days is nonzero but the hours, minutes, and seconds are all zero, the time is omitted. if the seconds are zero, they are omitted.

    \fdelta2secs(dt)
    Converts a delta time to seconds. For example, "+1d00:00:01" to 86401. Valid delta times must start with a + or - sign. Days are accepted as time units, but not years, months, or weeks. If the result would overflow a computer long word (as would happen with 32-bit long words when the number of days is greater than 24854), the function fails.

    HINT: Although Kermit has a number of built-in date and time variables, it doesn't have a single one suitable for writing a timestamp. For this you would normally use something like "\v(ndate) \v(time)". But \fcvtdate() (with no arguments) is equivalent: it returns the current date and time in yyyymmdd hh:mm:ss format, suitable for time stamping.

    8.13.7. Date-Time Programming Examples

    Here's a macro that converts any date-time to UTC, which you might use if C-Kermit didn't already have a \futcdate() function:

      define utcdate {
          .local := \fcvtdate(\%*)                 ; 1.
          .tmp := \fcvtdate(\m(local)UTC)          ; 2.
          .offset := \fdiffdate(\m(local),\m(tmp)) ; 3.
          .utc := \fcvtdate(\m(local)\m(offset))   ; 4.
          sho mac utc                              ; 5.
      }
    

    Brief explanation: Line 1 converts the macro argument, a free-format date-time, to standard-format local time. Line 2 appends the "UTC" timezone to the local time and converts the result to local time. In other words, we take the same time as the local time, but pretend it's UTC time, and convert it to local time. For example, if New York time is 4 hours ahead of UTC, then 6:00pm New York time is 2:00pm UTC. Line 3 gets the difference of the two results (e.g. "+04:00"). Line 4 appends the difference (delta time) to the local time, and converts it again, which adds (or subtracts) the UTC offset to the given time. Line 5 displays the result.

    Here's a script that opens a web page, gets its headers into an array, scans the array for the "Last-Modified:" header, and interprets it:

      http open www.columbia.edu
      if fail stop 1 HTTP OPEN failed
      http /array:a head index.html /dev/null
      if fail stop 1 HTTP GET failed
      show array a
      for \%i 1 \fdim(&a) 1 {
          .\%x := \findex(:,\&a[\%i])
          if not \%x continue
          .tag := \fleft(\&a[\%i],\%x-1)
          .val := \fltrim(\fsubstr(\&a[\%i],\%x+1))
          if ( eq "\m(tag)" "Last-Modified" ) {
              echo HTTP Date: \m(val)
              .rdate := \fcvtdate(\m(val))
              echo {Standard Date (local): \m(rdate)}
              echo {Standard Date (UTC):   \futcdate(\m(rdate))}
              break
          }
      }
      http close
    

    The result:

      HTTP Date: Mon, 13 Aug 2001 20:05:42 GMT
      Standard Date (local): 20010813 16:05:42
      Standard Date (UTC):   20010813 20:05:42
    

    As you can see, Kermit had no trouble decoding the date-time-string from the website, converting to local time, and converting back to UTC with no conflicts or loss of information. If it had been in any other known format, the result would have been the same.

    Now suppose we want to download the web page only if it is newer than our local copy. The \fdate(filename) function (which returns the modification date-time of the given file) and the new \fcmpdates() function make it easy. Insert the following just before the BREAK statement:

      if ( < 0 \fcmpdates(\m(rdate),\fdate(index.html)) ) {
         echo GETTING index.html...
         http get index.html index.html
         if success echo HTTP GET OK
      } else {
         echo index.html: no update needed
      }
      http close
      exit
    

    This says, "if 0 is less than the comparison of the remote file date and the local file date, get the remote file, otherwise skip it." And it automatically reconciles the time-zone difference (if any).

    It would be nice to be able to extend this script into a general-purpose website updater, but unfortunately HTTP protocol doesn't provide any mechanism for the client to ask the server for a list of files, recursive or otherwise.

    [ Top ] [ Contents ] [ C-Kermit Home ] [ Kermit Home ]

    8.14. Trapping Keyboard Interruption

    Normally when you type Ctrl-C and Kermit is in command mode (as opposed to CONNECT mode) with COMMAND INTERRUPTION ON (as it is unless you have set it OFF), Kermit interrupts any command that is currently in progress, and if a command file or macro is executing, rolls the command stack back to top level, closing all open command files, deactivating all macros, deallocating all local variables and arrays, and leaving you at the command prompt.

    Suppose, however, you want certain actions to occur when a script is interrupted; for example, closing open files, writing log entries, or displaying summary results. You can do this by defining a macro named ON_CTRLC. When Ctrl-C is detected, and a macro with this name is defined, Kermit executes it from the current command level, thus giving it full access to the environment in which the interruption occurred, including local variables and open files. Only when the ON_CTRLC macro completes execution is the command stack rolled back to top level.

    Once the ON_CTRLC macro is defined, it can be executed only once. This is to prevent recursion if the user types Ctrl-C while the ON_CTRLC macro is executing. If you type Ctrl-C while the Ctrl-C macro is active, this does not start a new copy of ON_CTRLC; rather, it returns to the top-level command prompt. After the ON_CTRLC macro returns, it has been removed from the macro table so if you want to use it again or install a different Ctrl-C trap, you must execute a new DEFINE ON_CTRLC command. In any case, as always when you interrupt a script with Ctrl-C, its completion status is FAILURE.

    Normally the ON_CTRLC macro would be defined in the command file or macro to which it applies, and should be declared LOCAL. This way, if the command file or macro completes successfully without being interrupted, the ON_CTRLC definition disappears automatically. Otherwise the definition would still be valid and the macro would be executed, probably out of context, the next time you typed Ctrl-C.

    Here's a simple example of a command file that sets a Ctrl-C trap for itself:

      local on_ctrlc              ; Make Ctrl-C trap local to this command file.
      define on_ctrlc {           ; Define the ON_CTRLC macro.
          echo Interrupted at \v(time).
          echo Iterations: \%n
      }
      xecho Type Ctrl-C to quit
      for \%n 1 999 1 {           ; Prints a dot every second until interrupted.
          sleep 1
          xecho .
      }
      echo Finished normally at \v(time) ; Get here only if not interrupted.
      decrement \%n
      echo Iterations: \%n
    

    This prints a summary no matter whether it completes normally or is interrupted from the keyboard. In both cases the trap is automatically removed afterwards.

    For an example of how to use ON_CTRLC to debug scripts, see Section 8.1.

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    9. S-EXPRESSIONS

    This section is primarily for those who want to write calculation-intensive scripts, especially if they require floating-point arithmetic, and/or for those who are familiar with the LISP programming language.

    Ever since C-Kermit version 5 was released in 1988, scripting has been one of its major attractions, and arithmetic is a key part of it. Versions 5 and 6 included integer arithmetic only, using traditional algebraic notation, e.g.:

      echo \fevaluate(3*(2+7)/2)
      13
    

    C-Kermit 7.0 added support for floating-point arithmetic, but only through function calls:

      echo \ffpdivide(\ffpmultiply(3.0,\ffpadd(2.0,7.0)),2.0)
      13.5
    

    C-Kermit 8.0 introduces a third form of arithmetic that treats integers and floating-point numbers uniformly, is easier to read and write, and executes very quickly:

      (/ (* 3 (+ 2 7)) 2)
      13.5
    

    But first some background.

    The Kermit command and scripting language differs from true programming languages (such as C or Fortran) in many ways; one of the most prominent differences is the way in which variables are distinguished from constants. In a command language, words are taken literally; for example, the Unix shell:

      cat foo.bar
    

    displays the file named foo.bar. Whereas in a programming language like C, words are assumed to be variables:

      s = foo.bar;    /* Assigns the value of foo.bar to the variable s */
    

    To make a programming language take words literally, you have to quote or "escape" them:

      s = "foo.bar";  /* Assigns a pointer to the string "foo.bar" to the variable s */
    

    The opposite holds for command languages: to get them to treat a word as a variable rather than a constant, you have to escape them. For example, in the Unix shell:

      foo=123         ; Assign value 123 to variable foo.
      echo foo        ; Prints "foo"
      echo $foo       ; Prints "123"
    

    And in Kermit:

      define foo 123  ; Assign value 123 to variable foo.
      echo 123        ; This prints "123".
      echo foo        ; This prints "foo".
      echo \m(foo)    ; This prints "123".
    

    In other words, character strings (such as "foo" above) are interpreted as literal strings, rather than variable names, except in special commands like DEFINE that deal specifically with variable names (or in numeric contexts as explained in Section 8.2). The special "escape" character (dollar sign ($) for the shell, backslash (\) for Kermit) indicates that a variable is to be replaced by its value.

    The requirement to escape variable names in command languages normally does not impose any special hardship, but can add a considerable notational burden to arithmetic expressions, which are typically full of variables. Especially in Kermit when floating point numbers are involved, where you must use special \ffpxxx() functions, e.g. "\ffpadd(\m(a),\m(b))" rather than the simple "+" operator to add two floating-point numbers together, because the original arithmetic handler doesn't support floating point (this might change in the future). To illustrate, the general formula for the area of a triangle is:

      sqrt(s * (s - a) * (s - b) * (s - c))
    

    where a, b, and c are the lengths of the triangle's three sides and:

      s = (a + b + c) / 2
    

    Except in special cases (e.g. a = 3, b = 4, c = 5), the result has a fractional part so the computation must be done using floating-point arithmetic. We can create a Kermit 7.0 function for this as follows:

      def area {
          local s t1 t2 t3
          assign s \ffpdiv(\ffpadd(\ffpadd(\%1,\%2),\%3),2.0)
          assign t1 \ffpsub(\m(s),\%1)
          assign t2 \ffpsub(\m(s),\%2)
          assign t3 \ffpsub(\m(s),\%3)
          return \ffpsqrt(\ffpmul(\m(s),\ffpmul(\m(t1),\ffpmul(\m(t2),\m(t3)))))
      }
    

    But as you can see, this is rather cumbersome. Note, in particular, that arithmetic functions like \ffpadd(), \ffpmul(), etc, take exactly two operands (like their symbolic counterparts + and *), so obtaining the product of three or more numbers (as we do in this case) is awkward.

    Using the alternative S-Expression notation, we can reduce this to a form that is both easier to read and executes faster (the details are explained later):

      def newarea {
          (let s (/ (+ \%1 \%2 \%3) 2.0))
          (sqrt (* s (- s \%1) (- s \%2) (- s \%3)))
      }
    

    In both examples, the \%1..3 variables are the normal Kermit macro arguments, referenced by the normal escaping mechanism. For increased readability, we can also assign the macro arguments \%1, \%2, and \%3 to the letters a, b, and c corresponding to our formula:

    def newarea {
        (let a \%1 b \%2 c \%3)
        (let s (/ (+ a b c) 2.0))
        (sqrt (* s (- s a) (- s b) (- s c)))
    }
    

    And now the Kermit function reads almost like the original formula. Here Kermit behaves more like a regular programming language. In an S-Expression, macro names need not be escaped when they are used as the names of numeric variables.

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    9.1. What is an S-Expression?

    The S-Expression concept is borrowed from the Lisp programming language. "S-Expression" is short for Symbolic Expression (itself sometimes shortened to SEXP). S-Expressions provide a kind of Alternative Mini-Universe within the Kermit command language when the regular rules don't apply, a universe enclosed in parentheses.

    C-Kermit does not pretend to be a full Lisp interpreter; only the arithmetic parts of Lisp have been incorporated: S-Expressions that operate on numbers and return numeric values (plus extensibility features described in Section 9.8, which allow some degree of string processing).

    An S-Expression is a list of zero or more items, separated by spaces, within parentheses. Examples:

      ()
      (1)
      (a)
      (+ a 1)
      (* 2 a b)
    

    If the S-Expression is empty, it has the NIL (empty) value. If it is not empty and the first item is an operator (such as + or *), there can be zero or more subsequent items, called the operands:

      (+ 1 2)
    

    Here the operator is "+" and the operands are "1" and "2", and the value of the S-Expression is the value of the operation (in this case 3). The operator always comes first, which is different from the familiar algebraic notation; this because S-Expression operators can have different numbers of operands:

      (+ 1)
      (+ 1 2)
      (+ 1 2 3 4 5 6 7 8 9)
    

    If the first item in the S-Expression is not an operator, then it must be a variable or a number (or a macro; see Section 9.8), and the S-Expression can only contain one item; in this case, the S-Expression's value is the value of the variable or number:

      (a)
      (3)
    

    Operands can be numbers, variables that have numeric values, functions that return numbers, or other S-Expressions. To illustrate an S-Expression within an S-Expression, observe that:

      (+ 1 2)
    

    is equivalent to any of the following (plus an infinite number of others):

      (+ 1 (+ 1 1))
      (+ (- 3 2) (/ 14 (+ 3 4)))
    

    S-Expressions can be nested to any reasonable level; for example, the value of the following S-Expression is 64:

      (- (* (+ 2 (* 3 4)) (- 9 (* 2 2))) 6)
    

    Operators have no precedence, implied or otherwise, since they can't be mixed. The only exceptions are unary + and -, which simply indicate the sign of a number:

      (* 3 -1)
    

    Order of evaluation is specified entirely by parentheses, which are required around each operator and its operands: (+ a (* b c)) instead of (a + b * c).

    S-Expressions provide a simple and isolated environment in which Kermit's macro names can be used without the \m(...) escaping that is normally required. Given:

      define a 1
      define b 2
      define c 3
    

    Then:

      (+ \m(a) \m(b) \m(c))
    

    is equivalent to:

      (+ a b c)
    

    Within an S-Expression, as in other strictly numeric contexts (Section 8.2), any operand that starts with a letter is treated as a Kermit macro name. In this context, abbreviations are not accepted; variable names must be spelled out in full. Alphabetic case is not significant; "a" and "A" are the same variable, but both are different from "area".

    Of course, regular Kermit variables and functions can be used in S-Expressions in the normal ways:

      (* \v(math_pi) (^ \%r 2))             ; Area of a circle with radius \%r
      (+ \fjoin(&a))                        ; Sum of all elements of array \&a[]
    

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    9.2. Integer and Floating-Point-Arithmetic

    Normally, if all numbers in an S-Expression are integers, the result is an integer:

      (+ 1 1)                               ; Result is 2
      (/ 9 3)                               ; Result is 3
    

    If any of the operands is floating point, however, the result is also floating point:

      (+ 1 1.0)                             ; Result is 2.0
      (/ 9.0 3)                             ; Result is 3.0
    

    If all the operands are integers but the result has a fractional part, the result is floating point:

      (/ 10 3)                              ; Result is 3.333333333333333
    

    To force an integer result in such cases, use the TRUNCATE operator:

      (truncate (/ 10 3))                   ; Result is 3
    

    Similarly, to force a computation to occur in floating point, you can coerce one of its operands to FLOAT:

      (+ 1 (float 1))                       ; Result is 2.0
    

    The result is also floating point if the magnitude of any integer operand, intermediate result, or the result itself, is larger than the maximum for the underlying machine architecture:

      (^ 100 100)
    

    If the result is too large even for floating-point representation, "Infinity" is printed; if it is too small to be distinguished from 0, 0.0 is returned.

    Large numbers can be used and large results generated, but they are accurate only to the precision of the underlying machine. For example, the result of:

     (+ 111111111111111111111 222222222222222222222)
    

    should be 333333333333333333333, but 333333333333333300000.0 is produced instead if the machine is accurate to only about 16 decimal digits, even with coercion to floating-point. The order of magnitude is correct but the least significant digits are wrong. The imprecise nature of the result is indicated by the ".0" at the end. Contrast with:

     (+ 111111111 222222222)
    

    which produces an exact integer result.

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    9.3. How to Use S-Expressions

    S-Expressions may be given as commands to C-Kermit. Any command whose first character is "(" (left parenthesis) is interpreted as an S-Expression.

    If you enter an S-Expression at the C-Kermit> prompt, its result is printed:

      C-Kermit>(/ 10.0 3)
       3.333333333333333
      C-Kermit>
    

    If an S-Expression is executed within a macro or command file, its value is not printed. However, you can control the printing action with:

    SET SEXPRESSION ECHO { AUTO, ON, OFF }
    AUTO is the default, meaning print the value at top level only; ON means always print the value; OFF means never print it.

    In any case, the value of the most recent S-Expression (and the S-Expression itself) may be accessed programmatically through the following variables:

    \v(sexpression)
    The S-Expression most recently executed.

    \v(svalue)
    The value of the S-Expression most recently executed.

    Besides issuing S-Expressions as commands in themselves, you can also execute them anywhere within a Kermit command, but in this case they must be enclosed in a function call (otherwise they are taken literally):

    \fsexpression(s)
    The argument "s" is an S-Expression; the outer parentheses may be omitted. The value of the S-Expression is returned. Note that since S-Expressions usually contain spaces, some form of grouping or quoting might be needed in some contexts:

      echo \fsexpression((+ 1 1))            ; Outer parentheses may be included
      echo \fsexpr(+ 1 1)                    ; Outer parentheses may be omitted
      echo Value = "\fsexp(+ 1 a)"           ; Can be embedded in strings
      echo Value = \&a[\fsexp(/ b 2)]        ; Can be used in array subscripts
      if = {\fsexp(+ 1 1)} 2 {               ; Braces needed here for grouping
          echo One plus one still equals two
      }
    

    The IF statement illustrates how to use S-Expressions as (or in) IF or WHILE conditions:

    If an S-Expression is the last command executed in a macro, its value becomes the return value of the macro; no RETURN command is needed. Example:

      def newarea {
          (let s (/ (+ \%1 \%2 \%3) 2.0))
          (sqrt (* s (- s \%1) (- s \%2) (- s \%3)))
      }
    

    This is equivalent to (but more efficient than):

      def newarea {
          (let s (/ (+ \%1 \%2 \%3) 2.0))
          return \fsexp(sqrt (* s (- s \%1) (- s \%2) (- s \%3)))
      }
    

    When an S-Expression is entered as a command -- that is, the first nonblank character of the command is a left parenthesis -- then it is allowed to span multiple lines, as many as you like, until the first left parenthesis is matched:

      (let s (/
              (+
               \%1
               \%2
               \%3
               )
              2.0
              )
           )
      (sqrt (*
             s
             (- s \%1)
             (- s \%2)
             (- s \%3)
             )
            )
    

    The S-Expression concept lends itself easily to embedding and recursion, but the depth to which recursion can occur is limited by the resources of the computer (memory size, address space, swap space on disk) and other factors. There is no way that C-Kermit can know what this limit is, since it varies not only from computer to computer, but also from moment to moment. If resources are exhausted by recursion, C-Kermit simply crashes; there's no way to trap this error. However, you can set a depth limit on S-Expressions:

    SET SEXPRESSION DEPTH-LIMIT number
    Limits the number of times the S-Expression reader can invoke itself without returning to the given number. The default limit is 1000. This limit applies to S-Expressions embedded within other S-Expressions as well as to S-Expressions that invoke recursive macros. If the limit is exceeded, Kermit prints "?S-Expression depth limit exceeded" and returns to its prompt. More about recursion in Section 9.8.

    You can also test the depth programmatically:

    \v(sdepth)
    The current S-Expression invocation depth. The depth includes both nesting level and recursion. For example, in: (foo (foo (foo (foo (foo))))), the innermost (foo) is at depth 5.

    Help, completion, and syntax checking are not available within an S-Expression. If you type ? within an S-Expression, it says:

      C-Kermit>(? S-Expression ("help sexp" for details)
    

    As it says, typing "help sexp" will display a brief help text.

    The SHOW SEXPRESSION command displays current SET SEXPRESSION settings and related information.

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    9.4. Summary of Built-in Constants and Operators

    Three constants are built in:

    These constants are specific to S-Expressions and are not visible outside them. They may not be used as the target of an assignment. So, for example:

      (setq t 0)   Fails
      assign t 0   Succeeds but this is not the same T!
    

    E (the base of natural logarithms, 2.7182818184...) is not built in since it is not intrinsic in most Lisp dialects. If you want E to be the base of natural logarithms you can:

      (setq e (exp 1))
    

    Operators are either symbols (such as "+") or words. Words must be spelled out in full, not abbreviated. Differences of alphabetic case are ignored.

    The most basic operation in S-Expressions is evaluation:

    EVAL [ s-expression or variable or number [ another [ another ... ] ] ]
    Evaluates its operands and returns the value of the last one evaluated. Examples:

      (eval)                                0
      (eval 1)                              1
      (eval a)                              value of a
      (eval (+ 1 a))                        value of a+1
      (eval (setq a 1) (setq b (+ a 0.5)))  value of b (= a+0.5)
    

    You can use "." as a shorthand for EVAL:

      (.)
      (. 1)
      (. a)
      (. (+ 1 a))
      (. (setq a 1) (setq b (+ a 0.5)))
    

    Opposite of EVAL is the operator that suppresses evaluation of its operand:

    QUOTE item
    The value (quote item) is "item". If the item is itself an S-Expression, the result is the S-Expression with the outer parentheses stripped. Examples:

      (quote)                               (illegal)
      (quote a)                             a
      (quote hello)                         hello
      (quote (this is a string))            this is a string
      (quote this is a string)              (illegal)
    

    A shorthand notation is also accepted for quoting:
    'a is equivalent to (quote a). And therefore:
    '(a b c) is equivalent to (quote (a b c)).
    More about quoting in Section 9.8.

    STRING item
    Is a combination of EVAL and QUOTE. It evaluates the item as an S-Expression, and then puts quotes around the result (more about this in Section 9.8).

    The following operators assign values to variables:

    SETQ [ variable [ value [ variable [ value [ ... ] ] ] ] ]
    Applies to global variables. For each variable given: if a value is not given, the variable is undefined. If a value is given, assigns the value to the variable. The value may be a number, a variable, or anything that resolves to a number including an S-Expression. Returns the value of the last assignment. Examples:

      (setq)             Does nothing, returns NIL.
      (setq a)           Undefines a, returns NIL.
      (setq a 1)         Assigns 1 to a, returns 1.
      (setq a 1 b 2)     Assigns 1 to a, 2 to b, returns 2.
      (setq a 1 b 2 c)   Assigns 1 to a, 2 to b, undefines c, returns NIL.
    

    To undefine a variable that is not the final one in the list, give it a value of "()" or NIL:

      (setq a () b 2)    Undefines a, assigns 2 to b, returns 2.
      (setq a nil b 2)   Ditto.
    

    Note that a variable can be used right away once it has a value:

      (setq a 1 b a)     Assigns 1 to a, the value of a (1) to b, returns 1.
    

    The results of SETQ (when used with macro names) can be checked conveniently with SHOW MACRO, e.g:

      show mac a b c
    

    LET [ variable [ value [ variable [ value [ ... ] ] ] ] ]
    Like SETQ, but applies to local variables. Note that "local" is used in the Kermit sense, not the Lisp sense; it applies to the current Kermit command level, not to the current S-Expression.

    If you want to use SETQ or LET to assign a value to a backslash variable such as \%a or \&a[2], you must double the backslash:

      (setq \\%a 3)
      (setq \\%b (+ \%a 1))
      (setq \\&a[2] (setq (\\%c (+ \%a \%b))))
    

    In other words:

    See Section 9.6 for a fuller explanation of variable syntax and scope.

    Here's a summary table of arithmetic operators; in the examples, a is 2 and b is -1.3:

      Operator  Description                            Example           Result
      +         Adds all operands (0 or more)          (+ a b)           0.7
      -         Subtracts all operands (0 or more)     (- 9 5 2 1)       1
      *         Multiplies all operands (0 or more)    (* a (+ b 1) 3)  -1.80
      /         Divides all operands (2 or more)       (/ b a 2)        -0.325
      ^         Raise given number to given power      (^ 3 2)           9
      ++        Increments variables                   (++ a 1.2)        3.2
      --        Decrements variables                   (-- a)            1
      ABS       Absolute value of 1 operand            (abs (* a b 3))   7.8
      MAX       Maximum of all operands (1 or more)    (max 1 2 3 4)     4
      MIN       Minimum of all operands (1 or more)    (min 1 2 3 4)     1
      MOD (%)   Modulus of all operands (1 or more)    (mod 7 4 2)       1
      FLOAT     Convert an integer to floating-point   (float 1)         1.0
      TRUNCATE  Integer part of floating-point operand (truncate 3.333)  3
      CEILING   Ceiling of floating-point operand      (ceiling 1.25)    2
      FLOOR     Floor of floating-point operand        (floor 1.25)      1
      ROUND     Operand rounded to nearest integer     (round 1.75)      2
      SQRT      Square root of 1 operand               (sqrt 2)          1.414..
      EXP       e (2.71828..) to the given power       (exp -1)          0.367..
      SIN       Sine of angle-in-radians               (sin (/ pi 2))    1.0
      COS       Cosine of angle-in-radians             (cos pi)         -1.0
      TAN       Tangent of angle-in-radians            (tan pi)          0.0
      LOG       Natural log (base e) of given number   (log 2.7183)      1.000..
      LOG10     Log base 10 of given number            (log10 1000)      3.0
    

    The ++ and -- operators are also assignment operators and work just like SETQ and LET in their interpretations of operators and operands, but:

    If you include more than one variable-value pair in a ++ or -- expression, every variable (except, optionally, the last) must be followed by a value. Examples:

      (++ a)                Equivalent to (setq a (+ a 1)) and to (++ a 1)
      (++ a 2)              Equivalent to (setq a (+ a 2))
      (-- a (* 2 pi))       Equivalent to (setq a (- a (* 2 pi)))
      (++ a 1 b 1 c 1 d)    Equivalent to four SETQs incrementing a,b,c,d by 1.
    

    Another group of operators forms the predicates. These return a "truth value", in which 0 (or NIL) is false, and 1 or any other nonzero number is true.

      Operator  Description                            Example           Result
      = (or ==) Operands are equal                     (= 1 1.0)         1
      !=        Operands are not equal                 (!= 1 1.0)        0
      <         Operands in strictly ascending order   (< 1 2 3)         1
      <=        Operands in ascending order            (<= 1 1 2 3)      1
      >         Operands in strictly descending order  (> 3 2 1)         1
      >=        Operands in descending order           (<= 3 3 2 1)      1
      AND (&&)  Operands are all true                  (and 1 1 1 1 0)   0
      OR  (||)  At least one operand is true           (or 1 1 1 1 0)    1
      XOR       Logical Exclusive OR                   (xor 3 1)         0
      NOT (!)   Reverses truth value of operand        (not 3)           0
    

    The Exclusive OR of two values is true if one value is true and the other value is false.

    And another group operates on bits within an integer word:

      Operator  Description                            Example           Result
      &         Bitwise AND                            (& 7 2)           2
      |         Bitwise OR                             (| 1 2 3 4)       7
      #         Bitwise Exclusive OR                   (# 3 1)           2
      ~         Reverses all bits                      (~ 3)            -4
    

    These operators coerce their operands to integer by truncation if necessary. The result of bit reversal is hardware dependent.

    The final category of operator works on truth values:

      Operator  Description                            Example           Result
      IF        Conditional evaluation                 (if (1) 2 3)      2
    

    IF (predicate) (s1) [ (s2) ]
    The IF operator is similar to Kermit's IF command. If the predicate is true (i.e. evaluates to a nonzero number), the first S-Expression (s1) is evaluated and its value is returned. Otherwise, if (s2) is given, it is evaluated and its value returned; if (s2) is not given, nothing happens and the NIL (empty) value is returned.

    You can group multiple expressions in the s1 and s2 expressions using EVAL (or "."):

      (if (< a 0) (eval (setq x 0) (setq y 0)) (eval (setq x a) (setq y b)))
    

    or equivalently:

      (if (< a 0) (. (setq x 0) (setq y 0)) (. (setq x a) (setq y b)))
    

    Each operator has its own requirement as to number and type of operands. In the following table, "number" means any kind of number -- integer or floating-point -- or a variable, function, macro, or S-Expression that returns a number; "vname" means variable name, "fpnumber" means a floating-point number (or anything that resolves to one), and "integer" means integer (or anything that resolves to one). "truthvalue" means anything that resolves to a value of zero or an empty value (which indicates false) or a nonzero value (which indicates true). "any" means any kind of value, including none at all.

      Operator  Number of operands   Type of operands    Returns
      EVAL  (.) 0 or more            S-Expression        Last value (default NIL)
      STRING    1                    S-Expression        string
      QUOTE (') 1                    word                string
      SETQ      0 or more            vname value pairs   Last value (default NIL)
      LET       0 or more            vname value pairs   Last value (default NIL)
      +         0 or more            number              number     (default 0)
      -         0 or more            number              number     (default 0)
      *         0 or more            number              number     (see note (1))
      /         2 or more            number              number
      ^         2 or more            number              number
      ++        1 or more            vname value pairs   Result of last increment
      --        1 or more            vname value pairs   Result of last decrement
      ABS       1                    number              number
      MAX       1 or more            number              number
      MIN       1 or more            number              number
      MOD (%)   2                    number              number
      FLOAT     1                    number              fpnumber
      TRUNCATE  1                    number              integer
      CEILING   1                    number              integer
      FLOOR     1                    number              integer
      ROUND     1                    number              integer
      SQRT      1                    number              fpnumber
      EXP       1                    number              fpnumber
      SIN       1                    number              fpnumber
      COS       1                    number              fpnumber
      TAN       1                    number              fpnumber
      LOG       1                    number              fpnumber
      LOG10     1                    number              fpnumber
      = (==)    1 or more            number              truthvalue
      !=        1 or more            number              truthvalue
      <         1 or more            number              truthvalue
      <=        1 or more            number              truthvalue
      >         1 or more            number              truthvalue
      >=        1 or more            number              truthvalue
      AND (&&)  1 or more            truthvalue          truthvalue
      OR  (||)  1 or more            truthvalue          truthvalue
      XOR       2                    truthvalue          truthvalue
      NOT (!)   1                    truthvalue          truthvalue
      &         1 or more            number (see note 2) integer
      |         1 or more            number (see note 2) integer
      #         2                    number (see note 2) integer
      ~         1                    number (see note 2) integer
      IF        2 or 3               truthvalue,any,any  any
    

    Operators that don't require any arguments return the default values shown.

    1. The value of "*", when used as an operand, is initially "1" and the value of the most recent S-Expression thereafter, as in Franz Lisp. This is handy when doing a series of calculations by hand:

        C-Kermit>(* 13272.42 0.40)
         5308.968
        C-Kermit>(/ * 2)
         2654.4840
        C-Kermit>
      

    2. The bitwise operators coerce their operands to integer by truncation.

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    9.5. Variables

    As noted elsewhere in this discussion, all backslash items (variables such as \%a, macro parameters such as \%1, array elements such as \&a[\%i], built-in variables such as \v(ndate), built-in functions such as \fjoin(), macro names enclosed in \m(), \s(), or \:(), etc) are evaluated at "top level" before the S-Expression is sent to the S-Expression reader. To use a backslash variable as the target of an assignment (e.g. by SETQ, LET, ++, or --), you must double the backslash, e.g. (setq \\%r 1234). This is discussed at greater length in the next section.

    Thus S-Expression reader generally deals only with macro names (not backslash items) as variables. It is important to understand how the reader handles macro names. There are fundamentally two kinds of S-Expressions: those that contain a single element, such as:

      (foo)
    

    and those that contain more than one element:

      (foo a b c)
    

    If an S-Expression contains only one element, and it is the name of a macro, the macro's definition is examined. If the definition is a number (integer or floating-point, positive or negative), then this becomes the value of the expression. If the definition starts with ' (apostrophe), then the quoted word or string is the value of the expression (explained in Section 9.8). Otherwise, the macro is assumed to be composed of Kermit commands (possibly including S-Expressions), which are executed. If the macro has a RETURN value, or it executes an S-Expression as its last command, the result becomes the value of the S-Expression; otherwise the result is empty.

    For S-Expressions that contain more than one element, and the first element is the name of a macro, then this macro is executed with the arguments that are given, after the arguments are evaluated by the S-Expression reader. Likewise, If the first element is a built-in operator, then it is applied to the operands after they are evaluated. In both cases, each operand is fed to the S-Expression reader recursively for evaluation. If an operand is a number or a quoted string, it is used as-is. But if it's a macro name, this degenerates into the first case, and the previous paragraph applies.

    Examples:

      define foo 123
      (foo)                                Result: 123
      define foo 'abc
      (foo)                                Result: abc
      define foo '(one two three)
      (foo)                                Result: one two three
      define foo return \frandom(1000)
      (foo)                                Result: 713 (or other number)
      define foo (+ a b)
      (foo)                                Result: The sum of a and b
    

    A more difficult example:

      define foo abc
      (foo)                                Result: ???
    

    The result in the last example depends on the definition of abc:

    The use of macros as S-Expression operators is described in Section 9.8.

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    9.6. Assignments and Scope

    The assignment operators SETQ and LET apply to global and local variables, respectively. SETQ and LET are standard Lisp operators adapted to Kermit scoping rules. When the operands are numeric or arithmetic, SETQ is equivalent to Kermit's EVALUATE command:

      (setq a (+ 1 2))
      evaluate a 1 + 2
    

    When the operand is a string, SETQ is equivalent to DEFINE:

      (setq a '(this is a string))
      define a this is a string
    

    In the first case, both statements create a macro named "a" with a value of 3. But in neither case is the macro "a" necessarily global. If either of these commands executes in an environment (i.e. macro invocation level) where a "local a" command has been given, the "a" macro is global to that environment, but is not visible outside it.

    LET is equivalent to the Kermit LOCAL command, followed by the corresponding EVALUATE:

      (let a (+ 1 2))
    

    is equivalent to:

      local a
      evaluate a 1 + 2
    

    Again, "local" in this context applies to the Kermit macro invocation stack, not to the S-Expression nesting level. To illustrate, recall our "newarea" macro:

    def newarea {
        (let a \%1 b \%2 c \%3)
        (let s (/ (+ a b c) 2.0))
        (sqrt (* s (- s a) (- s b) (- s c)))
    }
    

    Because SETQ and LET expressions return a value, they can be placed within a larger S-Expression. In this case we can replace the first reference to the "s" variable by its defining expression:

    def newarea {
        (let a \%1 b \%2 c \%3)
        (sqrt (* (let s (/ (+ a b c) 2.0)) (- s a) (- s b) (- s c)))
    }
    

    This would not work if LET were local to the S-Expression, but it works nicely in the context of Kermit macros. The previous definition is equivalent to:

    def newarea {
        local a b c s
        (setq a \%1 b \%2 c \%3)
        (sqrt (* (setq s (/ (+ a b c) 2.0)) (- s a) (- s b) (- s c)))
    }
    

    In both cases, the variables a, b, c, and s are local to the "newarea" macro, and global within it.

    Multiple assignments can be handled in several ways. Here is the obvious way to initialize a series of variables to the same value:

      (setq a 0)
      (setq b 0)
      (setq c 0)
      (setq s 0)
    

    Here is a more compact and efficient way of doing the same thing:

      (setq a 0 b 0 c 0 s 0)
    

    However, in case the value was more complex, it's better to put only one copy of it in the S-Expression; in this case we rely on the fact that SETQ returns the value of its last assignment:

      (setq a (setq b (setq c (setq s (* x (^ y 2))))))
    

    Similarly, to set a series of variables to x, x+1, x+2, ...

      (setq c (+ (setq b (+ (setq a (+ (setq s x) 1)) 1)) 1))
    

    In the last example, you can see why "last" does not always correspond to "rightmost" (the leftmost variable "c" is assigned last).

    If you are working with backslash variables like \%a or array elements like \&a[1], remember two rules:

    1. Don't put spaces inside array brackets.
    2. You must double the backslash when using SETQ, LET, ++, or -- to assign a value to a backslash variable.

    Examples of assigning to a backslash variable:

      (setq x 1)
      (setq \\%a 0)
      (setq \\&a[x+1] 1)
      (++ \\%x)
      (-- \\&a[x+2])
    

    Examples of referring to a backslash variable's value:

      (setq a (+ \%a 1))
      (setq b (+ \%a \&a[1]))
      (++ a \%x)
      (-- b \&a[1])
    

    The special notation is required because all backslashed items (\%x variables, array elements, built-in \v(xxx) variables, and \fxxx() function invocations) are evaluated in a single pass BEFORE the S-Expression is executed; any other approach would result in unacceptable performance. So, for example, in:

      declare \&a[] = 1 2 3
      define \%x 4
      define \%y 0
      (setq \\%y (+ \%x \&a[1]))
    

    the S-Expression becomes:

      (setq \%y (+ 4 1))
    

    before it is sent to the S-Expression evaluator. If the backslash had not been doubled on the assignment target, the result would have been:

      (setq 0 (+ 4 1))
    

    which is illegal because you can't assign a value to a number. Conversely, if backslashes were doubled on right-hand-side values:

      (setq \\%y (+ \\%x \\&a[1])
    

    this too, would give an error (not numeric - "\%x").

    If you omit the double backslash in the assignment target, the result depends on whether the variable already has a value:

      (setq \%a (* 3 3))
    

    If \%a has a non-numeric single-word value, then this becomes the name of the variable that is assigned by SETQ. To illustrate:

      define \%a foo
      echo \%a
      foo
      (setq \%a (* 3 3))
      echo \%a
      foo
      show macro foo
      foo = 9
    

    If \%a has no value, a numeric value, or a multiword value, an "invalid assignment" error occurs.

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    9.7. Conditional Expressions

    The IF operator provides a compact form of decision-making within S-Expressions. An IF expression can stand wherever a number might stand, as long is it returns a number. Here's a quick way to obtain the average value of all the elements in an array that contains only numbers:

      (/ (+ \fjoin(&a)) (float \fdim(&a)))
    

    This results in a "Divide by zero" error if the array is empty. If you want to define the average value of an empty array to be 0 instead of getting an error, you can use IF to check the array size:

      (if \fdim(&a) (/ (+ \fjoin(&a)) (float \fdim(&a))) 0)
    

    or equivalently:

      (if (not \fdim(&a)) 0 (/ (+ \fjoin(&a)) (float \fdim(&a))))
    

    Of course, IF can fit anywhere else into an S-Expression:

      (setq a (+ b (if (< c 0) 0 c)))
    

    and the IF expression can be as complex as you like:

      (setq a (+ b (if (and (or (> x 0) (> y 0)) (< c 0) (> d 1) (!= e 0)) 1 0)))
    

    and the "then" and "else" parts can contain multiple S-Expressions enclosed within (EVAL ...):

      (if x (eval (...) (...) (...)) (eval (...) (...) (...)))
    

    AND and OR operators are guaranteed to "short circuit". If any operand of AND is false, none of the subsequent operands is evaluated; likewise, if an OR operand is true, no further operands are evaluated.

    Bear in mind that the S-Expression IF is not the same as Kermit IF; the condition is only allowed to be an S-Expression or a variable or number, not the whole list of possibilities you see when you type "if ?" at the C-Kermit> prompt. But keep reading...

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    9.8. Extensibility

    To extend the capabilities of S-Expressions, you can use Kermit macro names as operators, with the following limitations:

    And with the following enhancement:

      define bump (++ \%1)
    

    is equivalent to:

      define bump return \fsexpression(++ \%1)
    

    Here's an example in which we define a FIBONACCI operator that returns the nth element, n >= 0, of the Fibonacci series, 0 1 1 2 3 5 8 13 21 34 55, . . ., in which the first element is 0, the second is 1, and each subsequent element is the sum of the two before it. This series was devised by Leonardo Pisano, Filius Bonacci (Fibonacci for short) in 1202 to describe how fast rabbits can breed, and also forms the basis for the Golden Mean, the branching behavior of plants, the spiral of a nautilus shell, etc. (Thanks to Dat Thuc Nguyen for December 2003 corrections to this section!)

    We can write a FIBONACCI function as a macro easily with S-Expressions:

      define FIBONACCI {
        (if (== \%1 0) 0
            (if (== \%1 1) 1 (+ (fibonacci (- \%1 2)) (fibonacci (- \%1 1)))))
      }
    

    You can read this as:

    If the argument (\%1) is 0, return a result of 0; if it is 1, return 1; otherwise:
    return the sum of fibonacci(argument - 2) and fibonacci(argument - 1)

    Note that a RETURN statement is not needed, since S-Expressions automatically set the return value of their containing macros.

    For comparison, here's how it would be coded without S-Expressions:

      define FIBONACCI {
          if == \%1 0 {
              return 0
          } else if == \%1 1 {
              return 1
          } else {
              return \feval(\fexec(fibonacci \feval(\%1-2)) -
                   + \fexec(fibonacci \feval(\%1-1)))
          }
      }
    

    Now we can use the FIBONACCI function (whichever way you write it) just as if it were a built-in operator:

      (fibonacci 6)
    

    Or:

      (setq a 10)
      (fibonacci a)
    

    Within S-Expressions only (not outside them), S-Expressions themselves can be used as macro arguments:

      (setq a 2 b 4)
      (setq x (fibonacci (* a b )))
    

    The value of the S-Expression (in this case "8"), and not the S-Expression itself, is sent to the macro.

    Your macro is responsible for argument validation and error handling. A robust Fibonacci macro would be more like this:

      define FIBONACCI {
          if < \v(argc) 2 end 1 ?\%0: Missing argument
          if > \v(argc) 2 end 1 ?\%0: Too many arguments
          if not integer \%1 end 1 ?\%0: Integers only
          if < \%1 1 end 1 ?\%0: Argument out of range
          (if (== \%1 0) 0
    	 (if (== \%1 1) 1 (+ (fibonacci (- \%1 2)) (fibonacci (- \%1 1)))))
      }
    

    Recall that "END nonzero-number [ message ]" causes a macro invocation to fail. When the macro is the operator in an S-Expression, this makes the S-Expression fail too. Also note that our Fibonacci macro is just an illustration, not a practical example. Since it is recursive (calls itself), it won't work for large arguments because the call stack can exceed available memory. See Section 9.9.2 for a practical alternative.

    Kermit macros, when used as S-Expression operators, can do anything at all except initiate file transfers: they can print messages on the screen, read and write files, interact with the user, and so on. For example, here's a macro ASKME that asks you to enter a number, makes sure that you did, and then returns its value for use in the S-Expression:

      define ASKME {
          local \%n
          while true {
              ask \%n { Number: }
              if not def \%n continue
              if not numeric \%n {
                  echo Not numeric - "\%n"
                  continue
              }
              break
          }
          return \%n
      }
      (setq a (* 2 (askme))) ; Get number from user, double it, assign result to a.
    

    Here's a macro you can use to validate that a number is in a given range:

      define inrange {
          if != \v(argc) 4 end 1 ?\%0: Wrong number of arguments
          if ( < \%1 \%2 || > \%1 \%3 ) return 0
          return 1
      }
    

    The first argument is the number to be checked, the second is the minimum acceptable value, the third is the maximum. You can use this (for example) in IF conditions:

      define yes echo \%1 IS OK
      define no echo \%1 IS NOT OK
    
      (setq a -1 b 999)
      (if (inrange a 0 100) (yes a) (no a))
      (if (inrange b -1000 +1000) (yes b) (no b))
    

    This is just an illustration, of course; there's already a built-in operator to let you do range checking without help from macros:

      (if (<= 0 a 100) (yes a) (no a))
      (if (<= -1000 b +1000) (yes b) (no b))
    

    To send string parameters to a macro, some kind of quoting is required to tell the S-Expression parser to take a given "word" literally rather than replacing it by its value. For this we use the Lisp QUOTE operator:

      define length return \flength(\%1)
      (length (quote abcdefghijklmnopqrstuvwxyz))
      26
    

    This causes the string "abcdefghijklmnopqrstuvwxyz" to be sent literally to the LENGTH macro. Kermit, like Lisp, also offers a shortcut for QUOTE, that lets us quote a word by prefixing it with a single quote (') character, also called apostrophe (ASCII 39):

      (length 'abcdefghijklmnopqrstuvwxyz)
      26
    

    The two forms are equivalent.

    How the macro treats its arguments is up to the macro. In the example above, the argument is treated as a literal string. However, it can also be treated as a variable name:

      define string This is a string
      define length return \flength(\m(\%1))
      (length 'string)
      16
    

    Note the construct \m(\%1). This means "the value of the macro whose name is the value of \%1". The value of \%1 in this case is the word "string", and the value of the macro whose name is "string" is "This is a string".

    What if the macro takes multiple arguments, or a variable number of them? Here's a simple macro that prints a phrase that includes its arguments:

      define complain echo It's too \%*!
    

    (Recall that \%* means "all arguments".)

    It can be called in the traditional way:

      complain hot                       Result: "It's too hot!"
      complain cold and wet              Result: "It's too cold and wet!"
    

    Or from an S-Expression if you quote the arguments:

      (complain 'hot)                    Result: "It's too hot!"
      (complain 'cold 'and 'wet)         Result: "It's too cold and wet!"
    

    To group multiple words into a single argument, use parentheses:

      (complain (quote (cold and wet)))  Result: "It's too cold and wet!"
      (complain '(cold and wet))         Result: "It's too cold and wet!"
    

    Note the difference:

      (complain 'cold 'and 'wet)         Three arguments
      (complain '(cold and wet))         One argument
    

    Since the COMPLAIN macro uses \%* to refer to all its arguments, no matter how many, it doesn't care which form you use. But it makes a difference in cases where the macro refers to its arguments individually.

    To illustrate, let's consider a macro that receives the name of a macro and its argument list and executes it with its arguments, without knowing how many arguments there are. The following LOOP macro is used to execute the given macro with the given argument list the requested number of times:

      def loop { local i, for i 1 \%1 1 do \%2 \%3 }
    

    Within the LOOP macro, the first argument (\%1) is the loop count, \%2 is the macro name, and \%3 is the argument list. When the LOOP macro is invoked traditionally like this:

      loop 3 complain hot
    

    it prints "It's too hot!" three times. To invoke it from an S-Expression, you must quote both the macro name as well as the argument, since in this case the macro name itself is an argument:

      (loop 3 'complain 'hot)
    

    Now what if you need to send different or variable numbers of arguments to the LOOP macro? The LOOP macro can handle it already, provided you group the arguments into LOOP's third argument (\%3). In Kermit syntax, without grouping:

      loop 3 complain cold and wet
    

    prints "It's too cold!" three times ("and wet" is lost); but with grouping (either of the following two forms):

      loop 3 complain {cold and wet}
      loop 3 complain "cold and wet"
    

    the LOOP macro prints "It's too cold and wet!" three times as desired.

    To do the same thing in an S-Expression, just use the Lisp forms of quoting instead of the Kermit forms; the following two are equivalent:

      (loop 3 'complain (quote (cold and wet)))
      (loop 3 'complain '(cold and wet))
    

    Here's a similar example in which we write a macro that shows both the name and the value of one or more other macros, whose names are given as arguments (similar to "show macro"):

      define display {
          local \%i
          for \%i 1 \v(argc)-1 1 {
              echo \&_[\%i] = \m(\&_[\%i])
          }
      }
    

    (Recall that \&_[] is the macro's argument vector array, equivalent to \%1, \%2, ...) The DISPLAY macro can be used in S-Expressions like this:

      (setq a 1 b 2 c 3)
      (display 'a 'b 'c 'd)
    

    which prints:

      a = 1
      b = 2
      c = 3
      d =
    

    The names must be quoted to prevent their evaluation before they are sent to the macro. This ability to pass variables "by name" to macros, rather than by value, lets you write macros that change the values of argument variables. For example, here's a macro that doubles the value of its argument variable:

      define double (++ \%1 \%1)
    

    which you can call like this:

      (setq a 12)
      (double 'a)
    

    In the macro, \%1 is replace by the variable name "a"; "(++ a a)" adds "a" to itself, and sets the value of "a" to the result.

    There are no built-in operators other than QUOTE, ', and STRING for handling strings in S-Expressions, but using just these, plus macros that use Kermit's regular string-handling features, you can easily extend S-Expressions to do string manipulation:

      define len return \flen(\%1)               Returns length of argument string
      define cap return \fupper(\%1)             Uppercase argument string
      define rev return \freverse(\%1)           Reverses argument string
      define sub return \fsubstr(\%1,\%2,\%3)    Returns substring of arg string
    
      (len '(this is a string))                  Result: 16
      (rev '(this is a string))                  Result: gnirts a si siht
      (rev (cap '(this is a string)))            Result: GNIRTS A SI SIHT
      (sub (rev (cap '(this is a string))) 5 9)  Result: TS A SI S
    

    You can assign a string to a macro name as follows:

      (setq foo '(this is a string))
      (setq foo (quote (this is a string)))
    

    The two are exactly equivalent. In both cases, the macro "foo" has the value:

      '(this is a string)
    

    so when it is retrieved it can be identified as a string rather than a number or commands to be executed. Thus:

      (setq foo (quote (this is a string)))
      show macro foo
      foo = '(this is a string)
      (foo)
      this is a string
    

    Note the different results for "show macro foo" and "(foo)". The former shows the internal definition; the latter evaluates the variable, which removes the quoting. And perhaps more important, note that if the apostrophe and surrounding parentheses were not stored as part of the definition, (foo) would try to execute "this is a string" as a command.

    Given the assignment above, the following work as expected:

      (len foo)                                  Result: 16
      (rev foo)                                  Result: gnirts a si siht
      (rev (cap foo))                            Result: GNIRTS A SI SIHT
      (sub (rev (cap foo)) 5 8)                  Result: TS A SI S
    

    Note that, unlike built-in S-Expression operators that return numbers or truth values, these operators return strings. If you want to assign their return values to other variables, you can do so:

      (setq bar (rev (cap foo)))                 Result: GNIRTS A SI SIHT
    

    But now the S-Expression processor doesn't know the value of "bar" is supposed to be a string, rather than a macro to execute. For this you need one final special operator, STRING. The STRING operator takes an S-Expression as an operand, evaluates it, and then returns its value enclosed in '(), so you can use the value as a string is subsequent S-Expressions. Use STRING for referencing macros that return strings:

      (setq bar (string (rev (cap foo))))        Result: '(GNIRTS A SI SIHT)
    

    STRING is like QUOTE, except that it evaluates its operand before applying the quoting, rather than taking the operand literally.

    To reference backslash variables or functions that return string values, you must use the regular quoting mechanisms:

      (setq time '(\v(time)))
      (setq date '(\v(date)))
      assign \%r this is a string
      (setq s1 '(\%r))
    

    That's because backslash items are evaluated BEFORE the S-Expression parser ever sees them, and the values of \v(time) and so on are not valid S-Expressions, so STRING won't like them.

    Finally a brief word on the touchy topic of quoting. Suppose you want to include (say) literal parentheses in a string that will later be processed by the S-Expression reader (or \fsplit() or \fword()). Normally, you can't do this because parentheses are meaningful in these contexts. To defeat the normal parsing rules, you can quote the parentheses with backslash. However, due to the many levels of string processing involved, a surprisingly large amount of backslashes might be required, for example:

      (setq s '(a b (c d) \\\\\\\\\\\\\\\\(e f (g h) x\\\\\\\\\\\\\\\\) j k))
    

    This is nearly impossible to explain(*). Instead, just remember two points:

    Considerations like this apply in any scripting language (shell, Tcl, Perl, Python, etc). The situation is known as "Quoting Hell".

    (*) If you really want an explanation, here it is:

    Moral: To create string constants in which grouping characters must be quoted, use DEFINE rather than SETQ.

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    9.9. Examples

    9.9.1. Statistics

    The following program computes statistics -- means, maxima, minima, variance, standard deviation, and correlation -- from data stored in parallel arrays, \&x[] and \&y[], which can contain any mixture of integer and floating-point numbers: positive, negative, or zero. Array setup and validation are not shown. Except for the traditional FOR loop and printing the results at the end, the entire computation is done with S-Expressions:

    ; Initialize sums, maxima, minima, and number of elements
    
      (setq xsum 0 ysum 0 xsum2 0 ysum2 0 xysum 0)
      (setq xmin (setq xmax \&x[1]) ymin (setq ymax \&y[1]))
      (setq n \fdim(&x))
    
    ; Loop through elements and accumulate sums, maxima, and minima
    
      for i 1 n 1 {
          (setq x \&x[i] y \&y[i])                    ; Notational convenience
          (setq xmax (max xmax x) ymax (max ymax y))  ; X and Y maxima
          (setq xmin (min xmin x) ymin (min ymin y))  ; X and Y minima
          (++ xsum x ysum y)                          ; X and Y sums
          (++ xsum2 (^ x 2) ysum2 (^ y 2))            ; Sum of X and Y squares
          (++ xysum (* x y))                          ; Sum of XY products
      }
    
    ; Calculate results
    
      (setq xmean (/ xsum n) ymean (/ ysum n))        ; Mean X and Y
      (setq xss (- xsum2 (/ (^ xsum 2) n)))           ; Intermediate values
      (setq yss (- ysum2 (/ (^ ysum 2) n)))
      (setq xyss (- xysum (/ (* xsum ysum) n)))
      (setq xvar (/ xss n) yvar (/ yss n))            ; X and Y variance
      (setq sdx (sqrt xvar) sdy (sqrt yvar))          ; Std deviation in X and Y
      (setq tmp (* xss yss))
      (setq cc (if tmp (/ xyss (sqrt tmp)) 1.0))      ; Correlation coefficient
      show macro xmean ymean xvar yvar sdx sdy cc     ; Print the results
    

    The final "if tmp" check accounts for the possibility that both arrays contain all 0's. Results can also be printed with "echo CC = \m(cc)", or any other desired way. Interestingly, if we had not needed the sum of the squares and products, we could have obtained the sums, maxima, and minima of the X's and Y's without a loop like this:

      (setq xsum (+ \fjoin(&x)) ysum (+ \fjoin(&y)))
      (setq xmax (max \fjoin(&x)) ymax (max \fjoin(&y)))
      (setq xmin (min \fjoin(&x)) ymin (min \fjoin(&y)))
    

    Any Kermit function that returns numbers or lists of numbers can be included in an S-Expression as an operand.

    9.9.2. Practical Fibonacci Series

    The recursive Fibonacci example given previously is simple and elegant, but not very useful since it causes memory occupation to grow each time it calls itself, until eventually both physical memory and disk swap space are filled and the program crashes. Even for small arguments, like 17, execution time can be prohibitive:

      (setq t1 \v(ftime))
      (setq result (fibonacci 17))
      (setq t2 (- \v(ftime) t1))
      echo FIBONACCI(17) = \m(result): TIME = \ffpround(t2,3)
    

    prints (on a certain rather slow computer):

      FIBONACCI(17) = 1597: TIME = 5.861
    

    Any recursive function can be recoded iteratively. The result is not as pretty, but execution is far less expensive:

        define FIBITER {
    	(if (== \%3 0) (\%2) (fibiter (+ \%1 \%2) \%1 (- \%3 1)))
        }
        define FIBONACCI {
            (fibiter 1 0 \%1)
        }
    

    Here's the result on the same computer for the same argument of 17:

      FIBONACCI(17) = 1597: TIME = 0.015
    

    (47 times faster.) Execution time increases proportionally to the size of the argument in the iterative case, whereas in the recursive case it goes up geometrically, quickly reaching infinity.

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    9.10. Differences from Algebraic Notation

    In C-Kermit:

    [ Top ] [ Contents ] [ C-Kermit Home ] [ Kermit Home ]

    9.11. Differences from Lisp

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    10. FILE TRANSFER

    New commands and switches:

    SET TRANSFER REPORT { OFF, ON }
    Enables or disables the (new) one-line message printed by Kermit after a remote-mode file transfer to indicate the source and destination file, complete with path, to let you know where the file went.

    SEND /TYPE:{TEXT,BINARY}
    Sends only files of the given type (see Section 4).

    SEND /NOFOLLOWLINKS:
    (UNIX only) Skip over symbolic links rather than following them (default). This applies to wildcard and/or recursive SENDs; if a single filename is given, and it happens to be a symbolic link, the file it points to is sent.

    SEND /FOLLOWLINKS:
    (UNIX only) Follow (resolve) symbolic links. Watch out for circular links, endless loops, etc.

    SET SEND I-PACKETS { OFF, ON }
    When sending commands to a Kermit server, this tells whether command packets should be preceded by an I (information) packet, which is used to synchronize parameters prior to executing the command. Normally ON. The only reason to set this OFF is for communicating with buggy Kermit servers that misbehave when an I packet is sent to them. There is also a SET RECEIVE I-PACKETS command, but presently it has no effect.

    SET TRANSFER MESSAGE [ text ]
    Sets an initial message to be shown in the Last Message field of the fullscreen file-transfer display.

    SET TRANSFER TRANSLATION { ON, OFF }
    Inhibits or re-enables text-file transfer character-set translation globally.

    { SEND, MSEND, GET, RECEIVE } /TRANSPARENT
    Inhibits character-set translation for this transfer only.

    { GET, RECEIVE } /PIPES:{ON,OFF}
    Overrides global TRANSFER PIPES setting for this transfer only; ON allows incoming files with names like "!tar xf -" to be opened as pipelines rather than regular files.

    The following new "hot keys" are available when Kermit's file-transfer display is visible:

      D: Turn on debugging, open "debug.log" if not already open.
      d: Turn off debugging but leave log open (if it was open).
      T: Turn on debug-log timestamps.
      t: Turn off debug-log timestamps.

    Other improvements:

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    11. MODEMS AND DIALING

    In C-Kermit 8.0, the default modem type for dialing has changed from NONE (= DIRECT, meaning no modem) to GENERIC. This change should have no impact on direct connections. For dialing, it means that, unless you SET MODEM TYPE to a specific type, such as USROBOTICS or CONEXANT, Kermit assumes:

    1. The modem uses the Hayes AT command set.
    2. The modem supports error correction, data compression, and hardware flow control and is already configured to use them.

    In fact, Kermit assumes the modem is completely configured, and therefore does not send it an initialization string or any configuration commands. Instead, it sends only the simplest and most portable commands:

      ATQ0V1          Give dial result codes.
      ATDTnumber      Dial the number.

    (or ATD or ATDP, as appropriate).

    The new defaults work for direct connections and for most modern modems on most platforms, and they work much faster than "full-treatment" dialing. If the new defaults don't work for you, or if you need to perform explicit modem configurations or interactions, then set a specific modem type and use the SET MODEM and SET DIAL commands as documented in Using C-Kermit.

    WARNING: Don't use the generic modem on hosts that do not support RTS/CTS flow control. If Xon/Xoff is in use on the serial port, you'll need to select a particular modem type so Kermit knows what command to give it to enable Xon/Xoff flow control between itself and your serial port.

    The following new modem types were added in C-Kermit 8.0:

      lucent:          Lucent Venus chipset
      pctel:           PCTel V.90 chipset
      conexant:        Conexant (ex-Rockwell) modem family
      zoom-v32bis:     New name for "Zoom"
      zoom-v34         Zoom V.34
      zoom-v90         Zoom V.90 56K
      zoom-v92:        Zoom V.92 with V.44 data compression
      zoltrix-v34:     New name for "zoltrix"
      zoltrix-hsp-v90: Synonym for PCTel
      zoltrix-hcf-v90: Synonym for ITU-T-V250
      smartlink-v90:   Synonym for usrobotics (same chipset)
      acer-v90:        Synonym for Rockwell-v90

    New DIAL-related variables:

      \v(dm_hf):  Dial modifier: Wait for Hook-Flash.
      \v(dm_wb):  Dial modifier: Wait for Bong.

    Finally, if dialing fails, Kermit now prints a context-sensitive hint suggesting possible reasons and remedies.

    Added in C-Kermit 8.0.201:   Rudimentary support for Caller ID, for use with the ANSWER command. If the modem reports Caller ID information, Kermit stores it in variables that you can access after the call is answered:

      \v(callid_date)   The date of the call
      \v(callid_time)   The time of the call
      \v(callid_name)   The name of the caller
      \v(callid_nmbr)   The telephone number of the caller
      \v(callid_mesg)   A message
    

    The format of these items depends on the originating and answering phone companies and the modems and their configuration.

    Not very many modems support Caller ID, and those that do (a) tend to have it disabled by default, and (b) use different commands to enable it. A quick survey shows of some current models shows:

       - USR V.90:      No
       - ITU-T V.250:   No
       - Lucent Venus:  No
       - Diamond Supra: #CID=1
       - Rockwell 56K:  #CID=1
       - PCTEL:         #CID=1
       - Zoltrix:       +VCID=1
       - Conexant:      +VCID=1
    

    To use Kermit's Caller ID feature, you have to set the modem to wait for at least two rings before answering, and you have to give the command to enable Caller ID; for example (after choosing a modem with SET MODEM TYPE):

      set modem command autoanswer on ATS0=2#CID=1\{13}
      set modem command autoanswer on ATS0=2+VCID=1\{13}
    

    These commands can be undone with:

      set modem command autoanswer on ATS0=1#CID=0\{13}
      set modem command autoanswer on ATS0=1+VCID=0\{13}
    

    Kermit presently has no built-in knowledge of the Caller ID capabilities or commands of the modems in its database.

    Since the variables can be accessed only after the call is answered, the only way to refuse a call is to answer it, inspect the variables, and then hang it up if desired.

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    12. TERMINAL CONNECTION

    Now that 7-bit connections are no longer the norm, the default terminal bytesize (also called "data size" or "word size") in C-Kermit 8.0 is 8 bits, rather than 7 bits as it was in C-Kermit 7.0 and earlier:

    SET ESCAPE character
    This command, which specifies your CONNECT-mode escape character, allows you to specify any ASCII control character in a variety of formats. C-Kermit 8.0.201 now also lets you specify any 8-bit value, 128-255, as the escape character. In the SET ESCAPE command, you can type the 8-bit character literally or you can enter its numeric code. Here are examples that you can enter from a terminal or console that uses the ISO Latin-1 character set:

      C-Kermit> set escape Ã
      C-Kermit> set escape 195
      C-Kermit> show escape
       Escape character: Code 195 (Ã): enabled
      C-Kermit>
    

    Both of these commands set the escape character value to 195 (decimal), which happens to be uppercase letter A with Tilde in Latin-1. SHOW ESCAPE and SHOW TERMINAL show the value, as does the CONNECT message.

    SET TERMINAL AUTODOWNLOAD ERROR { STOP, CONTINUE }
    When Kermit has a terminal connection to another computer, and a file transfer is initiated automatically because a Kermit packet was received in CONNECT mode (i.e. in the terminal screen), this command tells what Kermit should do if the transfer fails. The default is to STOP, which leaves Kermit in command mode with its file-transfer display showing, so you can see that the transfer failed and why. If you SET TERMINAL AUTODOWNLOAD ERROR CONTINUE, this causes Kermit to return automatically to its terminal screen (i.e. resume its CONNECT session) as if the transfer had succeeded; this can be desirable if the entire session is under control of a host-based script.

    SET TERMINAL BYTESIZE { 7, 8 }
    The byte size to use during CONNECT and INPUT command execution, which can be more restrictive than the bytesize implied by the current PARITY setting, but not less restrictive. In C-Kermit 7.0 and earlier, the terminal bytesize was 7 by default to protect against the likelihood that parity was in use on the connection without the user's knowledge. When the terminal bytesize is 8 (as it is in C-Kermit 8.0 and later), the user will see garbage in this (increasingly unlikely) situation. Note that 8 data bits are required for most character sets other than ASCII: Latin-1, UTF-8, and so on.

    A new command has been added to produce timestamped session logs:

    SET TERMINAL SESSION-LOG TIMESTAMPED-TEXT
    Records the terminal session in text mode (like SET TERMINAL SESSION-LOG TEXT) but adds a timestamp at the beginning of each line. The timestamp format is hh:mm:ss.nnn, and indicates the time at which the first character of the line appeared.

    In most UNIX versions (those built with the select()-capable CONNECT module -- pretty much all the ones that have or could have TELNET included), an idle timeout feature has been added:

    SET TERMINAL IDLE-TIMEOUT number
    If the number is not 0, then Kermit is to take an action when the given amount of time passes with no activity during CONNECT mode. If the number is positive it is the maximum number of idle seconds; if number is negative it represents milliseconds (thousandths of seconds). If 0 is given as the number, there are no idle timeouts. Synonym: SET TERMINAL IDLE-LIMIT.

    SET TERMINAL IDLE-ACTION { RETURN, HANGUP, EXIT, OUTPUT [ string ] }
    The action to be taken upon an idle timeout in CONNECT mode. RETURN to the prompt, HANGUP the connection, EXIT from Kermit, or OUTPUT the given string (if no string is given, a NUL (ASCII 0) character is sent).

    SET TERMINAL IDLE-ACTION { TELNET-NOP, TELNET-AYT }
    Actions that can be selected on Telnet connections only, that might be useful if idle limits are enforced by the Telnet server or in the TCP/IP protocol: TELNET-NOP sends a "NO Operation" (do-nothing) command, which causes no response from the server; TELNET-AYT sends an "Are You There" message to the server, which should make the server send back a message. Neither of these actions interferes with your remote session.

    SET TERMINAL IDLE-ACTION is useful for connections to hosts or services that automatically log you out after a certain amount of idle time, e.g.:

      set term idle-timeout 300
      set term idle-action output \32
    

    sends a space (as if you had pressed the space bar) every 300 seconds (five minutes) while there is no activity (32 is the ASCII code for space).

    When C-Kermit returns from CONNECT to command mode, the reason for the transition is given in a new variable, \v(cx_status):

       0  No CONNECT command given yet.
       1  User escaped back manually.
       2  A trigger string was encountered.
       3  IKSD entered server mode.
       4  Application Program Command received from host.
       5  Idle timeout.
       6  Telnet protocol error.
       7  Keystroke macro.
       8  Time limit exceeded.
     100  Internal error.
     101  Carrier required by not detected.
     102  I/O error on connection.
     103  Disconnected by host.
     104  Disconnected by user.
     105  Session limit exceeded.
     106  Rejected due to Telnet policy.
     107  Received kill signal.

    Values 100 and above indicate there is no connection.

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    13. CHARACTER SETS

    See the section on file scanning above, and the section on character-set conversion in FTP. Also:

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    14. DIALOUT FROM TELNET TERMINAL SERVERS

    For years, C-Kermit has supported dialing out from Telnet modem servers (also called reverse terminal servers or access servers), but until now there was no way for Kermit to control the communication parameters (speed, parity, etc) on the serial port of the terminal server; it had to use whatever was there.

    But now, if you make a connection to a server that supports the Telnet Com Port Control Option, RFC 2217, you have the same degree of control as you would have over a serial port on the computer where Kermit is running: SET SPEED, SET FLOW, SET PARITY, SET STOP-BITS, SHOW COMM, WAIT, SET CARRIER-WATCH, the modem-signal variables, sending Break, and so on, apply to the connection between the terminal server and the modem.

    For example, using a Cisco Access Server 2509, where specifying a TCP port in the 6000's selects a serial port that can be used for dialing out:

      set host xxx 6001      ; xxx is the IP hostname or address of the server
      (log in if necessary)  ; With a script or by hand
      set modem type usr     ; Tell Kermit what kind of modem it has
      set speed 57600        ; This affects the server's port
      set flow rts/cts       ; Ditto
      dial 7654321
    

    The modem server might or might not require a login sequence. It might also allow for automatic authentication, e.g. via Kerberos tickets. NOTE: If the modem server requires a login sequence, then REDIAL might not work as expected.

    When you have a Telnet Com Port connection, your SET SPEED and SET FLOW options change automatically to reflect the capabilities of the server, rather than those of your local computer.

    See the configuration manual for your server for additional information. For example, how to set up the server to drop the Telnet connection automatically when the telephone call is hung up (e.g. "autohangup" on Cisco models).

    For a Linux-based Telnet Com-Port server, click the Sredird link:

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    15. COPING WITH BROKEN KERMIT PARTNERS

    There are lots of faulty Kermit protocol implementations out there, found mainly in 3rd-party products ranging from communications software packages to file-transfer functions embedded within devices. This topic is covered HERE for C-Kermit 7.0, but C-Kermit 8.0 adds some additional tricks.

    SET ATTRIBUTE RECORD-FORMAT { ON, OFF }
    Allows control of the Kermit's Record-Format attribute. Set this to OFF in case incoming file are refused due to unknown or invalid record formats if you want to accept the file anyway.

    SET ATTRIBUTES OFF
    This is not a new trick, but it was recently discovered that the Kermit implementation embedded within a certain kind of punching/bending machine (Salvagnini if you must know) hangs upon reception of standard format Kermit attributes when receiving files. When sending files, it sends attributes of its own, one per A-packet, which is slightly unusual but legal. When receiving files from C-Kermit, K95, MS-DOS Kermit, Kermit-370, etc, it simply exits upon reception of the first A-packet; apparently it was not coded according to the protocol specification, which allows multiple attributes per A-packet. Solution: tell the file sender to SET ATTRIBUTES OFF.

    SET SEND I-PACKETS { ON, OFF }
    A Kermit server is supposed to accept I-packets; this is how the client lets the server know its capabilities and preferences before sending a command. Apparently there is at least one Kermit server implementation that does not accept I-packets, and does not properly respond with an Error packet if it gets one. To get around such situations in C-Kermit 8.0, you can use SET SEND I-PACKETS OFF to inhibit the sending of I packets. In this case, the client must be able to adjust to the server's configuration, rather than the other way around as we are used to.

    SET PROTOCOL KERMIT {} {} {}
    C-Kermit 6.0 and later automatically send "autoupload" and "autodownload" commands when in local mode and you give a file transfer command. For example, if you tell kermit to "send oofa.txt", Kermit sends "kermit -r" and a carriage return, in case you had forgotten to start Kermit on the far end and told it to receive a file. If a Kermit program had already been started on the far end, it should harmlessly absorb this string. However, some Kermit programs violate the Kermit protocol definition and treat such strings as Kermit packets even though they are not. In such cases, give this command to set the Kermit protocol autoupload and download strings to nothing, which tells Kermit not to send them. (This is not a new feature, but it was not previously included in the "Coping" section of the documentation.)

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    16. NEW COMMAND-LINE OPTIONS

    kermit -h Now prints a complete listing of its command-line options, rather than an abbreviated list squeezed into a 24x80 space.

    -dd              Debug, like -d but adds timestamps
    --version  Shows C-Kermit version number.
    --noperms  Equivalent to SET ATTRIBUTE PROTECTION OFF.

    Kermit now accepts a selection of URLs (Universal Resource Locators) as its first command-line argument. These are:

    telnet:hostname
    Makes a Telnet connection to the given host (IP hostname or address).

    ftp://[user[:password]@]hostname[/path...]
    Makes an FTP connection to the given host (IP hostname or address). If a username is given, Kermit tries to log you in; if a password is given, it is used; if not, you are prompted for one. If no username is given, an anonymous login is performed. If a pathname is included, Kermit tries to GET the given file. See Section 3.1.3 for details.

    ftps://[user[:password]@]hostname[/path...]
    Makes a secure FTP connection over SSL.

    telnets://[user[:password]@]hostname
    Makes a secure Telnet connection over SSL.

    kermit://[user[:password]@]hostname[/path...]
    Makes a connection to an Internet Kermit Server.

    http://[user[:password]@]hostname[/path...]
    Makes a connection to Web server.

    https://[user[:password]@]hostname[/path...]
    Makes a connection to secure Web server.

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    17. LOGS

    In C-Kermit 8.0, we make an effort to keep passwords out of the debug log. This can never be 100% effective, but it's better than before, when there were no precautions at all. Whenever Kermit knows it's prompting for, parsing, or transmitting a password, it temporarily turns off logging and then turns it back on afterwards. This keeps the debug log password-free in most common cases, but there can be no guarantees.

    As noted elsewhere, the new "-dd" command-line option selects a timestamped debug log (equivalent to "set debug timestamps on", "log debug debug.log").

    C-Kermit 8.0 also supports a new timestamped session log via "set session-log timestamped-text", "log session".

    There have been requests for other kinds of logs, for example a command log. These might be added at some point. One person wanted to be able to log commands with timestamps, but only commands issued at the prompt, not commands from files or macros, and also wanted a header line at the beginning showing the date, user, and host. This can be done as follows:

      .filename := \v(home)commands.log  ; (for example)
      fopen /write \%c \m(filename)
      if success {
          fwrite /line \%c \v(date): User=\v(user) Host=\v(host)
          fclose \%c
          set debug timestamps on
          log debug {| grep "CMD(P)" >> \m(filename)} append
      }
    

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    C-Kermit 8.0 Update Notes / The Kermit Project / 15 Dec 2003 - 13 Sep 2010