C-Kermit on Open Kermit Project

C-Kermit Help Reference

Mon, 01 Jan 0001 00:00:00 +0000

C-Kermit Help Reference

Generated from a running kermit build by tools/gen_help_reference.py. Do not edit by hand.

Introductory Material

INTRO

Welcome to UNIX C-Kermit communications software for:
 . Error-free and efficient file transfer
 . Terminal connection
 . Script programming
 . International character set conversion
 . Numeric and alphanumeric paging
 
Supporting:
 . Serial connections, direct or dialed.
 . Automatic modem dialing
 . TCP/IP network connections:
   - Telnet sessions
   - SSH connections via external agent
   - Rlogin sessions
   - FTP sessions
   - HTTP 1.1 sessions
   - Internet Kermit Service
 
While typing commands, you may use the following special characters:
 . DEL, RUBOUT, BACKSPACE, CTRL-H: Delete the most recent character typed.
 . CTRL-W:      Delete the most recent word typed.
 . CTRL-U:      Delete the current line.
 . CTRL-R:      Redisplay the current line.
 . CTRL-P:      Command recall - go backwards in command recall buffer.
 . CTRL-B:      Command recall - same as Ctrl-P.
 . CTRL-N:      Command recall - go forward in command recall buffer.
 . CTRL-K:      Insert the most recently entered local file specifiction.
 . ?            (question mark) Display a menu for the current command field.
 . ESC          (or TAB or Ctrl-I) Attempt to complete the current field.
 . \            (backslash) include the following character literally
                or introduce a backslash code, variable, or function.
 
IMPORTANT: Since backslash (\) is Kermit's command-line escape character,
you must enter DOS, Windows, or OS/2 pathnames using either forward slash (/)
or double backslash (\\) as the directory separator in most contexts.
Examples: C:/TMP/README.TXT, C:\\TMP\\README.TXT.
 
Command words other than filenames can be abbreviated in most contexts.
 
Basic commands:
  EXIT          Exit from Kermit
  HELP          Request general help
  HELP command  Request help about the given command
  TAKE          Execute commands from a file
  TYPE          Display a file on your screen
  ORIENTATION   Explains directory structure
 
Commands for file transfer:
  SEND          Send files
  RECEIVE       Receive files
  GET           Get files from a Kermit server
  RESEND        Recover an interrupted send
  REGET         Recover an interrupted get from a server
  SERVER        Be a Kermit server
 
File-transfer speed selection:
  FAST          Use fast settings -- THIS IS THE DEFAULT
  CAUTIOUS      Use slower, more cautious settings
  ROBUST        Use extremely slow and cautious settings
 
File-transfer performance fine tuning:
  SET RECEIVE PACKET-LENGTH  Kermit packet size
  SET WINDOW                 Number of sliding window slots
  SET PREFIXING              Amount of control-character prefixing
 
To make a direct serial connection:
  SET LINE      Select serial communication device
  SET SPEED     Select communication speed
  SET PARITY    Communications parity (if necessary)
  SET FLOW      Communications flow control, such as RTS/CTS
  CONNECT       Begin terminal connection
 
To dial out with a modem:
  SET DIAL DIRECTORY     Specify dialing directory file (optional)
  SET DIAL COUNTRY-CODE  Country you are dialing from (*)
  SET DIAL AREA-CODE     Area-code you are dialing from (*)
  LOOKUP                 Lookup entries in your dialing directory (*)
  SET MODEM TYPE         Select modem type
  SET LINE               Select serial communication device
  SET SPEED              Select communication speed
  SET PARITY             Communications parity (if necessary)
  DIAL                   Dial the phone number
  CONNECT                Begin terminal connection
 
Further info:   HELP DIAL, HELP SET MODEM, HELP SET LINE, HELP SET DIAL
(*) (For use with optional dialing directory)
 
To make a network connection:
  SET NETWORK DIRECTORY  Specify a network services directory (optional)
  LOOKUP                 Lookup entries in your network directory
  SET NETWORK TYPE       Select network type (if more than one available)
  SET HOST               Make a network connection but stay in command mode
  CONNECT                Begin terminal connection
  TELNET                 Select a Telnet host and CONNECT to it
  RLOGIN                 Select an Rlogin host and CONNECT to it
  SSH [ OPEN ]           Select an SSH host and CONNECT to it
  FTP [ OPEN ]           Make an FTP connection
  HTTP OPEN              Make an HTTP connection
 
To return from a terminal connection to the C-Kermit prompt:
  Type your escape character followed by the letter C.
 
To display your escape character:
  SHOW ESCAPE
 
To display other settings:
  SHOW COMMUNICATIONS, SHOW TERMINAL, SHOW FILE, SHOW PROTOCOL, etc.
 
For links to manuals, books, tutorials, and more, visit the Kermit
documentation page at:
  https://www.openkermit.org/doc/
 
For an online C-Kermit intro and tutorial, visit:
  https://www.openkermit.org/ckermit/intro/
 
To learn about script programming and automation:
  http://www.openkermit.org/ckermit/scripting/
 
For further information about a particular command, type HELP xxx,
where xxx is the name of the command.  For documentation, news of new
releases, and information about other Kermit software, visit the
Open Kermit website:
 
  https://www.openkermit.org/
 
For information about technical support please visit this page:
 
  https://www.openkermit.org/support/

NEWS

Welcome to C-Kermit 11.
For changes to C-Kermit since version 9.0 of 2011, please visit
https://github.com/OpenKermit/ckermit/blob/main/doc/changelog.md 
Documentation:
 . https://www.openkermit.org/doc/
    Online index to C-Kermit documentation.
 . https://www.openkermit.org/ckermit/intro/
    C-Kermit tutorial.
 
If the release date shown by the VERSION command is long past, be sure to
check the Kermit website to see if there have been updates:
 
  https://www.openkermit.org/              (Open Kermit home page)
  https://github.com/openkermit/ckermit/   (C-Kermit project page)

LICENSE

Copyright (C) 1985, 2025,
  The Trustees of Columbia University in the City of New York.
Copyright (C) 2025-2026, John Goerzen.
All rights reserved.
 
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
 
 + Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
 
 + Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in
   the documentation and/or other materials provided with the
   distribution.
 
 + Neither the name of Columbia University nor the names of its
   contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.
 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
Portions Copyright (C) 1990, Massachusetts Institute of Technology.
Portions Copyright (C) 1991, 1993 Regents of the University of California.
Portions Copyright (C) 1991, 1992, 1993, 1994, 1995 by AT&T.
Portions Copyright (C) 1995, 1997, Eric Young <eay@cryptosoft.com>.
 
For further information, visit the Open Kermit website:
https://www.openkermit.org/ .

SUPPORT

Beginning with version 9.0, C-Kermit is Open Source software.  Beginning
with version 11.0, development has moved to the Open Kermit project at:
 
  http://www.openkermit.org/
 
The C-Kermit home page is here:
 
  http://www.openkermit.org/ckermit/
 
The documentation for C-Kermit is listed here:
 
  http://www.openkermit.org/doc/
 
A C-Kermit intro tutorial is here:
 
  http://www.openkermit.org/ckermit/intro/
 
The C-Kermit Frequently Asked Questions page is here:
 
  http://www.openkermit.org/faq/
 
and the Open Kermit Technical Support page is here:
 
  http://www.openkermit.org/support/
  
If you have a problem or question that is not addressed on the website,
visit that support page above.

Commands

_ASG

Synonym: _ASSIGN

C-Kermit on high latency links

Mon, 01 Jan 0001 00:00:00 +0000

C-Kermit on high latency links

Here I discuss using C-Kermit for links with very high latencies (measured in minutes, hours, or even days). This can include radio networks such as Meshtastic, satellite links, email as a carrier, etc.

C-Kermit’s default settings are inappropriate for these settings because timeouts will cause excessive retransmits within a few seconds. However, C-Kermit is quite flexible and can easily be configured for success in these situations.

C-Kermit over ssh

Mon, 01 Jan 0001 00:00:00 +0000

C-Kermit over ssh

This page demonstrates how helpful it can be to run C-Kermit as a wrapper over ssh.

Please read the Introduction and Tour, and especially the ssh section of the intro, before continuing. That sets out some background that will be helpful for this conversation.

We’ll look into two common examples: nested ssh, and tar over Kermit.

Nested ssh

Let’s look at a situation many of us face frequently: sshing to one host, then from there to another, and from there maybe sudo to another account. It can be quite difficult to make scp or rsync work across all of this, and if you even can, time-consuming to set up.

C-Kermit Platform-Specific Notes

Mon, 01 Jan 0001 00:00:00 +0000

C-Kermit Platform-Specific Notes

Linux

Official binaries for this release are built on Ubuntu 24.04 and are built with SSL support. They should be broadly compatible with recent releases of most distributions.

If you have issues with those binaries, try the static builds. Due to significant variations between distributions, Linux binaries are additionally available in a static build, which is linked against musl libc. These have no dependencies from the running system, and thus should be portable to many versions and distributions of Linux in the chosen architecture. However, since they do not use the system’s libraries (such as OpenSSL), they don’t benefit from security updates that your distribution may make to system libraries like OpenSSL. Therefore, I recommend not using SSL facilities on the static binaries. (Very few people use SSL in Kermit these days anyhow.) The static binaries are helpful for bootstrapping connectivity to a new (or old!) system, for instance.

C-Kermit Scripting

Mon, 01 Jan 0001 00:00:00 +0000

C-Kermit Scripting

C-Kermit has a robust and powerful scripting language built in.

As noted on the Kermit Documentation page, Kermit has prized compatibility for many years. Resources from the older Kermit Project are still online and are perfect to introduce you to the C-Kermit scripting language.

Here are some places to consult:

Introduction to C-Kermit

Mon, 01 Jan 0001 00:00:00 +0000

Introduction to C-Kermit

This is a modified version of the page I initially published at https://www.complete.org/kermit/ in August 2023. I have lightly revised it for use here. - John Goerzen, July 2026

C-Kermit is one of those things I’m fond of that’s really hard to describe. It is:

A file transfer protocol for running over serial lines, modems, or TCP/IP. The protocol is quite flexible, supporting everything from tiny embedded devices with 90-byte packets to large packets and streaming over ssh.
A FTP- or SFTP-like system-agnostic protocol for looking at directories of files on remote systems, renaming files, deleting them, etc. with a standard interface.
Capable of operating under extremely challenging conditions, including 7-bit connections, connections that otherwise “eat” certain characters, and very high latency connections.
A modem dialer.
A fully-functional standalone TCP server.
A system for inband communication over a single connection.
On Windows, a terminal emulator. (On Linux/Mac/BSD, it runs within a terminal emulator already, so doesn’t need to provide that functionality).
A thin wrapper around ssh providing new features.
A scripting engine, which can be used to automate terminal interaction, file transfer, and more. There are some pretty neat kermit scripts out there - everything from renaming JPEGs based on embedded metadata to budgeting.
It’s also a Telnet, SSH, FTP, and HTTP(S) client.

You can download kermit for hundreds of platforms, many of which are decades out of date. They all interoperate. It is rather impressive. In fact, a new version of Kermit for TOPS-20 was released in 2024! (TOPS-20 was active between 1976 and 1988). C-Kermit, which this page describes, began in 1985 and, through the Open Kermit project, still is active today.

IPv6 in C-Kermit

Mon, 01 Jan 0001 00:00:00 +0000

IPv6 in C-Kermit

C-Kermit introduced IPv6 support in version 11.0.

This support includes full IPv6 support for Kermit’s own sockets (raw, telnet, and SSL/TLS) as well as the FTP and HTTP clients. The FTP client adds support for EPRT and EPSV as necessary for IPv6.

Notes on usage

SET TCP ADDRESS-FAMILY lets you configure whether to use IPv4, IPv6, or both (the default).

When giving a string that contains an IP address and a port number separated by colons, an IPv6 address (which itself contains colons) must be enclosed in [ and ] brackets. This mimics behavior in other situations (such as URLs) where similar situations are encountered. When a port number is not expected, neither are brackets.

OpenKermit C-Kermit Changelog

Mon, 01 Jan 0001 00:00:00 +0000

OpenKermit C-Kermit Changelog

C-Kermit 11.0.510 (not yet released)

C-Kermit 11.0.509

August 20, 2026

Fixed a bug in statements like \fcvtdate(..., -4) where there was no space between the day and the year, producing outputs like Sat Nov 262005 instead of Sat Nov 26 2005.
Fixed an out-of-bounds month lookup in shuffledate() for month values outside 1-12, and corrected off-by-one whitespace stripping in date parsing. Added unit tests for these date-handling functions.

Permissions in C-Kermit

Mon, 01 Jan 0001 00:00:00 +0000

Permissions in C-Kermit

C-Kermit is somewhat unique in that it is both client and server software. Also, because of the circumstances in which it operates, those distinctions are sometimes harder to reason about.

Background

The Kermit protocol is a generic protocol for performing actions on a remote machine. It can transfer files, delete or rename files, create and remove directories, and so forth. Think of it as a standardized alternative to using ssh to connect to a remote and typing commands at the shell.

Using C-Kermit to connect to a DOS BBS

Mon, 01 Jan 0001 00:00:00 +0000

Using C-Kermit to connect to a DOS BBS

DOS BBSs typically use the DOS CP437 character set, while modern terminals use UTF-8. The line-drawing characters often used on a DOS BBS won’t show up properly on a terminal expecting UTF-8.

C-Kermit can translate live. It also supports the XModem, YModem, and ZModem protocols often used for file transfer by BBSs (you may need to install a package called lrzsz or rzsz to enable this.)

Using vsock to communicate between host and guest VMs

Mon, 01 Jan 0001 00:00:00 +0000

Using vsock to communicate between host and guest VMs

On Linux, say you’re running KVM to run a guest VM. You’d like to transfer files between the host machine and the VM. There are several options for that:

Sharing some filesystem from the host (requires support in the guest and careful configuration)
Using network tools (requires setting up a network on both the host and the guest and all the configuration and security that goes with that)

Working with Wildcards, Spaces in Filenames, and More

Mon, 01 Jan 0001 00:00:00 +0000

Working with Wildcards, Spaces in Filenames, and More

These topics are are all related to specifying filenames in C-Kermit. Let’s dive in.

Quoting a filename that contains a space

Kermit treats a bare space as the end of a filename. To include a space in a filename, wrap the whole name in one of two delimiters:

Braces: {a file.txt}
Quotation marks (double quotes): "a file.txt"

Both work the same way in any command that takes a filename. Braces are always available. Double quote wrapping can be turned off with SET COMMAND DOUBLEQUOTING OFF, but is on by default.