9. UNIX KERMIT University;

9. UNIX KERMIT University;


Program: Frank da Cruz, Bill Catchings, Jeff Damens, Columbia


Herm Fischer, Encino CA; contributions by many others.

Language: C

Documentation: Frank da Cruz, Herm Fischer

Version: 4C(057)

Date: July 26, 1985

C-Kermit is a completely new implementation of Kermit, written modularly and transportably in C. The protocol state transition table is written in wart, a

(non-proprietary) lex-like preprocessor for C. System-dependent primitive func- tions are isolated into separately compiled modules so that the program should be easily portable among Unix systems and also to non-Unix systems that have C compilers. This document applies to Unix implementations of C-Kermit, and in most ways also to the VMS implementation.

Unix Kermit Capabilities At A Glance:

Local operation: Yes

Remote operation: Yes

Login scripts: Yes

Transfer text files: Yes

Transfer binary files: Yes

Wildcard send: Yes

File transfer interruption: Yes

Filename collision avoidance: Yes

Can time out: Yes

8th-bit prefixing: Yes

Repeat count prefixing: Yes

Alternate block checks: Yes

Terminal emulation: Yes

Communication settings: Yes

Transmit BREAK: Yes

Support for dialout modems: Yes

IBM mainframe communication: Yes

Transaction logging: Yes

Session logging: Yes

Debug logging: Yes

Packet logging: Yes

Act as server: Yes

Talk to server: Yes

Advanced server functions: Yes

Local file management: Yes

Command/Init files: Yes

UUCP and multiuser line locking: Yes

File attributes packets: No

Command macros: No

Raw file transmit: No

C-Kermit provides traditional Unix command line operation as well as inter- active command prompting and execution. The command line options provide ac- cess to a minimal subset of C-Kermit's capabilities; the interactive command set is far richer.

On systems with dialout modems, C-Kermit can use its command file and login script facilities to replicate the file transfer functionality of UUCP among heterogeneous operating systems, including the use of scheduled (e.g. late night) unattended operation.

9.1. The Unix File System

Consult your Unix manual for details about the file system under your version of Unix. For the purposes of Kermit, several things are worth briefly noting.

Unix files generally have lowercase names, possibly containing one or more dots or other special characters. Unix directories are tree-structured.

Directory levels are separated by slash ("/") characters. For example,

/usr/foo/bar denotes the file bar in the directory /usr/foo. Wildcard or "meta" characters allow groups of files to be specified. "*" matches any string; "?" matches any single character.

When C-Kermit is invoked with file arguments specified on the Unix command line, the Unix shell (Bourne Shell, C-Shell, etc) expands the meta characters itself, and in this case a wider variety is available. For example,

kermit -s ~/ck[uvm]*.{upd,bwr}] is expanded by the Berkeley C-Shell into a list of all the files in the user's home directory (~/) that start with the characters "ck", followed by a single character "u", "v", or "m", followed by zero or more characters, followed by a dot, followed by one of the strings "upd" or "bwr". Internally, the C-

Kermit program itself expands only the "*" and "?" meta characters.

Unix files are linear streams of 8-bit bytes. Text files consist of 7bit AS-

CII characters, with the high-order bit off (0), and lines separated by the

Unix newline character, which is linefeed (LF, ASCII 10). This distinguishes

Unix text files from those on most other ASCII systems, in which lines are separated by a carriage-return linefeed sequence (CRLF, ASCII 13 followed by

ASCII 10). Binary files are likely to contain data in the high bits of the file bytes, and have no particular line or record structure.

When transferring files, C-Kermit will convert between upper and lower case filenames and between LF and CRLF line terminators automatically, unless told to do otherwise. When binary files must be transferred, the program must be instructed not to perform LF/CRLF conversion (-i on the command line or

"set file type binary" interactively; see below).

9.2. File Transfer

If C-Kermit is in local mode, the screen (stdout) is continously updated to show the progress of the file transer. A dot is printed for every four data packets, other packets are shown by type:

I Exchange Parameter Information

R Receive Initiate

S Send Initiate

F File Header

G Generic Server Command

C Remote Host Command

N Negative Acknowledgement (NAK)

E Fatal Error

T Indicates a timeout occurred

Q Indicates a damaged, undesired, or illegal packet was received

% Indicates a packet was retransmitted

You may type certain "interrupt" commands during file transfer:

Control-F: Interrupt the current File, and go on to the next (if any).

Control-B: Interrupt the entire Batch of files, terminate the transaction.

Control-R: Resend the current packet

Control-A: Display a status report for the current transaction.

These interrupt characters differ from the ones used in other Kermit implemen- tations to avoid conflict with commonly used Unix shell interrupt characters.

With Version 7, System III, and System V implementations of Unix, interrupt commands must be preceeded by the 'connect' escape character (e.g. normally-\).

CAUTION: If Control-F or Control-B is used to cancel an incoming file,

and a file of the same name previously existed, and the "file warning"

feature is not enabled, then the previous copy of the file will dis-


EMERGENCY EXIT: When running Unix Kermit in remote mode, if you have started a protocol operation (sending or receiving a file, server command wait, etc), you will not be able to regain control of the terminal until the protocol operation has run its course (completed or timed out). In particular, you cannot stop the protocol by typing the normal Unix interrupt characters, since the terminal has been put in "raw mode". If you need to regain control quickly -- for in- stance, because the protocol is stuck -- you can type the following sequence of four characters directly to the Unix Kermit program ("connect" first if necessary):

Control-A Control-C Control-C Carriage-Return

This will cause the program to exit and restore the terminal to normal.

9.3. Command Line Operation

The C-Kermit command line syntax has been changed from that of earlier releases of Unix Kermit to conform to the Proposed Syntax Standards for Unix

System Com- mands put forth by Kathy Hemenway and Helene Armitage of AT&T Bell

Laboratories in Unix/World, Vol.1, No.3, 1984. The rules that apply are:

- Command names must be between 2 and 9 characters ("kermit" is 6).

- Command names must include lower case letters and digits only.

- An option name is a single character.

- Options are delimited by '-'.

- Options with no arguments may be grouped (bundled) behind one


- Option-arguments cannot be optional.

- Arguments immediately follow options, separated by whitespace.

- The order of options does not matter.

- '-' preceded and followed by whitespace means standard input.

A group of bundled options may end with an option that has an argument.

The following notation is used in command descriptions: fn A Unix file specification, possibly containing the "wildcard" charac-

ters `*' or `?' (`*' matches all character strings, `?' matches any

single character). fn1 A Unix file specification which may not contain `*' or `?'. rfn A remote file specification in the remote system's own syntax, which

may denote a single file or a group of files. rfn1 A remote file specification which should denote only a single file. n A decimal number between 0 and 94. c A decimal number between 0 and 127 representing the value of an


character. cc A decimal number between 0 and 31, or else exactly 127, representing

the value of an ASCII control character.

[ ] Any field in square braces is optional.

{x,y,z} Alternatives are listed in curly braces.

C-Kermit command line options may specify either actions or settings.


C-Kermit is invoked with a command line that specifies no actions, then it will issue a prompt and begin interactive dialog. Action options specify either protocol transactions or terminal connection.

-s fn Send the specified file or files. If fn contains wildcard


characters, the Unix shell expands it into a list. If fn is '-' then

kermit sends from standard input, which must come from a file:

kermit -s - < foo.bar

or a parallel process:

ls -l | kermit -s -

You cannot use this mechanism to send terminal typein. If you want to

send a file whose name is "-" you can precede it with a path name, as


kermit -s ./-

-r Receive a file or files. Wait passively for files to arrive.

-k Receive (passively) a file or files, sending them to standard output.

This option can be used in several ways:

kermit -k

Displays the incoming files on your screen; to be used only in

"local mode" (see below).

kermit -k > fn1

Sends the incoming file or files to the named file, fn1.

If more

than one file arrives, all are concatenated together into the

single file fn1.

kermit -k | command

Pipes the incoming data (single or multiple files) to the indicated

command, as in

kermit -k | sort > sorted.stuff

-a fn1 If you have specified a file transfer option, you may specify an alter-

nate name for a single file with the -a option. For example,

kermit -s foo -a bar

sends the file foo telling the receiver that its name is bar. If more

than one file arrives or is sent, only the first file is affected by

the -a option:

kermit -ra baz

stores the first incoming file under the name baz.

-x Begin server operation. May be used in either local or remote mode.

Before proceeding, a few words about remote and local operation are necessary.

C-Kermit is "local" if it is running on PC or workstation that you are using directly, or if it is running on a multiuser system and transferring files over an external communication line -- not your job's controlling terminal or con- sole. C-Kermit is remote if it is running on a multiuser system and transfer- ring files over its own controlling terminal's communication line, connected to your PC or workstation.

If you are running C-Kermit on a PC, it is in local mode by default, with the

"back port" designated for file transfer and terminal connection. If you are running C-Kermit on a multiuser (timesharing) system, it is in remote mode un- less you explicitly point it at an external line for file transfer or terminal connection. The following command sets C-Kermit's "mode":

-l dev Line -- Specify a terminal line to use for file transfer and terminal

connection, as in

kermit -l /dev/ttyi5

When an external line is being used, you might also need some additional op- tions for successful communication with the remote system:

-b n Baud -- Specify the baud rate for the line given in the -l option, as


kermit -l /dev/ttyi5 -b 9600

This option should always be included with the -l option, since the

speed of an external line is not necessarily what you expect.

-p x Parity -- e,o,m,s,n (even, odd, mark, space, or none). If parity is

other than none, then the 8th-bit prefixing mechanism will be used for

transferring 8-bit binary data, provided the opposite Kermit agrees.

The default parity is none.

-t Specifies half duplex, line turnaround with XON as the handshake


The following commands may be used only with a C-Kermit which is local -

- ei- ther by default or else because the -l option has been specified.

-g rfn Actively request a remote server to send the named file or files; rfn

is a file specification in the remote host's own syntax. If fn happens

to contain any special shell characters, like '*', these must be

quoted, as in

kermit -g x\*.\?

-f Send a 'finish' command to a remote server.

-c Establish a terminal connection over the specified or default com-

munication line, before any protocol transaction takes place.

Get back

to the local system by typing the escape character


Control-Backslash) followed by the letter 'c'.

-n Like -c, but after a protocol transaction takes place; -c and

-n may

both be used in the same command. The use of -n and -c is illustrated


On a timesharing system, the -l and -b options will also have to be included with the -r, -k, or -s options if the other Kermit is on a remote system.

Several other command-line options are provided:

-i Specifies that files should be sent or received exactly "as is" with no

conversions. This option is necessary for transmitting binary files.

It may also be used to slightly boost efficiency in Unix-to-Unix trans-

fers of text files by eliminating CRLF/newline conversion.

-w Write-Protect -- Avoid filename collisions for incoming files.

-q Quiet -- Suppress screen update during file transfer, for instance to

allow a file transfer to proceed in the background.

-d Debug -- Record debugging information in the file debug.log in the cur-

rent directory. Use this option if you believe the program is mis-

behaving, and show the resulting log to your local kermit maintainer.

-h Help -- Display a brief synopsis of the command line options.

The command line may contain no more than one protocol action option.

Files are sent with their own names, except that lowercase letters are raised

to upper, pathnames are stripped off, certain special characters like

(`~') and

(`#') are changed to `X', and if the file name begins with a period, an

`X' is inserted before it. Incoming files are stored under their own names except that uppercase letters are lowered, and, if -w was specified, a

"generation number" is appended to the name if it has the same name as an existing file which would otherwise be overwritten. If the -a option is included, then the same rules apply to its argument. The file transfer display shows any trans- formations performed upon filenames.

During transmission, files are encoded as follows:

- Control characters are converted to prefixed printables.

- Sequences of repeated characters are collapsed via repeat counts, if

the other Kermit is also capable of repeated-character compression.

- If parity is being used on the communication line, data characters

with the 8th (parity) bit on are specially prefixed, provided the

other Kermit is capable of 8th-bit prefixing; if not, 8-bit binary

files cannot be successfully transferred.

- Conversion is done between Unix newlines and carriage-returnlinefeed

sequences unless the -i option was specified.

Command Line Examples:

kermit -l /dev/ttyi5 -b 1200 -cn -r

This command connects you to the system on the other end of ttyi5 at 1200 baud, where you presumably log in and run Kermit with a 'send' command.

After you escape back, C-Kermit waits for a file (or files) to arrive. When the file transfer is completed, you are again connected to the remote system so that you can logout.

kermit -l /dev/ttyi4 -b 1800 -cntp m -r -a foo

This command is like the preceding one, except the remote system in this case uses half duplex communication with mark parity. The first file that arrives is stored under the name foo.

kermit -l /dev/ttyi6 -b 9600 -c | tek

This example uses Kermit to connect your terminal to the system at the other end of ttyi6. The C-Kermit terminal connection does not provide any particular terminal emulation, so C-Kermit's standard i/o is piped through a

(hypothetical) program called tek, which performs (say) Tektronix emulation.

kermit -l /dev/ttyi6 -b 9600 -nf

This command would be used to shut down a remote server and then connect to the remote system, in order to log out or to make further use of it. The -n option

is invoked after -f (-c would have been invoked before).

kermit -l /dev/ttyi6 -b 9600 -qg foo.\* &

This command causes C-Kermit to be invoked in the background, getting a group of files from a remote server (note the quoting of the `*' character).

No dis- play occurs on the screen, and the keyboard is not sampled for interruption commands. This allows other work to be done while file transfers proceed in the background.

kermit -l /dev/ttyi6 -b 9600 -g foo.\* > foo.log < /dev/null &

This command is like the previous one, except the file transfer display has been redirected to the file foo.log. Standard input is also redirected, to prevent C-Kermit from sampling it for interruption commands.

kermit -iwx

This command starts up C-Kermit as a server. Files are transmitted with no newline/carriage-return-linefeed conversion; the -i option is necessary for bi- nary file transfer and useful for Unix-to-Unix transfers. Incoming files that have the same names as existing files are given new, unique names.

kermit -l /dev/ttyi6 -b 9600

This command sets the communication line and speed. Since no action is specified, C-Kermit issues a prompt and enters an interactive dialog with you.

Any settings given on the command line remain in force during the dialog, un- less explicitly changed.


This command starts up Kermit interactively with all default settings.

The next example shows how Unix Kermit might be used to send an entire direc- tory tree from one Unix system to another, using the tar program as

Kermit's standard input and output. On the orginating system, in this case the remote, type (for instance):

tar cf - /usr/fdc | kermit -is -

This causes tar to send the directory /usr/fdc (and all its files and all its subdirectories and all their files...) to standard output instead of to a tape; kermit receives this as standard input and sends it as a binary file.

On the receiving system, in this case the local one, type (for instance):

kermit -il /dev/ttyi5 -b 9600 -k | tar xf -

Kermit receives the tar archive, and sends it via standard output to its own

copy of tar, which extracts from it a replica of the original directory tree.

A final example shows how a Unix compression utility might be used to speed up

Kermit file transfers:

compress file | kermit -is - (sender)

kermit -ik | uncompress (receiver)

Exit Status Codes:

Unix Kermit returns an exit status of zero, except when a fatal error is en- countered, where the exit status is set to one. With background operation

(e.g., `&' at end of invoking command line) driven by scripted interactive com- mands (redirected standard input and/or take files), any failed interactive command (such as failed dial or script attempt) causes the fatal error exit.

9.4. Interactive Operation

C-Kermit's interactive command prompt is "C-Kermit>". In response to this prompt, you may type any valid command. C-Kermit executes the command and then prompts you for another command. The process continues until you instruct the program to terminate.

Commands begin with a keyword, normally an English verb, such as

"send". You may omit trailing characters from any keyword, so long as you specify suf- ficient characters to distinguish it from any other keyword valid in that field. Certain commonly-used keywords (such as "send", "receive",

"connect") have special non-unique abbreviations ("s" for "send", "r" for

"receive", "c" for "connect").

Certain characters have special functions during typein of interactive com- mands:

? Question mark, typed at any point in a command, will produce a message

explaining what is possible or expected at that point.

Depending on

the context, the message may be a brief phrase, a menu of keywords, or

a list of files.

ESC (The Escape or Altmode key) -- Request completion of the current

keyword or filename, or insertion of a default value. The result will

be a beep if the requested operation fails.

DEL (The Delete or Rubout key) -- Delete the previous character from the

command. You may also use BS (Backspace, Control-H) for this function.

^W (Control-W) -- Erase the rightmost word from the command line.

^U (Control-U) -- Erase the entire command.

^R (Control-R) -- Redisplay the current command.

SP (Space) -- Delimits fields (keywords, filenames, numbers) within a com-

mand. HT (Horizontal Tab) may also be used for this purpose.

CR (Carriage Return) -- Enters the command for execution. LF


or FF (formfeed) may also be used for this purpose.

\ (Backslash) -- Enter any of the above characters into the command,

literally. To enter a backslash, type two backslashes in a row


A backslash at the end of a command line causes the next line to be

treated as a continuation line; this is useful for readability in com-

mand files, especially in the 'script' command.

You may type the editing characters (DEL, ^W, etc) repeatedly, to delete all the way back to the prompt. No action will be performed until the command is entered by typing carriage return, linefeed, or formfeed. If you make any mis- takes, you will receive an informative error message and a new prompt -- make liberal use of `?' and ESC to feel your way through the commands. One impor- tant command is "help" -- you should use it the first time you run C-


A command line beginning with a percent sign "%" is ignored. Such lines may be used to include illustrative commentary in Kermit command dialogs.

Interactive C-Kermit accepts commands from files as well as from the keyboard.

When you enter interactive dialog, C-Kermit looks for the file .kermrc in your home or current directory (first it looks in the home directory, then in the current one) and executes any commands it finds there. These commands must be in interactive format, not Unix command-line format. A "take" command is also provided for use at any time during an interactive session. Command files may be nested to any reasonable depth.

Here is a brief list of C-Kermit interactive commands:

! Execute a Unix shell command, or start a shell.

bye Terminate and log out a remote Kermit server.

close Close a log file.

connect Establish a terminal connection to a remote system.

cwd Change Working Directory.

dial Dial a telephone number.

directory Display a directory listing.

echo Display arguments literally.

exit Exit from the program, closing any open files.

finish Instruct a remote Kermit server to exit, but not log out.

get Get files from a remote Kermit server.

help Display a help message for a given command.

log Open a log file -- debugging, packet, session, transaction.

quit Same as 'exit'.

receive Passively wait for files to arrive.

remote Issue file management commands to a remote Kermit server.

script Execute a login script with a remote system.

send Send files.

server Begin server operation.

set Set various parameters.

show Display values of 'set' parameters.

space Display current disk space usage.

statistics Display statistics about most recent transaction.

take Execute commands from a file.

The 'set' parameters are:

block-check Level of packet error detection.

delay How long to wait before sending first packet.

duplex Specify which side echoes during 'connect'.

escape-character Prefix for "escape commands" during 'connect'.

file Set various file parameters.

flow-control Communication line full-duplex flow control.

handshake Communication line half-duplex turnaround character.

incomplete Disposition for incompletely received files.

line Communication line device name.

modem-dialer Type of modem-dialer on communication line.

parity Communication line character parity.

prompt The C-Kermit program's interactive command prompt.

receive Parameters for inbound packets.

send Parameters for outbound packets.

speed Communication line speed.

The 'remote' commands are:

cwd Change remote working directory.

delete Delete remote files.

directory Display a listing of remote file names.

help Request help from a remote server.

host Issue a command to the remote host in its own command language

space Display current disk space usage on remote system.

type Display a remote file on your screen.

who Display who's logged in, or get information about a user.

Most of these commands are described adequately in the Kermit User Guide.

Spe- cial aspects of certain Unix Kermit commands are described below.


Syntax: send fn - or - send fn1 rfn1

Send the file or files denoted by fn to the other Kermit, which should be run- ning as a server, or which should be given the 'receive' command. Each file is sent under its own name (as described above, or as specified by the 'set file names' command). If the second form of the 'send' command is used, i.e. with fn1 denoting a single Unix file, rfn1 may be specified as a name to send it un- der. The 'send' command may be abbreviated to 's', even though 's' is not a unique abbreviation for a top-level C-Kermit command.

The wildcard (meta) characters `*' and `?' are accepted in fn. If `?' is to be included, it must be prefixed by `\' to override its normal function of provid- ing help. `*' matches any string, `?' matches any single character.

Other notations for file groups, like `[a-z]og', are not available in interactive commands (though of course they are available on the command line).

When fn contains `*' or `?' characters, there is a limit to the number of files that can be matched, which varies from system to system. If you get the message

"Too many files match" then you'll have to make a more judicious selection. If fn was of the form

usr/longname/anotherlongname/* then C-Kermit's string space will fill up rapidly -- try doing a cwd


below) to the path in question and reissuing the command.

Note -- C-Kermit sends only from the current or specified directory.

It does not traverse directory trees. If the source directory contains subdirectories, they will be skipped. Conversely, C-Kermit does not create directories when receiving files. If you have a need to do this, you can pipe tar through

C-Kermit, as shown in the example on page 125, or under System III/V

Unix you can use cpio.

Another Note -- C-Kermit does not skip over "invisible" files that match the file specification; Unix systems usually treat files whose names start with a dot (like .login, .cshrc, and .kermrc) as invisible. Similarly for

"temporary" files whose names start with "#".


Syntax: receive - or - receive fn1

Passively wait for files to arrive from the other Kermit, which must be given the 'send' command -- the 'receive' command does not work in conjunction with a server (use 'get' for that). If fn1 is specified, store the first incoming file under that name. The 'receive' command may be abbreviated to 'r'.


Syntax: get rfn

or: get



Request a remote Kermit server to send the named file or files. Since a remote file specification (or list) might contain spaces, which normally delimit fields of a C-Kermit command, an alternate form of the command is provided to allow the inbound file to be given a new name: type 'get' alone on a line, and

you will be prompted separately for the remote and local file specifications, for example


Remote file specification: profile exec

Local name to store it under: profile.exec

As with 'receive', if more than one file arrives as a result of the

'get' com- mand, only the first will be stored under the alternate name given by fn1; the remaining files will be stored under their own names if possible. If a

`?' is to be included in the remote file specification, you must prefix it with

`\' to suppress its normal function of providing help.

If you have started a multiline 'get' command, you may escape from its lower- level prompts by typing a carriage return in response to the prompt, e.g.


Remote file specification: foo

Local name to store it under: (Type a carriage return here)




The 'server' command places C-Kermit in "server mode" on the currently selected communication line. All further commands must arrive as valid Kermit packets from the Kermit on the other end of the line. The Unix Kermit server can respond to the following commands:

Command Server Response

get Sends files

send Receives files

bye Attempts to log itself out

finish Exits to level from which it was invoked

remote directory Sends directory lising

remote delete Removes files

remote cwd Changes working directory

remote type Sends files to your screen

remote space Reports about its disk usage

remote who Shows who's logged in

remote host Executes a Unix shell command

remote help Lists these capabilities

Note that the Unix Kermit server cannot always respond to a BYE command. It will attempt to do so using "kill()", but this will not work on all systems or under all conditions.

If the Kermit server is directed at an external line (i.e. it is in

"local mode") then the console may be used for other work if you have 'set file dis- play off'; normally the program expects the console to be used to observe file transfers and enter status queries or interruption commands. The way to get

C-Kermit into background operation from interactive command level varies from system to system (e.g. on Berkeley Unix you would halt the program with

^Z and then use the C-Shell 'bg' command to continue it in the background).

The more

common method is to invoke the program with the desired command line arguments, including "-q", and with a terminating "&".

When the Unix Kermit server is given a 'remote host' command, it executes it using the shell invoked upon login, e.g. the Bourne shell or the




C-Kermit may itself request services from a remote Kermit server. In addition to 'send' and 'get', the following commands may also be sent from C-

Kermit to a

Kermit server:

remote cwd [directory]

If the optional remote directory specification is included, you will be

prompted on a separate line for a password, which will not echo as you

type it.

remote delete rfn delete remote file or files.

remote directory [rfn] directory listing of remote files.

remote host command command in remote host's own command language.

remote space disk usage report from remote host.

remote type [rfn] display remote file or files on the screen.

remote who [user] display information about who's logged in.

remote help display remote server's capabilities.

bye and finish:

When connected to a remote Kermit server, these commands cause the

remote server to terminate; 'finish' returns it to Kermit or system

command level (depending on the implementation or how the program was

invoked); 'bye' also requests it to log itself out.


Syntax: log {debugging, packets, session, transactions} [ fn1 ]

C-Kermit's progress may be logged in various ways. The 'log' command opens a log, the 'close' command closes it. In addition, all open logs are closed by the 'exit' and 'quit' commands. A name may be specified for a log file; if the name is omitted, the file is created with a default name as shown below. log debugging

This produces a voluminous log of the internal workings of C-Kermit, of use

to Kermit developers or maintainers in tracking down suspected bugs in the

C-Kermit program. Use of this feature dramatically slows down the


protocol. Default name: debug.log. log packets

This produces a record of all the packets that go in and out of the com-

munication port. This log is of use to Kermit maintainers who are tracking

down protocol problems in either C-Kermit or any Kermit that C-

Kermit is

connected to. Default name: packet.log. log session

This log will contain a copy of everything you see on your screen during

the 'connect' command, except for local messages or interaction with local

escape commands. Default name: session.log. log transactions

The transaction log is a record of all the files that were sent or received

while transaction logging was in effect. It includes time stamps and

statistics, filename transformations, and records of any errors that may

have occurred. The transaction log allows you to have long unattended file

transfer sessions without fear of missing some vital screen message.

Default name: transact.log.

The 'close' command explicitly closes a log, e.g. 'close debug'.

Note: Debug and Transaction logs are a compile-time option; C-Kermit may be compiled without these logs, in which case it will run faster, it will take up less space on the disk, and the commands relating to them will not be present.


Unix Kermit allows some degree of local file management from interactive com- mand level: directory [fn]

Displays a listing of the names, modes, sizes, and dates of files matching

fn (which defaults to `*'). Equivalent to `ls -l'. cwd [directory-name]

Changes Kermit's working directory to the one given, or to the default

directory if the directory name is omitted. This command affects only the

Kermit process and any processes it may subsequently create. space

Display information about disk space and/or quota in the current directory

and device.

! [command]

The command is executed by the Unix shell. If no command is specified,

then an interactive shell is started; exiting from the shell, e.g. by

typing Control-D, will return you to C-Kermit command level. C-

Kermit at-

tempts to use your preferred, customary shell. Use the `!' command to

provide file management or other functions not explicitly provided by

C-Kermit commands. The `!' command has certain peculiarities:

- At least one space must separate the '!' from the shell command.

- A 'cd' command executed in this manner will have no effect -- use

the C-Kermit 'cwd' command instead.


Since Kermit is designed to allow diverse systems to communicate, it is often necessary to issue special instructions to allow the program to adapt to peculiarities of the another system or the communication path. These instruc- tions are accomplished by the 'set' command. The 'show' command may be used to

display current settings. Here is a brief synopsis of settings available in the current release of C-Kermit: block-check {1, 2, 3}

Determines the level of per-packet error detection. "1" is a single-

character 6-bit checksum, folded to include the values of all bits from

each character. "2" is a 2-character, 12-bit checksum.

"3" is a

3-character, 16-bit cyclic redundancy check (CRC). The higher the block

check, the better the error detection and correction and the higher the

resulting overhead. Type 1 is most commonly used; it is supported by all

Kermit implementations, and it has proven adequate in most circumstances.

Types 2 or 3 would be used to advantage when transferring 8-bit binary

files over noisy lines. delay n

How many seconds to wait before sending the first packet after a


command. Used in remote mode to give you time to escape back to your local

Kermit and issue a 'receive' command. Normally 5 seconds.

duplex {full, half}

For use during 'connect'. Specifies which side is doing the echoing;

'full' means the other side, 'half' means C-Kermit must echo typein itself. escape-character cc

For use during 'connect' to get C-Kermit's attention. The escape character

acts as a prefix to an 'escape command', for instance to close the connec-

tion and return to C-Kermit or Unix command level. The normal escape

character is Control-Backslash (28). The escape character is also used in

System III/V implementations to prefix interrupt commands during file

transfers. file {display, names, type, warning}

Establish various file-related parameters:

display {on, off}

Normally 'on'; when in local mode, display progress of file transfers

on the screen (stdout), and listen to the keyboard (stdin) for inter-

ruptions. If off (-q on command line) none of this is done, and the

file transfer may proceed in the background oblivious to any other work

concurrently done at the console terminal.

names {converted, literal}

Normally converted, which mean that outbound filenames have path

specifications stripped, lowercase letters raised to upper, tildes and

extra periods changed to X's, and an X inserted in front of any name

that starts with period. Incoming files have uppercase letters

lowered. Literal means that none of these conversions are done; there-

fore, any directory path appearing in a received file specification

must exist and be write-accessible. When literal naming is being used,

the sender should not use path names in the file specification unless

the same path exists on the target system and is writable.

type {binary, text}

Normally text, which means that conversion is done between Unix newline

characters and the carriage-return/linefeed sequences required by the

canonical Kermit file transmission format, and in common use on non-

Unix systems. Binary means to transmit file contents without conver-

sion. Binary (`-i' in command line notation) is necessary for binary

files, and desirable in all Unix-to-Unix transactions to cut down on


warning {on, off}

Normally off, which means that incoming files will silently overwrite

existing files of the same name. When on (`-w' on command line)


will check if an arriving file would overwrite an existing file; if so,

it will construct a new name for the arriving file, of the form foo~n,

where foo is the name they share and n is a "generation number"; if foo

exists, then the new file will be called foo~1. If foo and foo~1 ex-

ist, the new file will be foo~2, and so on. If the new name would be

longer than the maximum length for a filename, then characters would be

deleted from the end first, for instance, thelongestname on a system

with a limit of 14 characters would become thelongestn~1.

CAUTION: If Control-F or Control-B is used to cancel an incom-

ing file, and a file of the same name previously existed, and

the "file warning" feature is not enabled, then the previous

copy of the file will disappear. flow-control {none, xon/xoff}

Normally xon/xoff for full duplex flow control. Should be set to

'none' if

the other system cannot do xon/xoff flow control, or if you have issued a

'set handshake' command. If set to xon/xoff, then handshake should be set

to none. This setting applies during both terminal connection and file

transfer. incomplete {discard, keep}

Disposition for incompletely received files. If an incoming file is inter-

rupted or an error occurs during transfer, the part that was received so

far is normally discarded. If you "set incomplete keep" then such file

fragments will be kept. handshake {xon, xoff, cr, lf, bell, esc, none}

Normally none. Otherwise, half-duplex communication line turnaround hand-

shaking is done, which means Unix Kermit will not reply to a packet until

it has received the indicated handshake character or has timed out waiting

for it; the handshake setting applies only during file transfer.

If you

set handshake to other than none, then flow should be set to none. line [device-name]

The device name for the communication line to be used for file transfer and

terminal connection, e.g. /dev/ttyi3. If you specify a device name,


will be in local mode, and you should remember to issue any other necessary

'set' commands, such as 'set speed'. If you omit the device name,


will revert to its default mode of operation. If you specify


Kermit will enter remote mode (useful when logged in through the


port" of a system normally used as a local-mode workstation). When


Kermit enters local mode, it attempts to synchronize with other programs

(like uucp) that use external communication lines so as to prevent two

programs using the same line at once; before attempting to lock the

specified line, it will close and unlock any external line that was

previously in use. The method used for locking is the "uucp lock file",

explained in more detail later. modem-dialer {direct, hayes, racalvadic, ventel, ...}

The type of modem dialer on the communication line. "Direct" indicates ei-

ther there is no dialout modem, or that if the line requires carrier detec-

tion to open, then 'set line' will hang waiting for an incoming call.

"Hayes", "Ventel", and the others indicate that 'set line' (or the -l

argument) will prepare for a subsequent 'dial' command for the given

dialer. Support for new dialers is added from time to time, so type


modem ?' for a list of those supported in your copy of Kermit.

See the

description of the 'dial' command parity {even, odd, mark, space, none}

Specify character parity for use in packets and terminal connection, nor-

mally none. If other than none, C-Kermit will seek to use the


prefixing mechanism for transferring 8-bit binary data, which can be used

successfully only if the other Kermit agrees; if not, 8-bit binary data

cannot be successfully transferred. prompt [string]

The given string will be substituted for "C-Kermit>" as this program's

prompt. If the string is omitted, the prompt will revert to "C-


If the string is enclosed in doublequotes, the quotes will be stripped and

any leading and trailing blanks will be retained. send parameter

Establish parameters to use when sending packets. These will be in effect

only for the initial packet sent, since the other Kermit may override these

parameters during the protocol parameter exchange (unless noted below).

end-of-packet cc

Specifies the control character needed by the other Kermit to recognize

the end of a packet. C-Kermit sends this character at the end of each

packet. Normally 13 (carriage return), which most Kermit implemen-

tations require. Other Kermits require no terminator at all, still

others may require a different terminator, like linefeed (10).

packet-length n

Specify the maximum packet length to send. Normally 90.


packet lengths can be useful on noisy lines, or with systems or front

ends or networks that have small buffers. The shorter the packet, the

higher the overhead, but the lower the chance of a packet being cor-

rupted by noise, and the less time to retransmit corrupted packets.

This command overrides the value requested by the other Kermit during

protocol initiation.

pad-character cc

Designate a character to send before each packet. Normally, none is

sent. Outbound padding is sometimes necessary for communicating with

slow half duplex systems that provide no other means of line turnaround

control. It can also be used to send special characters to communica-

tions equipment that needs to be put in "transparent" or "no echo"

mode, when this can be accomplished in by feeding it a certain control


padding n

How many pad characters to send, normally 0.

start-of-packet cc

The normal Kermit packet prefix is Control-A (1); this command changes

the prefix C-Kermit puts on outbound packets. The only reasons this

should ever be changed would be: Some piece of equipment somewhere be-

tween the two Kermit programs will not pass through a Control-

A; or,

some piece of of equipment similarly placed is echoing its input. In

the latter case, the recipient of such an echo can change the packet

prefix for outbound packets to be different from that of arriving pack-

ets, so that the echoed packets will be ignored. The opposite


must also be told to change the prefix for its inbound packets.

timeout n

Specifies the number of seconds you want the other Kermit to wait for a

packet before timing it out and requesting retransmission. receive parameter

Establish parameters to request the other Kermit to use when sending pack-


end-of-packet cc

Requests the other Kermit to terminate its packets with the specified


packet-length n

Specify the maximum packet length to that you want the other

Kermit to

send. Normally 90.

pad-character cc

C-Kermit normally does not need to have incoming packets preceded with

pad characters. This command allows C-Kermit to request the other Ker-

mit to use cc as a pad character. Default cc is NUL, ASCII 0.

padding n

How many pad characters to ask for, normally 0.

start-of-packet cc

Change the prefix C-Kermit looks for on inbound packets to correspond

with what the other Kermit is sending.

timeout n

Normally, each Kermit partner sets its packet timeout interval based on

what the opposite Kermit requests. This command allows you to override

the normal procedure and specify a timeout interval for Unix

Kermit to

use when waiting for packets from the other Kermit. If you specify 0,

then no timeouts will occur, and Unix Kermit will wait forever for ex-

pected packets to arrive. speed {0, 110, 150, 300, 600, 1200, 1800, 2400, 4800, 9600}

The baud rate for the external communication line. This command cannot be

used to change the speed of your own console terminal. Many Unix systems

are set up in such a way that you must give this command after a 'set line'

command before you can use the line. 'set baud' is a synomym for 'set



Syntax: show {parameters, versions}

The "show" command with the default argument of "parameters" displays the values of all the 'set' parameters described above. If you type

"show versions", then C-Kermit will display the version numbers and dates of all its internal modules. You should use the "show versions" command to ascertain the vintage of your Kermit program before reporting problems to Kermit maintainers.


The statistics command displays information about the most recent

Kermit protocol transaction, including file and communication line i/o, timing and ef- ficiency, as well as what encoding options were in effect (such as

8th-bit prefixing, repeat-count compression).


Syntax: take fn1

echo [text to be echoed]

The 'take' command instructs C-Kermit to execute commands from the named file.

The file may contain any interactive C-Kermit commands, including 'take'; com- mand files may be nested to any reasonable depth. The 'echo' command may be used within command files to issue greetings, announce progress, ring the ter- minal bell, etc.

The 'echo' command should not be confused with the Unix 'echo' command, which can be used to show how meta characters would be expanded. The Kermit echo command simply displays its text argument (almost) literally at the terminal; the argument may contain octal escapes of the form "\ooo", where o is an octal digit (0-7), and there may be 1, 2, or 3 such digits, whose value specify an

ASCII character, such as "\007" (or "\07" or just "\7") for beep,

"\012" for newline, etc. Of course, each backslash must be must be entered twice in order for it to be passed along to the echo command by the Kermit command parser.

Take-command files are in exactly the same syntax as interactive commands.

Note that this implies that if you want to include special characters like question mark or backslash that you would have to quote with backslash when typing interactive commands, you must quote these characters the same way in command files. Long lines may be continued by ending them with a single back- slash.

Command files may be used in lieu of command macros, which have not been imple- mented in this version of C-Kermit. For instance, if you commonly connect to a system called 'B' that is connected to ttyh7 at 4800 baud, you could create a file called b containing the commands

% C-Kermit command file to connect to System B thru /dev/ttyh7

set line /dev/ttyh7

set speed 4800

% Beep and give message

echo \\007Connecting to System B...

connect and then simply type 'take b' (or 't b' since no other commands begin with the letter 't') whenever you wish to connect to system B. Note the comment lines and the beep inserted into the 'echo' command.

For connecting to IBM mainframes, a number of 'set' commands are required; these, too, are conveniently collected into a 'take' file like this one:

% Sample C-Kermit command file to set up current line

% for IBM mainframe communication


set parity mark

set handshake xon

set flow-control none

set duplex half

Note that no single command is available to wipe out all of these settings and return C-Kermit to its default startup state; to do that, you can either res-

tart the program, or else make a command file that executes the necessary

'set' commands:

% Sample C-Kermit command file to restore normal settings


set parity none

set handshake none

set flow-control xon/xoff

set duplex full

An implicit 'take' command is executed upon your .kermrc file upon C-

Kermit's initial entry into interactive dialog. The .kermrc file should contain

'set' or other commands you want to be in effect at all times. For instance, you might want override the default action when incoming files have the same names as existing files -- in that case, put the command

set file warning on in your .kermrc file. On some non-Unix systems that run C-Kermit, this file might have a different name, such as kermit.ini.

NOTE: The initialization file is currently not processed if Kermit is

invoked with an action command from the command line. The same effect

can be achieved, however, by defining an alias or shell procedure that

starts up Kermit with the desired command line options.

Commands executed from take files are not echoed at the terminal. If you want to see the commands as well as their output, you could feed the command file to

C-Kermit via redirected stdin, as in

'kermit < cmdfile'

Errors encountered during execution of take files (such as failure to complete dial or script operations) cause termination of the current take file, popping to the level that invoked it (take file, interactive level, or the shell).

When kermit is executed in the background, errors during execution of a take file are fatal.


The connect command links your terminal to another computer as if it were a lo- cal terminal to that computer, through the device specified in the most recent

'set line' command, or through the default device if your system is a

PC or workstation. All characters you type at your keyboard are sent out the com- munication line, all characters arriving at the communication port are dis- played on your screen. Current settings of speed, parity, duplex, and flow- control are honored. If you have issued a 'log session' command, everything you see on your screen will also be recorded to your session log.

This provides a way to "capture" files from systems that don't have Kermit programs available.

To get back to your own system, you must type the escape character, which is

Control-Backslash (^\) unless you have changed it with the 'set escape' com- mand, followed by a single-character command, such as 'c' for

"close connection". Single-character commands include:

c Close the connection

b Send a BREAK signal

0 (zero) send a null

s Give a status report about the connection

h Hangup the phone

^\ Send Control-Backslash itself (whatever you have defined the escape

character to be, typed twice in a row sends one copy of it).

Uppercase and control equivalents for these letters are also accepted. A space typed after the escape character is ignored. Any other character will produce a beep.

The connect command simply displays incoming characters on the screen.

It is assumed any screen control sequences sent by the host will be handled by the firmware in your terminal or PC. If terminal emulation is desired, then the connect command can invoked from the Unix command line (-c or -n), piped through a terminal emulation filter, e.g.

kermit -l /dev/acu -b 1200 -c | tek

'c' is an acceptable non-unique abbreviation for 'connect'.


Syntax: dial telephone-number-string

This command controls dialout modems; you should have already issued a "set line" and "set speed" command to identify the terminal device, and a

"set modem" command to identify the type of modem to be used for dialing.

In the

"dial" command, you supply the phone number and the Kermit program feeds it to the modem in the appropriate format and then interprets dialer return codes and modem signals to inform you whether the call was completed. The telephone- number-string may contain imbedded modem-dialer commands, such as comma for

Hayes pause, or `&' for Ventel dialtone wait and `%' for Ventel pause

(consult your modem manual for details).

At the time of this writing, support is included for the following modems:

- Cermetek Info-Mate 212A


- DEC DF100 Series

- DEC DF200 Series

- General DataComm 212A/ED

- Hayes Smartmodem 1200 and compatibles

- Penril

- Racal Vadic

- US Robotics 212A

- Ventel

Support for new modems is added to the program from time to time; you can check the current list by typing "set modem ?".

The device used for dialing out is the one selected in the most recent

"set line" command (or on a workstation, the default line if no "set line" command was given). The "dial" command calls locks the path (see the section on line

locking below) and establishes a call on an exclusive basis. If it is desired to dial a call and then return to the shell (such as to do kermit activities depending on standard in/out redirection), it is necessary to place the dialed call under one device name (say, "/dev/cua0") and then escape to the shell within Kermit on a linked device which is separate from the dialed line


"/dev/cul0"). This is the same technique used by uucp (to allow locks to be placed separately for dialing and conversing).

Because modem dialers have strict requirements to override the carrierdetect signal most Unix implementations expect, the sequence for dialing is more rigid than most other C-Kermit procedures.

Example one:

kermit -l /dev/cul0 -b 1200

C-Kermit>set modem-dialer hayes hint: abbreviate set m h

C-Kermit>dial 9,5551212


C-Kermit>connect hint: abbreviate c

logon, request remote server, etc.

C-Kermit> ...

C-Kermit>quit hint: abbreviate q this disconnects modem, and unlocks line.

Example two:


C-Kermit>set modem-dialer ventel

C-Kermit>set line /dev/cul0

C-Kermit>dial 9&5551212%


C-Kermit> ...

Example three:


C-Kermit>take my-dial-procedure


file my-dial-procedure:

set modem hayes

set line /dev/tty99

dial 5551212


For Hayes dialers, two important switch settings are #1 and #6. #1 should be up so that the DTR is only asserted when the line is 'open'. #6 should be up so carrier-detect functions properly. Switches #2 (English versus digit result codes) and #4 (Hayes echoes modem commands) may be in either position.

For any dialers in general, this Kermit program requires that the modem provide the "carrier detect" signal when a call is in progress, and remove that signal when the call completes or the line drops. If a switch setting is available to force carrier detect, it should not be in that setting. Secondly, this

Kermit program requires that the modem track the computer's "data terminal ready" sig-

nal (DTR). If a switch setting is available to simulate DTR asserted within the modem, then it should not be in that setting. Otherwise the modem will be unable to hang up at the end of a call or when interrupts are received by Ker- mit.

If you want to interrupt a dial command in progress (for instance, because you just realize that you gave it the wrong number), type a Control-C to get back to command level.


Syntax: script expect send [expect send] . . .

"expect" has the syntax: expect[-send-expect[-send-expect[...]]]

This command facilitates logging into a remote system and/or invoking programs or other facilities after login on a remote system.

This login script facility operates in a manner similar to that commonly used by the Unix uucp System's "L.sys" file entries. A login script is a sequence of the form:

expect send [expect send] . . . where expect is a prompt or message to be issued by the remote site, and send is the string (names, numbers, etc) to return. The send may also be the keyword EOT, to send Control-D, or BREAK, to send a break signal.

Letters in send may be prefixed by `~' to send special characters. These are:

~b backspace

~s space

~q `?'(trapped by Kermit's command interpreter)

~n linefeed

~r carriage return

~t tab

~' single quote

~~ tilde

~" double quote

~x XON (Control-Q)

~c don't append a carriage return

~o[o[o]] an octal character

~d delay approx 1/3 second during send

~w[d[d]] wait specified interval during expect, then time out

As with some uucp systems, sent strings are followed by ~r unless they have a


Only the last 7 characters in each expect are matched. A null expect, e.g. ~0 or two adjacent dashes, causes a short delay before proceeding to the next send sequence. A null expect always succeeds.

As with uucp, if the expect string does not arrive, the script attempt fails.

If you expect that a sequence might not arrive, as with uucp, conditional se- quences may be expressed in the form:

-send-expect[-send-expect[...]] where dashed sequences are followed as long as previous expects fail.

Timeouts for expects can be specified using ~w; ~w with no arguments waits 15 seconds.

Expect/send transactions can be easily be debugged by logging transactions.

This records all exchanges, both expected and actual.

Note that `\' characters in login scripts, as in any other C-Kermit interactive commands, must be doubled up. A line may be ended with a single `\' for con- tinuation.

Example one:

Using a modem, dial a UNIX host site. Expect "login" (...gin), and if it doesn't come, simply send a null string with a ~r. (Some Unixes require either an EOT or a BREAK instead of the null sequence, depending on the particular site's "logger" program.) After providing user id and password, respond

"x" to a question-mark prompt, expect the Bourne shell "$" prompt (and send return if it doesn't arrive). Then cd to directory kermit, and run the program called

"wermit", entering the interactive connect state after wermit is loaded.

set modem-dialer ventel

set line /dev/tty77

set baud 1200

dial 9&5551212

script gin:--gin:--gin: smith ssword: mysecret ~q x $--$ \

cd~skermit $ wermit


Example two:

Using a modem, dial the Telenet network. This network expects three returns with slight delays between them. These are sent following null expects.

The single return is here sent as a null string, with a return appended by default.

Four returns are sent to be safe before looking for the prompt.

Then the

Telenet id and password are entered. Then telenet is instructed to connect to a host site (c 12345). The host has a data switch, and to "which system" it responds "myhost". This is followed by a TOPS-20 logon, and a request to load

Kermit, set even parity, and enter the server mode. Files are then exchanged.

The commands are in a take file; note the continuation of the 'script' command onto several lines using the `\' terminator.

set modem-dialer hayes

set line /dev/cul0

set baud 1200

dial 9,5551212

set parity even

script ~0 ~0 ~0 ~0 ~0 ~0 ~0 ~0 @[email protected]@ id~saa001122 = 002211 @ \

c~s12345 ystem-c~s12345-ystem myhost @ joe~ssecret @ kermit \

> set~sparity~seven > server

send some.stuff

get some.otherstuff



Since these commands may be executed totally in the background, they can also be scheduled. A typical shell script, which might be scheduled by cron, would be as follows (csh used for this example):


#keep trying to dial and log onto remote host and exchange files

#wait 10 minutes before retrying if dial or script fail.


cd someplace

while ( 1 )

kermit < /tonight.cmd >> nightly.log &

if ( ! $status ) break

sleep 600


File tonight.cmd might have two takes in it, for example, one to take a file with the set modem, set line, set baud, dial, and script, and a second take of a file with send/get commands for the remote server. The last lines of tonight.cmd should be a bye and a quit.


Syntax: help

or: help keyword

or: help {set, remote} keyword

Brief help messages or menus are always available at interactive command level by typing a question mark at any point. A slightly more verbose form of help is available through the 'help' command. The 'help' command with no arguments prints a brief summary of how to enter commands and how to get further help.

'help' may be followed by one of the top-level C-Kermit command keywords, such as 'send', to request information about a command. Commands such as

'set' and

'remote' have a further level of help. Thus you may type 'help', 'help set', or 'help set parity'; each will provide a successively more detailed level of help.


These two commands are identical. Both of them do the following:

- Attempt to insure that the terminal is returned to normal.

- Relinquish access to any communication line assigned via 'set line'.

- Relinquish any uucp and multiuser locks on the communications line.

- Hang up the modem, if the communications line supports data terminal


- Close any open log files.

After exit from C-Kermit, your default directory will be the same as when you started the program. The 'exit' command is issued implicitly whenever C-

Kermit halts normally, e.g. after a command line invocation, or after certain kinds of interruptions.

9.5. UUCP Lock Files

Unix has no standard way of obtaining exclusive access to an external com- munication line. When you issue the 'set line' command to Unix Kermit,

Unix would normally grant you access to the line even if some other process is making use of it. The method adopted by most Unix systems to handle this situation is the "UUCP lock file". UUCP, the Unix-to-Unix Copy program, creates a file in its directory (usually /usr/spool/uucp, on some systems

/etc/locks) with a name like LCK..name, where name is the device name, for in- stance tty07.

Unix Kermit uses UUCP lock files in order to avoid conflicts with UUCP, tip, or other programs that follow this convention. Whenever you attempt to access an external line using the 'set line' command or `-l' on the command line,

Kermit looks in the UUCP directory for a lock file corresponding to that device. For instance, if you 'set line /dev/ttyi6' then Kermit looks for the file


If it finds this file, it gives you an error message and a directory listing of the file so that you can see who is using it, e.g.

-r--r--r-- 1 fdc 4 May 7 13:02 /usr/spool/uucp/LCK..ttyi6

In this case, you would look up user fdc to find out how soon the line will be- come free.

This convention requires that the uucp directory be publicly readable and writable. If it is not, the program will issue an appropriate warning message, but will allow you to proceed at your own risk (and the risk of anyone else who might also be using the same line).

If no lock file is found, Unix Kermit will attempt create one, thus preventing anyone who subsequently tries to run Kermit, UUCP, tip, or similar programs on

the same line from gaining access until you release the line. If Kermit could not create the lock file (for instance because the uucp directory is write- protected), then you will receive a warning message but will be allowed to proceed at your -- and everyone else's -- risk. When Kermit terminates nor- mally, your lock file is removed.

Even when the lock directory is writable and readable, the locking mechanism depends upon all users using the same name for the same device. If a device has more than one path associated with it, then a lock can be circumvented by using an alias.

When a lock-creating program abruptly terminates, e.g. because it crashes or is killed via shell command, the lock file remains in the uucp directory, spuriously indicating that the line is in use. If the lock file is owned by yourself, you may remove it. Otherwise, you'll have to get the owner or the system manager to remove it, or else wait for a system task to do so; uucp sup- ports a function (uuclean) which removes these files after a predetermined age

-- uucp sites tend to run this function periodically via crontab.

Locking is not needed, or used, if communications occur over the user's login terminal line (normally /dev/tty).

It may be seen that line locking is fraught with peril. It is included in Unix

Kermit only because other Unix communication programs rely on it. While it is naturally desirable to assure exclusive access to a line, it is also un- desirable to refuse access to a vacant line only because of a spurious lock file, or because the uucp directory is not appropriately protected.

9.6. C-Kermit under Berkeley or System III/V Unix:

C-Kermit may be interrupted at command level or during file transfer by typing

Control-C. The program will perform its normal exit function, restoring the terminal and releasing any lock. If a protocol transaction was in progress, an error packet will be sent to the opposite Kermit so that it can terminate cleanly.

C-Kermit may be invoked in the background ("&" on shell commmand line).

If a background process is "killed", the user will have to manually remove any lock file and may need to restore the modem. This is because the kill signal

(kill(x,9)) cannot be trapped by Kermit.

During execution of a system command ('directory', 'cwd', or `!'), C-

Kermit can often be returned to command level by typing a single Control-C. (With


III/V, the usual interrupt function (often the DEL key) is replaced by


Under Berkeley Unix only: C-Kermit may also be interrupted by ^Z to put the process in the background. In this case the terminal is not restored.

You will have to type Control-J followed by "reset" followed by another

Control-J to get your terminal back to normal.

Control-C, Control-Z, and Control-\ lose their normal functions during terminal connection and also during file transfer when the controlling tty line is being used for packet i/o.

If you are running C-Kermit in "quiet mode" in the foreground, then interrupt- ing the program with a console interrupt like Control-C will not restore the terminal to normal conversational operation. This is because the system call to enable console interrupt traps will cause the program to block if it's run- ning in the background, and the primary reason for quiet mode is to allow the program to run in the background without blocking, so that you can do other work in the foreground.

If C-Kermit is run in the background ("&" on shell commmand line), then the in- terrupt signal (Control-C) (and System III/V quit signal) are ignored.

This prevents an interrupt signal intended for a foreground job (say a compilation) from being trapped by a background Kermit session.

9.7. C-Kermit on the DEC Pro-3xx with Pro/Venix Version 1

The DEC Professional 300 series are PDP-11/23 based personal computers.


Version 1 is a Unix v7 derivative. It should not be confused with Venix

Ver- sion 2, which is based on ATT System V; these comments apply to Venix

Version 1 only. C-Kermit runs in local mode on the Pro-3xx when invoked from the con- sole; the default device is /dev/com1.dout. When connected to a remote system

(using C-Kermit's 'connect' command), Pro/Venix itself (not Kermit) provides

VT52 terminal emulation. Terminal operation at high speeds (like 9600 baud) requires xon/xoff flow control, which unfortunately interferes with applica- tions such as the EMACS that use Control-Q and Control-S as commands.

When logging in to a Pro-3xx (or any workstation) through the "back port", it may be necessary to give the command "set line /dev/tty" in order to get

C-Kermit to function correctly in remote mode (on a system in which it normally expects to be operating in local mode).

9.8. C-Kermit under VAX/VMS

Version 4C of C-Kermit can be built using VAX-11 C to run under VMS.

Most of the descriptions in this manual hold true, but it should be noted that as of this writing the VMS support is not thoroughly tested, and no explicit support exists for the various types of VMS files and their attributes.

The C-Kermit init file for VMS is called KERMIT.INI.

9.9. C-Kermit on the Macintosh

The "protocol kernel" of C-Kermit is also used by Columbia's Macintosh


The user and system interface is entirely different, and is covered in a separate document.

9.10. C-Kermit Restrictions and Known Bugs

1. Editing characters: The program's interactive command interrupt,

delete, and kill characters are Control-C, Delete (or


and Control-U, respectively. There is currently no way to change

them to suit your taste or match those used by your shell, in case

those are different.

2. High baud rates: There's no way to specify baud rates higher than

9600 baud. Most Unix systems don't supply symbols for them


you use EXTA, EXTB), and even when they do, the program has no way

of knowing whether a specific port's serial i/o controller supports

those rates.

3. Modem controls: If a connection is made over a communication line

(rather than on the controlling terminal line), and that line has

modem controls, (e.g. data terminal ready and carrier detection

implementation), returning to the shell level will disconnect the

conversation. In that case, one should use interactive mode com-

mands, and avoid use of piped shell-level operation (also see


modem-dialer' and 'dial' commands.)

4. Login Scripts: The present login scripts implementation follows the

Unix conventions of uucp's "L.sys" file, rather than the normal


mit "INPUT/OUTPUT" style, so there's no way to arbitrarily mingle

script output with Kermit commands (e.g. changing parity or duplex

in the middle of a script).

5. Dial-out vs dial-in communications lines: C-Kermit requires a

dial-out or dedicated line for the "set line" or "-l" options.


systems have some lines dedicated to dial-in, which they enable

"loggers" on, and some lines available for dial-out. Where a line

must be shared between dial-in and dial-out, several options are

available (though they are, strictly speaking, outside the pervue of


A simple shell program can be used to change directionality of the

line if your Unix has the enable(8) and disable(8) commands.


that case, the shell program could "grep" a "who" to see if anybody

is logged onto the desired line; if not, it could "disable" the

line. The shell program will need to be set-uID'ed to root.


shell program can be called from kermit prior to a dial command,

e.g., "! mydisable.shellprog". Prior to the final "quit" from

C-Kermit, another shell program could be executed to "enable" the

line again. This program also needs to be set-uID'ed to root.

If your Unix lacks the enable(8) and disable(8) commands, another

common technique works if your system supports the /etc/ttys file.

A shell program could call up an awk program to find the line in the

file and set the enable byte to 0 (to directly disable the line).

Likewise, it can be reenabled by a counterpart at the end. It may

be necessary to pause for 60 seconds after modifying that file be-

fore the logger sees it and actually disables the line.

6. Using C-Kermit on Local Area Networks: C-Kermit can successfully

operate at speeds up to 9600 baud over LANs, provided the network

buffers are big enough to accommodate Kermit packets (which are al-

most always less than 100 characters long).

When computers are connected to LAN's through asynchronous terminal

interfaces, then the connection should be configured to do


flow control between the network interface and the computer, rather

than passing these signals through transparently. This can help

prevent Kermit from overrunning the LAN's buffers if they are small

(or if the LAN is congested), and will can also prevent the LAN from

overrunning a slow Kermit's buffers.

If the network hardware cannot accept 100 characters at a time, and

flow control cannot be done between the network and the computer,

then Kermit's "set send/receive packet-length" command can be used

to shorten the packets.

7. Resetting terminal after abnormal termination or kill: When C-


terminates abnormally (say, for example, by a kill command issued by

the operator) the user may need to reset the terminal state.


commands do not seem to be accepted at the shell prompt, try

Control-J "stty sane" Control-J (use "reset" on Berkeley


That should take the terminal out of "raw mode" if it was stuck


8. Remote host commands may time-out on lengthy activity:


"remote host" to instruct the C-Kermit server to invoke Unix func-

tions (like "make") that might take a long time to produce output

can cause timeout conditions.

9. XOFF deadlocks: When connecting back to C-Kermit after a trans-

action, or after finishing the server, it may be necessary to type a

Control-Q to clear up an XOFF deadlock. There's not much the

program can do about this...

10. PC/IX Login Scripts -- Unfound Bug: Though login scripts appear to

work properly on most processors, in the case of the PC/XT with

PC/IX, it appears that longer scripts need to be broken up into

shorter scripts (invoked sequentially from the take file). This is

because the portion of the script handler which checks if an opera-

tion timed out seems to leave the processor in a strange state



9.11. How to Build C-Kermit for a Unix System

The C-Kermit files, as distributed from Columbia, all begin with the prefix

"ck". You should make a directory for these files and then cd to it. A makefile is provided to build C-Kermit for various Unix systems

(there are separate makefiles for VMS and the Macintosh). As distributed, the makefile has the name "ckuker.mak". You should rename it to "makefile" and then type

"make xxx", where xxx is the symbol for your system, for instance "make bsd" to make C-Kermit for 4.x BSD Unix. The result will be a program called


You should test this to make sure it works; if it does, then you can rename it to "kermit" and install it for general use. See the makefile for a list of the systems supported and the corresponding "make" arguments.

9.12. Adapting C-Kermit to Other Systems

C-Kermit is designed for portability. The level of portability is indicated in parentheses after the module name: "C" means any system that has a C compiler

that conforms to the description in "The C Programming Language" by

Kernighan &

Ritchie (Prentice-Hall, 1978). "Cf" is like "C", but also requires

"standard" features like printf and fprintf, argument passing via argv/argc, and so on, as described in Kernighan & Ritchie. "Unix" means the module should be useful un- der any Unix implementation; it requires features such as fork() and pipes.

Anything else means that the module is particular to the indicated system.

C-Kermit file names are of the form: ck<system><what>.<type> where the part before the dot is no more than 6 characters long, the part after the dot no more than 3 characters long, and:

<type> is the file type:

c: C language source

h: Header file for C language source

w: Wart preprocessor source, converted by Wart (or Lex) to a C program

nr: Nroff/Troff text formatter source

mss: Scribe text formatter source

doc: Documentation

hlp: Help text

bld: Instructions for building the program

bwr: A "beware" file - list of known bugs

upd: Program update log

mak: Makefile

<system> is a single character to tell what system the file applies to:

a: Descriptive material, documentation

c: All systems with C compilers


m: Macintosh

u: Unix


w: Wart

<what> is mnemonic (up to 3 characters) for what's in the file:

aaa: A "read-me" file, like this one

cmd: Command parsing

con: Connect command

deb: Debug/Transaction Log formats, Typedefs

dia: Modem/Dialer control

fio: System-depdendent File I/O

fns: Protocol support functions

fn2: More protocol support functions

ker: General C-Kermit definitions, information, documentation

mai: Main program

pro: Protocol

scr: Script command

tio: System-dependent terminal i/o & control and interrupt handing

usr: User interface

us2: More user interface

us3: Still more user interface

Examples: ckufio.c File i/o for Unix ckmtio.c Terminal i/o for Macintosh ckuker.mss Scribe source for for Kermit User Guide chapter ckuker.nr Nroff source file for Unix C-Kermit man page

The following material discusses each of the C-Kermit modules briefly. ckcmai.c, ckcker.h, ckcdeb.h (Cf):

This is the main program. It contains declarations for global variables

and a small amount of code to initialize some variables and invoke the com-

mand parser. In its distributed form, it assumes that command line ar-

guments are passed to it via argc and argv. Since this portion of code is

only several lines long, it should be easy to replace for systems that have

different styles of user interaction. The header files define symbols and

macros used by the various modules of C-Kermit. ckcdeb.h is the only

header file that is included by all the C-Kermit modules, so it contains

not only the debug format definitions, but also any compilerdependent

typedefs. ckwart.c (Cf), ckcpro.w (C):

The ckcpro module embodies the Kermit protocol state table and the code to

accomplish state switching. It is written in "wart", a language which may

be regarded as a subset of the Unix "lex" lexical analyzer generator.


implements enough of lex to allow the ckprot module to function.

Lex it-

self was not used because it is proprietary. The protocol module ckcpro.w

is read by wart, and a system-independent C program is produced.

The syn-

tax of a Wart program is illustrated by ckcpro.w, and is described in

ckwart.doc. ckcfns.c (C):

The module contains all the Kermit protocol support functions -- packet

formation, encoding, decoding, block check calculation, filename and data

conversion, protocol parameter negotiation, and high-level interaction with

the communication line and file system. To accommodate small systems, this

module has been split into two -- ckcfns.c and ckcfn2.c. ckutio.c:

This module contains the system-dependent primitives for communication line

i/o, timers, and interrupts for the various versions of Unix.

Certain im-

portant variables are defined in this module, which determine whether

C-Kermit is by default remote or local, what the default communication

device is, and so forth. The tio module maintains its own private database

of file descriptors and modes for the console terminal and the file trans-

fer communication line so that other modules (like ckcfns or the terminal

connect module) need not be concerned with them. The variations among Unix

implementations with respect to terminal control and timers are accom-

modated via conditional compilation. ckufio.c:

This module contains system-dependent primitives for file i/o, wildcard

(meta character) expansion, file existence and access checking, and system

command execution for the various versions of Unix. It maintains an inter-

nal database of i/o "channels" (file pointers in this case) for the files

C-Kermit cares about -- the input file (the file which is being sent), the

output file (the file being received), the various logs, the screen, and so

forth. This module varies little among Unix implementations except for the

wildcard expansion code; the directory structure of 4.2bsd Unix is dif-

ferent from that of other Unix systems. Again, variation among

Unix sys-

tems is selected using conditional compilation. ckuusr.h, ckuusr.c, ckuus2.c, ckuus3.c (Unix):

This is the "user interface" for C-Kermit. It includes the command parser,

the screen output functions, and console input functions. The command par-

ser comes in two pieces -- the traditional Unix command line decoder


is quite small and compact), and the interactive keyword parser

(which is

rather large). This module is fully replacable; its interface to the other

modules is very simple, and is explained at the beginning of the source

file. The ckuusr module also includes code to execute any commands

directly which don't require the Kermit protocol -- local file management,

etc. The module is rated "Unix" because it makes occasional use of the

system() function.

Note that while ckuusr is logically one module, it has been split up into

three C source files, plus a header file for the symbols they share in com-

mon. This is to accommodate small systems that cannot handle big modules.

ckuusr.c has the command line and top-level interactive command parser;

ckuus2.c has the help command and strings; ckuus3 has the set and remote

commands along with the logging, screen, and "interrupt" functions.

ckucmd.c, ckucmd.h (Cf):

This is an interactive command parsing package developed for C-

Kermit. It

is written portably enough to be usable on any system that has a C compiler

that supports functions like printf. The file name parsing functions

depend upon primitives defined in the fio module; if these primitives can-

not be supplied for a certain system, then the filename parsing functions

can be deleted, and the package will still be useful for parsing keywords,

numbers, arbitrary text strings, and so forth. The style of interaction is

the same as that found on the DECSYSTEM-20. ckucon.c (Unix):

This is the connect module. As supplied, it should operate in any

Unix en-

vironment, or any C-based environment that provides the fork() function.

The module requires access to global variables that specify line speed,

parity, duplex, flow control, etc, and invokes functions from the tio

module to accomplish the desired settings and input/output, and functions

from the fio module to perform session logging. No terminal emulation is

performed, but since standard i/o is used for the console, this may be

piped through a terminal emulation filter. The ckucon function may be en-

tirely replaced, so long as the global settings are honored by its replace-

ment. PC implementations of C-Kermit may require the ck?con module to do

screen control, escape sequence interpretation, etc, and may also wish to

write special code to get the best possible performance. ckudia.c (Unix):

This is the dialer module. As supplied, it handles Hayes, Ventel,


Racal-Vadic, and several other modems. ckuscr.c (Unix):

This is the login script module. As supplied, it handles uucp-style


Moving C-Kermit to a new system entails:

1. Creating a new ck?tio module in C, assembler, or whatever language

is most appropriate for system programming on the new system.


the system is Unix-like, then support may be added within the

ckutio.c module itself using conditional compilation.

2. Creating a new ck?fio module, as above.

3. If the system is not Unix-like, then a new ckuusr module may be re-

quired, as well as a different invocation of it from ckcmai.

4. If the distributed connect module doesn't work or performs poorly,

then it may be replaced. For instance, interrupt-driven i/o may be

required, especially if the system doesn't have forks.

Those who favor a different style of user/program interaction from that provided in ckuusr.c may replace the entire module, for instance with one that provides a mouse/window/icon environment, a menu/function-key environment, etc.

A few guidelines should be followed to maintain portability:

- Keep variable and function names to 6 characters or less. Don't use

identifiers that are distinguished from one another only by al-

phabetic case.

- Keep modules small. For instance, on a PDP-11 it is necessary to

keep the code segment of each module below 8K in order to allow the

segment mapping to occur which is necessary to run programs larger

than 64K on a non-I-and-D-space machine.

- Keep strings short; many compilers have restrictive maximum lengths;

128 is the smallest maximum string constant length we've encountered

so far.

- Keep (f,s)printf formats short. If these exceed some compiler de-

pendent maximum (say, 128) memory will be overwritten and the program

will probably core dump.

- Do not introduce system dependencies into ckcpro.w or ckcfn*.c.

- If a variable is a character, declare as CHAR, not int, to prevent

the various sign extension and byte swapping foulups that occur when

characters are placed in integer variables.

- Remember that different systems may use different length words for

different things. Don't assume an integer can be used as a pointer,


- Don't declare static functions; these can wreak havoc with systems

that do segment mapping.

- In conditional compilations expressions, use #ifdef and #ifndef and

not #if, which is not supported by some compilers. Also, don't use

any operators in these expressions; many compilers will fail to un-

derstand expressions like #ifdef FOO | BAR.

- Don't define multiline macros.

In general, remember that this program will have to be compilable by old com-

pilers and runnable on small systems.

Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF