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[unix-history] / usr / contrib / kermit / ckuker.doc

9. UNIX KERMIT

Program:       Frank da Cruz, Bill Catchings, Jeff Damens, Columbia University;
               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.
\f


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 7-bit 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


    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-
    appear.

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
     delimiter.
   - Option-arguments cannot be optional.
   - Arguments immediately follow options, separated by whitespace.
\f


   - 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  ASCII
        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.    If
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 (meta)
        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
        in 

          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:
\f


        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
        in 

          kermit -l /dev/ttyi5 -b 9600
\f


        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
        character.

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   (normally
        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
        below.

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
\f


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-return-linefeed
     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
\f


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.


    kermit

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
\f


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.
\f


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

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:
\f


    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.


                              THE 'SEND' COMMAND

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  (see
\f


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 "#".


                             THE 'RECEIVE' COMMAND

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'.


                              THE 'GET' COMMAND:

Syntax:  get rfn

      or: get
              rfn
              fn1

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

  C-Kermit>get
   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.
\f


  C-Kermit>get
   Remote file specification: foo
   Local name to store it under: (Type a carriage return here)
  (cancelled)
  C-Kermit>


                             THE 'SERVER' COMMAND:

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  Berkeley
C-Shell.


                  THE 'REMOTE', 'BYE', AND 'FINISH' COMMANDS:

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
\f


        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.


                        THE 'LOG' AND 'CLOSE' COMMANDS:

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  Kermit
    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.
\f


                        LOCAL FILE MANAGEMENT COMMANDS:

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.


                        THE 'SET' AND 'SHOW' COMMANDS:

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  'send'
    command.  Used in remote mode to give you time to escape back to your local
    Kermit and issue a 'receive' command.  Normally 5 seconds.
\f


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
        overhead.

    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) Kermit
        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
\f


            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, Kermit
    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, Kermit
    will revert to its default mode of operation.   If  you  specify  /dev/tty,
    Kermit  will  enter  remote  mode  (useful when logged in through the "back
    port" of a system normally used as a local-mode workstation).    When  Unix
    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  'set
    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  8th-bit
    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]
\f


    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-Kermit>".
    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.    Shorter
        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
        character.

    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  Kermit
        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-
    ets.
\f


    end-of-packet cc
        Requests the other Kermit to terminate its packets with  the  specified
        character.

    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
    speed'.


                              THE 'SHOW' COMMAND:

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:

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).
\f


                        THE 'TAKE' AND 'ECHO' COMMANDS:

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-
\f


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:

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:
\f


  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'.


                              THE 'DIAL' COMMAND:

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 DF03-AC
   - 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
\f


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 (say,
"/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 carrier-detect
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
  Connected!
  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:

  kermit
  C-Kermit>set modem-dialer ventel
  C-Kermit>set line /dev/cul0
  C-Kermit>dial 9&5551212%
  Connected!
  C-Kermit> ...

Example three:

  kermit
  C-Kermit>take my-dial-procedure
  Connected!

  file my-dial-procedure:
  set modem hayes
  set line /dev/tty99
  dial 5551212
  connect

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-
\f


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.


                             THE 'SCRIPT' COMMAND:

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
~c.

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:  
\f


  -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
  connect

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 @--@--@ id~saa001122 = 002211 @ \
      c~s12345 ystem-c~s12345-ystem myhost @ joe~ssecret @ kermit \
      > set~sparity~seven > server
  send some.stuff
  get some.otherstuff
  bye
  quit
\f


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
  end

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.


                              THE 'HELP' COMMAND:

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.


                        THE 'EXIT' AND 'QUIT' COMMANDS:

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
     ready.
   - 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.
\f


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 

  /usr/spool/uucp/LCK..ttyi6

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).
\f


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 System
III/V, the usual  interrupt  function  (often  the  DEL  key)  is  replaced  by
Control-C.)

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.  Venix
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
\f


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 Kermit.
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  Backspace),
      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  (unless
      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  'set
      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 Ker-
      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
\f


      dial-out or dedicated line for the "set line" or "-l" options.  Most
      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
      C-Kermit).

      A  simple  shell program can be used to change directionality of the
      line if your Unix has the enable(8) and  disable(8)  commands.    In
      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.  The
      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 XON/XOFF
      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-Kermit
      terminates abnormally (say, for example, by a kill command issued by
      the  operator)  the  user  may need to reset the terminal state.  If
      commands do not seem  to  be  accepted  at  the  shell  prompt,  try
      Control-J  "stty  sane"  Control-J  (use  "reset" on Berkeley Unix).
      That should take the terminal out of "raw  mode"  if  it  was  stuck
      there.

   8. Remote  host  commands  may  time-out  on  lengthy  activity:  Using
      "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.
\f


   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 (i.e.
      hung).


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 "wermit".
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
\f


  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
  d:    MS-DOS
  m:    Macintosh
  u:    Unix
  v:    VAX/VMS
  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  compiler-dependent
    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
\f


    be regarded as a subset of the Unix "lex" lexical analyzer generator.  Wart
    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 (which
    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.
\f


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,  Penril,
    Racal-Vadic, and several other modems.

ckuscr.c (Unix):
    This is the login script  module.    As  supplied,  it  handles  uucp-style
    scripts.

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.    If
      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-
\f


     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,
     etc.

   - 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.