GKERMIT(1C)                                                        GKERMIT(1C)



NAME
       gkermit - G-Kermit (GNU Kermit) 1.00 file transfer software.

SYNOPSIS
       gkermit [ options ] -s file(s)    Send files
       gkermit [ options ] -g file(s)    Get files
       gkermit [ options ] -r            Receive files


DESCRIPTION
       G-Kermit is a UNIX program for transferring files using the Kermit proto-
       col.  G-Kermit is a product of Kermit Project at Columbia University.  It
       is  free software under the GNU Public License.  See the COPYING file for
       details.


   INVOKING G-KERMIT
       The G-Kermit binary is called "gkermit".  It should be  stored  someplace
       in  your  UNIX  PATH; normally it is available as /usr/local/bin/gkermit.
       To run G-Kermit, just type "gkermit"  followed  by  command-line  options
       that tell it what to do.  If no options are given, it prints a usage mes-
       sage listing the available options.

       If an option takes an argument, the argument is required;  if  an  option
       does not take an argument, no argument may be given (exception: -d).  The
       action options are -r, -s, and -g.  Only one action option may be  given.
       If no action options are given, G-Kermit does nothing (except possibly to
       print its usage message or create a debug.log file).  Here are some exam-
       ples ("$ " is the shell prompt):

         $ gkermit -s hello.c   <-- Send the hello.c file
         $ gkermit -s hello.*   <-- Send all hello.* files
         $ gkermit -r           <-- Wait to receive files
         $ gkermit -g hello.c   <-- Get hello.c file
         $ gkermit -g hello.\*  <-- Get all hello.* files

       Options  that  do not take arguments can be "bundled" with other options.
       An option that takes an argument must always be followed by a  space  and
       then its argument(s).  Examples:

         $ gkermit -is hello.o  <-- Send hello.o in binary mode
         $ gkermit -dr          <-- Receive with debugging


   COMMAND-LINE OPTIONS
         -r      RECEIVE.  Wait for incoming files.
         -s fn   SEND.  Send file(s) specified by fn.
         -g fn   GET.  Get specified file(s) from server.
         -a fn   AS-NAME.  Alternative name for file.
         -i      IMAGE.  Binary-mode transfer (default).
         -T      TEXT. Text-mode transfer.
         -P      PATH (filename) conversion disabled.
         -w      WRITEOVER when filenames collide.
         -K      KEEP incompletely received files.
         -p x    PARITY. x = e,o,m,s,n; default = n(one).
         -e n    PACKET LENGTH.  n = 40-9000; default=4000.
         -b n    TIMEOUT.  Per-packet timeout, seconds.
         -x      XON/XOFF.  Set Xon/Xoff in the tty driver.
         --x     Unset Xon/Xoff in the tty driver.
         -S      STREAMING disabled.
         -X      EXTERNAL.  G-Kermit is an external protocol.
         -q      QUIET.  Suppress messages.
         -d      DEBUG.  Write debugging info to ./debug.log.
         -d fn   DEBUG.  Write debugging info to given file.
         -h      HELP.  Display brief usage message.

       You  may  supply  options  to G-Kermit on the command line or through the
       GKERMIT environment variable, which can contain any  valid  gkermit  com-
       mand-line  options.   These  are processed before the actual command-line
       options and so can be overridden by them.  Example for bash or ksh, which
       you  can put in your profile if you want to always keep incomplete files,
       suppress streaming, suppress messages, and use Space parity:

         export GKERMIT="-K -S -q -p s"


   MECHANICS OF FILE TRANSFER
       To transfer files with G-Kermit you must be connected through a  terminal
       emulator  to  the  UNIX system where G-Kermit is running, meaning you are
       online to UNIX and have access to the shell prompt (or to a menu that has
       an  option  to invoke G-Kermit).  The connection can be serial (direct or
       dialed) or network (Telnet, Rlogin, X.25, etc).

       When you tell G-Kermit to SEND a file (or files), e.g. with:

         $ gkermit -Ts oofa.txt

       it pauses for a second and then sends its  first  packet.   What  happens
       next depends on the capabilities of your terminal emulator:

           If  your  emulator  supports  Kermit  "autodownloads"  then  it
            receives the file automatically and puts you back in the termi-
            nal screen when done.

           Otherwise,  you'll  need to take whatever action is required by
            your emulator to get its attention: a mouse action, a keystroke
            like  Alt-x, or a character sequence like Ctrl-\ or Ctrl-] fol-
            lowed by the letter "c" (this is called  "escaping  back")  and
            then  tell  it  to receive the file.  When the transfer is com-
            plete, you must instruct your emulator to go back to its termi-
            nal screen.

       During file transfer, most terminal emulators put up some kind of running
       display of the file transfer progress.

       When you tell G-Kermit to RECEIVE (with "gkermit -r"), this requires  you
       to  escape  back  to  your  terminal emulator and instruct it to send the
       desired file(s).

       If your terminal emulator supports Kermit autodownloads AND Kermit server
       mode,  then  you  can use GET ("gkermit -g files...") rather than RECEIVE
       ("gkermit -r"), and the rest happens automatically, as when  G-Kermit  is
       sending.

   INTERRUPTING FILE TRANSFER
       G-Kermit supports file and group interruption.  The method for interrupt-
       ing a transfer depends on your terminal emulator.  For example, while the
       file-transfer  display is active, you might type the letter 'x' to cancel
       the current file and go on to the next one (if any), and the  letter  'z'
       to  cancel  the group.  Or there might be buttons you can click with your
       mouse.

       When G-Kermit is in packet mode and your terminal emulator is in its ter-
       minal  screen,  you can also type three (3) Ctrl-C characters in a row to
       make G-Kermit exit and restore the normal terminal modes.


   TEXT AND BINARY TRANSFER MODE
       When sending files in binary mode, G-Kermit sends every byte  exactly  as
       it is stored on the disk.  This mode is appropriate for program binaries,
       graphics files, tar archives, compressed files, etc,  and  is  G-Kermit's
       default  file transfer mode when sending.  When receiving files in binary
       mode, G-Kermit simply copies each byte to disk.  (Obviously the bytes are
       encoded for transmission, but the encoding and decoding procedures give a
       replica of the original file after transfer.)

       When sending files in text mode, G-Kermit converts the record  format  to
       the common one that is defined for the Kermit protocol, namely lines ter-
       minated by carriage return and linefeed (CRLF); the receiver converts the
       CRLFs  to  whatever  line-end  or record-format convention is used on its
       platform.  When receiving files in text mode, G-Kermit simply strips car-
       riage  returns, leaving only a linefeed at the end of each line, which is
       the UNIX convention.

       When receiving files, the sender's transfer mode (text or binary) predom-
       inates  if the sender gives this information to G-Kermit in a Kermit File
       Attribute packet, which of course depends on whether your terminal emula-
       tor's  Kermit  protocol has this feature.  Otherwise, if you gave a -i or
       -T option on the gkermit command line, the corresponding  mode  is  used;
       otherwise the default mode (binary) is used.

       Furthermore, when either sending or receiving, G-Kermit and your terminal
       emulator's Kermit can inform each other of their OS type (UNIX in  G-Ker-
       mit's  case).  If your emulator supports this capability, which is called
       "automatic peer recognition", and it tells G-Kermit that its platform  is
       also  UNIX,  G-Kermit and the emulator's Kermit automatically switch into
       binary mode, since no record-format conversion is necessary in this case.
       Automatic  peer  recognition is disabled automatically if you include the
       -i (image) or -T (text) option.

       When sending, G-Kermit sends all files in the same mode, text or  binary.
       There  is no automatic per-file mode switching.  When receiving, however,
       per-file switching occurs automatically based on the  incoming  Attribute
       packets, if any (explained below), that accompany each file.


   PATHNAMES
       When  SENDING  a  file,  G-Kermit  obtains the filenames from the command
       line.  It depends on the shell to expand  metacharacters  (wildcards  and
       tilde).

       G-Kermit uses the full pathname given to find and open the file, but then
       strips the pathname before sending the name to the receiver.   For  exam-
       ple:

         $ gkermit -s /etc/hosts

       results  in  the  receiver  getting a file called "HOSTS" or "hosts" (the
       directory part, "/etc/", is stripped).

       However, if a pathname is included in the -a option, the  directory  part
       is not stripped:

         $ gkermit -s /etc/hosts -a /tmp/hosts

       This  example  sends  the /etc/hosts file but tells the receiver that its
       name is "/tmp/hosts".  What the receiver does with the  pathname  is,  of
       course,  up to the receiver, which might have various options for dealing
       with incoming pathnames.

       When RECEIVING a file, G-Kermit does NOT  strip  the  pathname.   If  the
       incoming  filename  includes  a path, G-Kermit tries to store the file in
       the specified place.  If the path does not  exist,  the  transfer  fails.
       The incoming pathname can, of course, be overridden with the -a option.


   FILENAME CONVERSION
       When  sending  a  file,  G-Kermit normally converts outbound filenames to
       common form: uppercase, no more than one period, and no funny characters.
       So, for example, gkermit.tar.gz would be sent as GKERMIT_TAR.GZ.

       When receiving a file, if the name is all uppercase, G-Kermit converts it
       to all lowercase.  If the name contains any lowercase  letters,  G-Kermit
       leaves the name alone.

       If  the  automatic  peer recognition feature is available in the terminal
       emulator, and G-Kermit recognizes the emulator's platform as UNIX, G-Ker-
       mit  automatically  disables  filename  conversion  and sends and accepts
       filenames literally.

       You can force literal filenames by including the -P option on the command
       line.


   FILENAME COLLISIONS
       When G-Kermit receives a file whose name is the same as that of an exist-
       ing file, G-Kermit "backs up" the existing file by adding a unique suffix
       to  its  name.   The suffix is ".~n~", where n is a number.  This kind of
       backup suffix is compatible with GNU  EMACS  and  various  other  popular
       applications.

       To  defeat  the backup feature and have incoming files overwrite existing
       files of the same name, include the -w (writeover) option on the  command
       line.


RETURN VALUES
       G-Kermit resturns an exit status code of 0 if all actions succeeded and 1
       if any actions failed.


IMPLEMENTATION NOTES
       G-Kermit is designed to be small, portable, and stable, and  is  intended
       for  use  only on the "far end" of a connection; it does not make connec-
       tions itself, although it can be used as an external  protocol  by  other
       programs  that do make connections.  To keep it small and stable, it does
       not include sliding windows, a command or scripting language  or  charac-
       ter-set  translation.   To  keep it portable and stable, it avoids use of
       system services that are not standardized across all UNIX  varieties  and
       therefore,  in  particular,  does  not  support file timestamps, internal
       wildcard expansion, and other features that are not  implemented  consis-
       tently (or at all) across all UNIXes.


ENVIRONMENT
       A  GKERMIT environment variable may be defined (for example in your shell
       profile) to include G-Kermit command-line options; these are processed by
       G-Kermit  before  any options that are specified on the command line, and
       therefore are overriden by command-line options.


DIAGNOSTICS
       If an error occurs during file transfer G-Kermit sends an error packet to
       your  terminal emulator to cancel the transfer; an appropriate error mes-
       sage should be displayed on your screen.


ERRORS
       File transfers can fail for a number of reasons:

           Lack of read access to a source file.
           Lack of write access to a target directory.
           Lack of adequate flow control.
           Use of streaming on an unreliable connection.
           Excessive unprefixing of control characters.
           Sending bare 8-bit data on a 7-bit connection.
           Packets too long for receiver's buffers.
           Timeout interval too short for connection.

       and many others; these are covered in the references.


REFERENCES
       The Kermit protocol is specified in "Kermit, A File Transfer Protocol" by
       Frank  da  Cruz, Digital Press (1987).  A correctness proof of the Kermit
       protocol appears in "Specification and  Validation  Methods",  edited  by
       Egon  Boerger, Oxford University Press (1995).  "Using C-Kermit" by Frank
       da Cruz and Christine M. Gianone, Digital Press (1997, or later  edition)
       explains many of the terms and techniques referenced here in case you are
       not familiar with them, and also includes tutorials  on  data  communica-
       tions,  extensive  troubleshooting  and  performance  tips, etc.  Various
       other books on Kermit are available from Digital Press.  Online resources
       include:

         Web:   http://www.columbia.edu/kermit/
         FTP:   ftp://kermit.columbia.edu/kermit/g/
         News:  comp.protocols.kermit.misc
         Email: kermit-support@columbia.edu

       Also  see  the  README file distributed with G-Kermit for further detail.
       It can also be found at ftp://kermit.columbia.edu/kermit/g/README.


BUGS
       The speed of a file transfer depends not only on the  speed  of  the  two
       computers involved and the characteristics of the connection, but also on
       the capabilities and configuration of the two Kermit programs.  Kermit is
       a  fast and reliable protocol, but not all implementations of it are nec-
       essarily fast or reliable.

       Nonstreaming transfers on a TCP/IP connection might be inordinately  slow
       if one or both of the TCP/IP stacks uses the Nagle or Delayed ACK tricks.
       Streaming is used automatically if the other Kermit supports it.

       When receiving files in text mode, G-Kermit strips all carriage  returns,
       even if they aren't followed by linefeed.

       A  backups  files  are not guaranteed to have the highest number in their
       backup suffix.


AUTHOR
       Frank da Cruz, the Kermit Project, Columbia University,  New  York  City,
       December 1999.



UNIX G-Kermit                     25 Dec 1999                      GKERMIT(1C)

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