Home Man
Today's Posts

Linux & Unix Commands - Search Man Pages

RedHat 9 (Linux i386) - man page for chat (redhat section 8)

CHAT(8) 			     System Manager's Manual				  CHAT(8)

       chat - Automated conversational script with a modem

       chat [ options ] script

       The chat program defines a conversational exchange between the computer and the modem. Its
       primary purpose is to establish the connection between the Point-to-Point Protocol  Daemon
       (pppd) and the remote's pppd process.

       -f <chat file>
	      Read  the chat script from the chat file. The use of this option is mutually exclu-
	      sive with the chat script parameters. The user must have read access to  the  file.
	      Multiple lines are permitted in the file. Space or horizontal tab characters should
	      be used to separate the strings.

       -t <timeout>
	      Set the timeout for the expected string to  be  received.  If  the  string  is  not
	      received	within	the  time  limit  then the reply string is not sent. An alternate
	      reply may be sent or the script will fail if there is no alternate reply string.	A
	      failed script will cause the chat program to terminate with a non-zero error code.

       -r <report file>
	      Set  the	file for output of the report strings. If you use the keyword REPORT, the
	      resulting strings are written to this file. If this option  is  not  used  and  you
	      still use REPORT keywords, the stderr file is used for the report strings.

       -e     Start  with the echo option turned on. Echoing may also be turned on or off at spe-
	      cific points in the chat script by using the ECHO keyword. When echoing is enabled,
	      all output from the modem is echoed to stderr.

       -E     Enables  environment  variable  substituion  within chat scripts using the standard
	      $xxx syntax.

       -v     Request that the chat script be executed in a verbose mode. The chat  program  will
	      then  log  the execution state of the chat script as well as all text received from
	      the modem and the output strings sent to the modem.  The default is to log  through
	      the SYSLOG; the logging method may be altered with the -S and -s flags.

       -V     Request that the chat script be executed in a stderr verbose mode. The chat program
	      will then log all text received from the modem and the output strings sent  to  the
	      modem to the stderr device. This device is usually the local console at the station
	      running the chat or pppd program.

       -s     Use stderr.  All log messages from '-v' and all error  messages  will  be  sent  to

       -S     Do not use the SYSLOG.  By default, error messages are sent to the SYSLOG.  The use
	      of -S will prevent both log messages from '-v' and error messages from  being  sent
	      to the SYSLOG.

       -T <phone number>
	      Pass  in	an  arbitary string, usually a phone number, that will be substituted for
	      the \T substitution metacharacter in a send string.

       -U <phone number 2>
	      Pass in a second string, usually a phone number, that will be substituted  for  the
	      \U  substitution	metacharacter  in  a send string.  This is useful when dialing an
	      ISDN terminal adapter that requires two numbers.

       script If the script is not specified in a file with the -f  option  then  the  script  is
	      included as parameters to the chat program.

       The chat script defines the communications.

       A script consists of one or more "expect-send" pairs of strings, separated by spaces, with
       an optional "subexpect-subsend" string pair, separated by a dash as in the following exam-

	      ogin:-BREAK-ogin: ppp ssword: hello2u2

       This line indicates that the chat program should expect the string "ogin:". If it fails to
       receive a login prompt within the time interval allotted, it is to send a  break  sequence
       to  the	remote	and then expect the string "ogin:". If the first "ogin:" is received then
       the break sequence is not generated.

       Once it received the login prompt the chat program will	send  the  string  ppp	and  then
       expect  the  prompt  "ssword:". When it receives the prompt for the password, it will send
       the password hello2u2.

       A carriage return is normally sent following the reply string. It is not expected  in  the
       "expect" string unless it is specifically requested by using the \r character sequence.

       The expect sequence should contain only what is needed to identify the string. Since it is
       normally stored on a disk file, it should not contain variable information. It  is  gener-
       ally  not  acceptable  to  look for time strings, network identification strings, or other
       variable pieces of data as an expect string.

       To help correct for characters which may be corrupted during the  initial  sequence,  look
       for the string "ogin:" rather than "login:". It is possible that the leading "l" character
       may be received in error and you may never find the string even though it was sent by  the
       system.	For  this  reason,  scripts  look  for "ogin:" rather than "login:" and "ssword:"
       rather than "password:".

       A very simple script might look like this:

	      ogin: ppp ssword: hello2u2

       In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.

       In actual practice, simple scripts are rare. At the vary least, you  should  include  sub-
       expect  sequences  should  the  original string not be received. For example, consider the
       following script:

	      ogin:--ogin: ppp ssword: hello2u2

       This would be a better script than the simple one used earlier. This would  look  for  the
       same login: prompt, however, if one was not received, a single return sequence is sent and
       then it will look for login: again. Should line noise obscure the first login prompt  then
       sending the empty line will usually generate a login prompt again.

       Comments  can  be embedded in the chat script. A comment is a line which starts with the #
       (hash) character in column 1. Such comment lines are just ignored by the chat program.  If
       a  '#'  character  is  to  be  expected as the first character of the expect sequence, you
       should quote the expect string.	If you want to wait for a prompt that  starts  with  a	#
       (hash) character, you would have to write something like this:

	      # Now wait for the prompt and send logout string
	      '# ' logout

       If  the	string	to send starts with an at sign (@), the rest of the string is taken to be
       the name of a file to read to get the string to send.  If the last character of	the  data
       read  is  a  newline,  it is removed.  The file can be a named pipe (or fifo) instead of a
       regular file.  This provides a way for chat to communicate with another program, for exam-
       ple, a program to prompt the user and receive a password typed in.

       Many modems will report the status of the call as a string. These strings may be CONNECTED
       or NO CARRIER or BUSY. It is often desirable to terminate the script should the modem fail
       to  connect  to	the  remote. The difficulty is that a script would not know exactly which
       modem string it may receive. On one attempt, it may receive BUSY while the  next  time  it
       may receive NO CARRIER.

       These "abort" strings may be specified in the script using the ABORT sequence. It is writ-
       ten in the script as in the following example:


       This sequence will expect nothing; and then send the string ATZ. The expected response  to
       this  is the string OK. When it receives OK, the string ATDT5551212 to dial the telephone.
       The expected string is CONNECT. If the string CONNECT is received  the  remainder  of  the
       script  is  executed.  However,	should	the modem find a busy telephone, it will send the
       string BUSY. This will cause the string to match the abort character sequence. The  script
       will  then fail because it found a match to the abort string. If it received the string NO
       CARRIER, it will abort for the same reason. Either string may be received.  Either  string
       will terminate the chat script.

       This sequence allows for clearing previously set ABORT strings.	ABORT strings are kept in
       an array of a pre-determined size (at compilation time); CLR_ABORT will reclaim the  space
       for cleared entries so that new strings can use that space.

       The  SAY directive allows the script to send strings to the user at the terminal via stan-
       dard error.  If chat is being run by pppd, and pppd is running as a daemon (detached  from
       its  controlling  terminal),  standard  error  will  normally  be  redirected  to the file

       SAY strings must be enclosed in single or double quotes. If carriage return and line  feed
       are needed in the string to be output, you must explicitely add them to your string.

       The  SAY  strings  could be used to give progress messages in sections of the script where
       you want to have 'ECHO OFF' but still let the user know what is happening.  An example is:

	      ECHO OFF
	      SAY "Dialling your ISP...\n"
	      '' ATDT5551212
	      TIMEOUT 120
	      SAY "Waiting up to 2 minutes for connection ... "
	      CONNECT ''
	      SAY "Connected, now logging in ...0
	      ogin: account
	      ssword: pass
	      $ SAY "Logged in OK ...0 etc ...

       This sequence will only present the SAY strings to the user and all  the  details  of  the
       script will remain hidden. For example, if the above script works, the user will see:

	      Dialling your ISP...
	      Waiting up to 2 minutes for connection ... Connected, now logging in ...
	      Logged in OK ...

       A  report  string  is similar to the ABORT string. The difference is that the strings, and
       all characters to the next control character such as a carriage return, are written to the
       report file.

       The  report  strings  may  be used to isolate the transmission rate of the modem's connect
       string and return the value to the chat user. The analysis  of  the  report  string  logic
       occurs  in  conjunction	with  the  other string processing such as looking for the expect
       string. The use of the same string for a report and abort sequence is  probably	not  very
       useful, however, it is possible.

       The report strings to no change the completion code of the program.

       These  "report"	strings  may  be specified in the script using the REPORT sequence. It is
       written in the script as in the following example:

	      REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account

       This sequence will expect nothing; and then send the string ATDT5551212 to dial the  tele-
       phone.  The expected string is CONNECT. If the string CONNECT is received the remainder of
       the script is executed. In addition the program will write to the expect-file  the  string
       "CONNECT" plus any characters which follow it such as the connection rate.

       This  sequence allows for clearing previously set REPORT strings.  REPORT strings are kept
       in an array of a pre-determined size (at compilation time); CLR_REPORT  will  reclaim  the
       space for cleared entries so that new strings can use that space.

       The  echo  options  controls  whether  the output from the modem is echoed to stderr. This
       option may be set with the -e option, but it can also be controlled by the  ECHO  keyword.
       The  "expect-send"  pair ECHO ON enables echoing, and ECHO OFF disables it. With this key-
       word you can select which parts of the conversation should be visible. For instance,  with
       the following script:

	      ABORT   'BUSY'
	      OK\r\n  ATD1234567
	      \r\n    \c
	      ECHO    ON
	      CONNECT \c
	      ogin:   account

       all  output  resulting  from  modem configuration and dialing is not visible, but starting
       with the CONNECT (or BUSY) message, everything will be echoed.

       The HANGUP options control whether a modem hangup should be considered as an error or not.
       This  option  is  useful  in scripts for dialling systems which will hang up and call your
       system back.  The HANGUP options can be ON or OFF.
       When HANGUP is set OFF and the modem hangs up (e.g., after the first stage of  logging  in
       to a callback system), chat will continue running the script (e.g., waiting for the incom-
       ing call and second stage login prompt). As soon as the incoming call  is  connected,  you
       should  use  the HANGUP ON directive to reinstall normal hang up signal behavior.  Here is
       an (simple) example script:

	      ABORT   'BUSY'
	      OK\r\n  ATD1234567
	      \r\n    \c
	      CONNECT \c
	      'Callback login:' call_back_ID
	      ABORT "Bad Login"
	      'Callback Password:' Call_back_password
	      TIMEOUT 120
	      CONNECT \c
	      HANGUP ON
	      ogin:--BREAK--ogin: real_account
	      etc ...

       The initial timeout value is 45 seconds. This may be changed using the -t parameter.

       To change the timeout value for the next expect string, the following example may be used:

	      ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2

       This will change the timeout to 10 seconds when it expects the login: prompt. The  timeout
       is then changed to 5 seconds when it looks for the password prompt.

       The timeout, once changed, remains in effect until it is changed again.

       The special reply string of EOT indicates that the chat program should send an EOT charac-
       ter to the remote. This is normally the End-of-file character sequence. A return character
       is  not	sent  following  the  EOT.  The EOT sequence may be embedded into the send string
       using the sequence ^D.

       The special reply string of BREAK will cause a break condition to be sent. The break is	a
       special	signal on the transmitter. The normal processing on the receiver is to change the
       transmission rate.  It may be used to cycle through the available  transmission	rates  on
       the  remote until you are able to receive a valid login prompt.	The break sequence may be
       embedded into the send string using the \K sequence.

       The expect and reply strings may contain escape sequences. All of the sequences are  legal
       in  the	reply  string.	Many  are  legal in the expect.  Those which are not valid in the
       expect sequence are so indicated.

       ''     Expects or sends a null string. If you send a null string then it will  still  send
	      the  return  character.  This  sequence may either be a pair of apostrophe or quote

       \b     represents a backspace character.

       \c     Suppresses the newline at the end of the reply string. This is the only  method  to
	      send  a  string  without	a trailing return character. It must be at the end of the
	      send string. For example, the sequence hello\c will simply send the  characters  h,
	      e, l, l, o.  (not valid in expect.)

       \d     Delay  for  one  second. The program uses sleep(1) which will delay to a maximum of
	      one second.  (not valid in expect.)

       \K     Insert a BREAK (not valid in expect.)

       \n     Send a newline or linefeed character.

       \N     Send a null character. The same sequence may be represented by \0.  (not	valid  in

       \p     Pause  for  a fraction of a second. The delay is 1/10th of a second.  (not valid in

       \q     Suppress writing the string to the SYSLOG file. The string ?????? is written to the
	      log in its place.  (not valid in expect.)

       \r     Send or expect a carriage return.

       \s     Represents  a space character in the string. This may be used when it is not desir-
	      able to quote the strings which contains spaces. The sequence 'HI TIM' and  HI\sTIM
	      are the same.

       \t     Send or expect a tab character.

       \T     Send the phone number string as specified with the -T option (not valid in expect.)

       \U     Send  the  phone	number	2  string  as  specified with the -U option (not valid in

       \\     Send or expect a backslash character.

       \ddd   Collapse the octal digits (ddd) into a single ASCII character and send that charac-
	      ter.  (some characters are not valid in expect.)

       ^C     Substitute  the sequence with the control character represented by C.  For example,
	      the character DC1 (17) is shown as ^Q.  (some characters are not valid in expect.)

       Environment variables are available within chat scripts, if  the -E option  was	specified
       in  the command line. The metacharacter $ is used to introduce the name of the environment
       variable to substitute. If the substition fails, because the requested  environment  vari-
       able is not set, nothing is replaced for the variable.

       The chat program will terminate with the following completion codes.

       0      The  normal termination of the program. This indicates that the script was executed
	      without error to the normal conclusion.

       1      One or more of the parameters are invalid or an expect string was too large for the
	      internal buffers. This indicates that the program as not properly executed.

       2      An error occurred during the execution of the program. This may be due to a read or
	      write operation failing for some reason or chat receiving a signal such as SIGINT.

       3      A timeout event occurred when there was an expect string without	having	a  "-sub-
	      send"  string.  This may mean that you did not program the script correctly for the
	      condition or that some unexpected event has occurred and the expected string  could
	      not be found.

       4      The first string marked as an ABORT condition occurred.

       5      The second string marked as an ABORT condition occurred.

       6      The third string marked as an ABORT condition occurred.

       7      The fourth string marked as an ABORT condition occurred.

       ...    The other termination codes are also strings marked as an ABORT condition.

       Using the termination code, it is possible to determine which event terminated the script.
       It is possible to decide if the string "BUSY" was received from the modem  as  opposed  to
       "NO DIAL TONE". While the first event may be retried, the second will probably have little
       chance of succeeding during a retry.

       Additional information about chat scripts may be found with UUCP documentation.	The  chat
       script was taken from the ideas proposed by the scripts used by the uucico program.

       uucico(1), uucp(1)

       The  chat  program  is  in public domain. This is not the GNU public license. If it breaks
       then you get to keep both pieces.

Chat Version 1.22			   22 May 1999					  CHAT(8)

All times are GMT -4. The time now is 09:02 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
Show Password