FreeBSD Man Pages

chat(8)

NAME

       chat - Automated conversational script with a modem

SYNOPSIS

       chat [ options ] script

DESCRIPTION

       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.

OPTIONS

       -f <chat file>
	      Read the chat script from the chat file.	The use of this option
	      is mutually exclusive 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 specific points in the chat script by using
	      the ECHO keyword.  When echoing is enabled, all output from  the
	      modem is echoed to stderr.

       -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 out-
	      put strings sent to the modem.  The default is  to  log  through
	      syslog(3);  the logging method may be altered with the -S and -s
	      flags.  Logging is done to the local2 facility at level info for
	      verbose tracing and level err for some errors.

       -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 stderr.
	      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.

CHAT SCRIPT

       The chat script defines the communications.

       A script consists of one or more "expect-send" pairs of strings,  sepa-
       rated by spaces, with an optional "subexpect-subsend" string pair, sep-
       arated by a dash as in the following example:

	      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 con-
       tain variable information.  It is generally 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  ini-
       tial  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:

COMMENTS

       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

ABORT STRINGS

       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 written in the script as in the following example:

	      ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT

       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 CON-
       NECT.  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.

CLR_ABORT STRINGS

       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.

SAY STRINGS

       The  SAY directive allows the script to send strings to the user at the
       terminal via standard 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  /etc/ppp/connect-errors.

       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
       explicitly 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:

	      ABORT BUSY
	      ssword: pass
	      $ SAY "Logged in OK ...\n" 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 log-
	      ging in ...
	      Logged in OK ...

REPORT STRINGS

       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 telephone.  The expected string is CONNECT.	If the	string
       CONNECT	is received the remainder of the script is executed.  In addi-
       tion the program will write to the  expect-file	the  string  "CONNECT"
       plus any characters which follow it such as the connection rate.

CLR_REPORT STRINGS

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

ECHO

       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 keyword you can
       select  which  parts  of  the  conversation  should  be	visible.   For
       instance, with the following script:

	      ABORT   'BUSY'
	      ABORT   'NO CARRIER'
	      ''      ATZ
	      OK\r\n  ATD1234567

HANGUP

       The  HANGUP options control whether a modem hangup should be considered
       as an error or not.  This option is useful in scripts for dialling sys-
       tems  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 incoming 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 a (simple) example script:

	      ABORT   'BUSY'
	      ''      ATZ
	      OK\r\n  ATD1234567
	      \r\n    \c
	      CONNECT \c
	      'Callback login:' call_back_ID
	      HANGUP OFF
	      ABORT "Bad Login"
	      'Callback Password:' Call_back_password
	      TIMEOUT 120
	      CONNECT \c
	      HANGUP ON
	      ABORT "NO CARRIER"
	      ogin:--BREAK--ogin: real_account
	      etc ...

TIMEOUT

       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.

SENDING EOT

       The  special reply string of EOT indicates that the chat program should
       send an EOT character 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.

GENERATING BREAK

       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
       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 characters.

       \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 char-
	      acter.  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 expect.)

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

       \q     Suppress writing the string to syslogd(8).  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  desirable to quote the strings which contains
	      spaces.  The sequence 'HI TIM' and HI\sTIM are the same.

       \t     Send or expect a tab character.

       \\     Send or expect a backslash character.

       \ddd   Collapse the octal digits (ddd) into a  single  ASCII  character
	      and  send  that  character.   (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.)

TERMINATION CODES

       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.
	      pected 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.

SEE ALSO

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

       uucico(1), uucp(1), syslog(3), syslogd(8).

COPYRIGHT

       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 1.17		  27 Sep 1997			       CHAT(8)

SPONSORED LINKS