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Linux 2.6 - man page for chat (linux section 8)

CHAT(8) 										  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 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.
	      You can also use the TIMEOUT string in order to specify the timeout.

       -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 substitution 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
	      stderr.

       -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 arbitrary 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.

CHAT SCRIPT
       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-
       ple:

	      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
       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

SENDING DATA FROM A FILE
       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.

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 writ-
       ten 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  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.

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  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
       /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
	      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 ...

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 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.

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 compilation 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  key-
       word  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
	      \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.

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 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'
	      ''      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. You
       can also specify "TIMEOUT 0".

       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 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.

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 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.

ESCAPE SEQUENCES
       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
	      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 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
	      expect.)

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

       \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
	      expect.)

       \\     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
       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 substitution fails, because the requested environment vari-
       able is not set, nothing is replaced for the variable.

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.

       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.

SEE ALSO
       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)

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 1.22			   22 May 1999					  CHAT(8)


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