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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

       -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

       -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.

       -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  out-
	      put  strings  sent  to the modem.	 The default is to log through
	      the SYSLOG; the logging method may be altered with the -S and -s

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

       -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,	 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

       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 pro-
       gram, for example, 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 written 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 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  charac-
       ter 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 ter-
       minate 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 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  /var/log/ppp/con-

       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 log-
	      ging 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 anal-
       ysis 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  use-
       ful, 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:

       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.

       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.

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

       all  output resulting from modem configuration and dialing is not visi-
       ble, 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 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 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 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.

       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 pro-
       cessing 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 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  the  SYSLOG  file.  The	string
	      ??????  is  written  to  the  log	 in  its place.	 (not valid in

       \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.

       \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  character.   (some  characters are not valid in

       ^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 variable 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 "-subsend" string. This may mean that you did not  pro-
	      gram  the	 script correctly for the condition or that some unex-
	      pected event has occurred and the expected string could  not  be

       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

       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	 docu-
       mentation.  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)