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CHAT(8)                     System Manager's Manual                    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.

       -S     Do not use syslog(3).  By default, error messages  are  sent  to
              syslog(3).   The  use  of -S will prevent both log messages from
              '-v' and error messages from being sent to syslog(3).

       -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,  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:

              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

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

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
       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 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.

       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
              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)