CHAT(8)                                                                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 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.

       -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  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 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

       -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 inter-
       val 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
       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 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
              $ \c
              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 ...

       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:

       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'
              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.

       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 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'
              ''      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 ...

       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
       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 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  substitution  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.

       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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