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
              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 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

       -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 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 /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 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'
              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 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'
              ''      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. 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.

       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
       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.

       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)
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