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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 Proto-
       col Daemon (pppd) and the remote's pppd process.

       -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

       -v     Request  that the chat script be executed in a ver-
              bose mode. The chat program will then log the  exe-
              cution 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

Chat Version 1.17          27 Sep 1997                          1

CHAT(8)                                                   CHAT(8)

              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 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.

       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  fol-
       lowing 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

Chat Version 1.17          27 Sep 1997                          2

CHAT(8)                                                   CHAT(8)

       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
       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 dur-
       ing 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,  how-
       ever, 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  pro-
       gram.  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

       Many  modems  will  report  the  status  of  the call as a
       string. These strings may be CONNECTED or  NO  CARRIER  or

Chat Version 1.17          27 Sep 1997                          3

CHAT(8)                                                   CHAT(8)

       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

       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.

       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  nor-
       mally 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  explicitely  add  them to your

       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

              ABORT BUSY
              ECHO OFF
              SAY "Dialling your ISP...\n"
              '' ATDT5551212

Chat Version 1.17          27 Sep 1997                          4

CHAT(8)                                                   CHAT(8)

              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  ...  Con-
              nected, now logging in ...
              Logged in OK ...

       A  report  string is similar to the ABORT string. The dif-
       ference 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

       These  "report"  strings  may  be  specified in the script
       using the REPORT sequence. It is written in the script  as
       in the following example:

              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 addition the pro-
       gram will write to the expect-file  the  string  "CONNECT"
       plus any characters which follow it such as the connection

       This sequence allows for clearing  previously  set  REPORT
       strings.   REPORT  strings  are kept in an array of a pre-

Chat Version 1.17          27 Sep 1997                          5

CHAT(8)                                                   CHAT(8)

       determined size (at  compilation  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  key-
       word.  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'
              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.

       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
       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
              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 ...

Chat Version 1.17          27 Sep 1997                          6

CHAT(8)                                                   CHAT(8)

       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  sec-
       onds 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

       The  special reply string of BREAK will cause a break con-
       dition 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  charac-
              ter. This sequence may either be a pair of apostro-
              phe 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.)

Chat Version 1.17          27 Sep 1997                          7

CHAT(8)                                                   CHAT(8)

       \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 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 charac-
              ters 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.)

       The chat program will terminate with the following comple-
       tion codes.

       0      The normal termination of the program.  This  indi-
              cates 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 pro-
              gram. This may be due to a read or write  operation
              failing  for some reason or chat receiving a signal

Chat Version 1.17          27 Sep 1997                          8

CHAT(8)                                                   CHAT(8)

              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 program the script  correctly
              for the condition or that some unexpected event has
              occurred and  the  expected  string  could  not  be

       4      The  first  string  marked  as  an  ABORT condition

       5      The second string  marked  as  an  ABORT  condition

       6      The  third  string  marked  as  an  ABORT condition

       7      The fourth string  marked  as  an  ABORT  condition

       ...    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.

       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 pro-

       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

Chat Version 1.17          27 Sep 1997                          9

Source: OpenBSD 2.6 man pages. Copyright: Portions are copyrighted by BERKELEY
SOFTWARE DESIGN, INC., The Regents of the University of California, Massachusetts
Institute of Technology, Free Software Foundation, FreeBSD Inc., and others.

(Corrections, notes, and links courtesy of RocketAware.com)

[Detailed Topics]
FreeBSD Sources for chat(8)
OpenBSD sources for chat(8)

[Overview Topics]

Up to: Communication Scripting - Methods of " scripting " a communication connection. Sequencing and handshaking based on replies, et al.

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