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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  Protocol  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 permit-ted permitted
              ted 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 key-words, keywords,
              words, 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 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 strings sent to the modem  to  the  stderr
              device.  This device is usually the local console at the station running the chat or pppd pro-gram. 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 sub-stitution substitution
              stitution 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 substitu-tion substitution
              tion  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 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 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

       To help correct for characters which may be corrupted during  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,  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  usu-ally usually
       ally generate a login prompt again.

       Comments can be embedded in the chat script. A comment is a line which starts with the # (hash) char-acter character
       acter 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  some-thing something
       thing 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 program, 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 CAR-RIER CARRIER
       RIER 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
       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  termi-nal), terminal),
       nal), 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 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:

              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 ...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 logging in ...
              Logged in OK ...

       A report string is similar to the ABORT string. The difference is that the strings, and  all  charac-ters characters
       ters 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  exe-cuted. executed.
       cuted. In addition 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 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 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'
              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 CON-NECT CONNECT
       NECT (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  call-back callback
       back  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  direc-tive directive
       tive 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 ...

       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

       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

       ''     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 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

       \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.

       \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 expect.)

       ^C     Substitute the sequence with the control character represented by C.  For example, the charac-ter character
              ter 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 com-mand command
       mand line. The metacharacter $ is used to introduce the name of the environment variable  to  substi-tute. substitute.
       tute.  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 program the script correctly for the  condition  or  that  some
              unexpected 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 pos-sible possible
       sible 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

       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 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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