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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.

       -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
              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 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
              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,
       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 string.

       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 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

SENDING DATA FROM A FILE
       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.

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
       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.

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
              $ \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
              logging 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
       addition 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
       compilation 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
       visible, 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 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 ...

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
              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.)

       \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 character DC1 (17) is shown as ^Q.
              (some characters are not valid in expect.)

ENVIRONMENT VARIABLES
       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.

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
              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 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.

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 1.22                 22 May 1999                          CHAT(8)