CHAT(8)                   (22 May 1999)                   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 estab-
          lish the connection between the Point-to-Point Protocol Dae-
          mon (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 hor-
               izontal 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 writ-
               ten 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

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               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 metacharac-
               ter 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

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          the string ppp and then expect the prompt "ssword:". When it
          receives the prompt for the password, it will send the pass-
          word 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 gen-
          erally 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 ear-
          lier. 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)

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          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 exam-
          ple, 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

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          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 differ-
          ence 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.

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          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) mes-
          sage, 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

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          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. 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.

     SENDING EOT
          The special reply string of EOT indicates that the chat pro-
          gram should send an EOT character to the remote. This is
          normally the End-of-file character sequence. A return char-
          acter 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 condi-
          tion to be sent. The break is a special signal on the trans-
          mitter. 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.

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     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 repre-
               sented 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.)

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          \\   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 rep-
               resented by C.  For example, the character DC1 (17) is
               shown as ^Q.  (some characters are not valid in

     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 envi-
          ronment variable to substitute. If the substitution fails,
          because the requested environment variable is not set, noth-
          ing is replaced for the variable.

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

          0    The normal termination of the program. This indicates
               that the script was executed without error to the nor-
               mal 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 SIG-
               INT.

          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

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               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.

     SEE ALSO
          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)

     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.

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