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CHAT(8)                                                                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 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 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.

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 "subex-
       pect-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  diffi-
       culty 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 tele-
       phone, 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 /var/log/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  hid-
       den. 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 con-
       nection 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  echo-
       ing, and ECHO OFF disables it. With this keyword you can select which parts of the conversation should be visi-
       ble. 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.

HANGUP
       The HANGUP options control whether a modem hangup should be considered as an error or not.  This option is use-
       ful 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 sig-
       nal 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 ...


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  substition
       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.

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.



Chat Version 1.22                 22 May 1999                          CHAT(8)