chat man page on Archlinux

Man page or keyword search:  
man Server   11224 pages
apropos Keyword Search (all sections)
Output format
Archlinux logo
[printable version]

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

       -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

       -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  out‐
	      put  strings  sent  to the modem.	 The default is to log through
	      the SYSLOG; the logging method may be altered with the -S and -s

       -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

       -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,	 sepa‐
       rated by spaces, with an optional "subexpect-subsend" string pair, sep‐
       arated 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 con‐
       tain 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  ini‐
       tial  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

       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 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

       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 pro‐
       gram, 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 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:


       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 CON‐
       NECT. 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  charac‐
       ter 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 ter‐
       minate 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 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:

	      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  log‐
	      ging in ...
	      Logged in OK ...

       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 anal‐
       ysis  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 use‐
       ful, 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:

       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	 addi‐
       tion  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 compi‐
       lation 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'
	      ''      ATZ
	      OK\r\n  ATD1234567
	      \r\n    \c
	      ECHO    ON
	      CONNECT \c
	      ogin:   account

       all output resulting from modem configuration and dialing is not	 visi‐
       ble,  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 sys‐
       tems 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
	      ABORT "Bad Login"
	      'Callback Password:' Call_back_password
	      TIMEOUT 120
	      CONNECT \c
	      HANGUP ON
	      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 pro‐
       cessing	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  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 char‐
	      acter. 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  sec‐
	      ond.  (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

       \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

       ^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  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.

       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 pro‐
	      gram the script correctly for the condition or that  some	 unex‐
	      pected  event  has occurred and the expected string could not be

       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

       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 docu‐
       mentation. 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)

List of man pages available for Archlinux

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
Vote for polarhome
Free Shell Accounts :: the biggest list on the net