Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
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  be-
       tween  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.

       -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
	      syslog(3);  the logging method may be altered with the -S	and -s
	      flags.  Logging is done to the local2 facility at	level info for
	      verbose tracing and level	err for	some errors.

       -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 de-
	      vice.  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 syslog(3).  By	default, error messages	 are  sent  to
	      syslog(3).   The	use  of	-S will	prevent	both log messages from
	      '-v' and error messages from being sent to syslog(3).

       -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,	 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 se-
       quence 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 "ss-
       word:" 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 re-
       ceived, a single	return sequence	is sent	and then it will look for  lo-
       gin:  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 ex-
       pect 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

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 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
       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
	      $	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 ...

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: ac-
	      count

       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.

CLR_REPORT STRINGS
       This sequence allows for	clearing previously set	REPORT	strings.   RE-
       PORT strings are	kept in	an array of a pre-determined size (at compila-
       tion 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 en-
       ables echoing, and ECHO OFF disables it.	 With this keyword you can se-
       lect  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	 visi-
       ble,  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 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 a (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 se-
       quence ^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  ei-
	      ther 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 de-
	      lay 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 syslogd(8).  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.

       \\     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  ex-
	      pect.)

       ^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.)

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 pro-
	      gram the script correctly	for the	condition or that  some	 unex-
	      pected  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 docu-
       mentation.  The chat script was taken from the ideas  proposed  by  the
       scripts used by the uucico program.

       uucico(1), uucp(1), syslog(3), syslogd(8).

COPYRIGHT
       The  chat  program is in	public domain.	This is	not the	GNU public li-
       cense.  If it breaks then you get to keep both pieces.

Chat Version 1.17		  27 Sep 1997			       CHAT(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CHAT SCRIPT | COMMENTS | ABORT STRINGS | CLR_ABORT STRINGS | SAY STRINGS | REPORT STRINGS | CLR_REPORT STRINGS | ECHO | HANGUP | TIMEOUT | SENDING EOT | GENERATING BREAK | ESCAPE SEQUENCES | TERMINATION CODES | SEE ALSO | COPYRIGHT

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=chat&sektion=8&manpath=FreeBSD+8.0-RELEASE>

home | help