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CHAT(8)			    System Manager's Manual		       CHAT(8)

NAME
       chat -- Automated conversational	script with a modem

SYNOPSIS
       chat   [-eSsVv]	[-f  chat-file]	 [-r  report-file]  [-T	 phone-number]
	    [-t	timeout] [-U phone-number2] [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
       -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.

       -f chat-file
	       Read  the  chat script from the chat file.  The use of this op-
	       tion 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.

       -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.

       -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).

       -s      Use stderr.  All	log messages from -v and  all  error  messages
	       will be sent to stderr.

       -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.

       -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.

       -U phone-number2
	       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.

       -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.

       -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.

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	inter-
       val allotted, it	is to send a break sequence to the remote and then ex-
       pect  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 "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
       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
	     $ 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	 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.
       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.

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
	       character.   It must be at the end of the send string.  For ex-
	       ample, 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
	       second (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
	       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).

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 with-
	       out having a "-subsend" string.	This may mean that you did not
	       program the script correctly for	the condition or that some un-
	       expected	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.

       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.

FreeBSD	14.3		      September	10, 2012		       CHAT(8)

Want to link to this manual page? Use this URL:
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