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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.

       -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
	      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 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

       -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

       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 ...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 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'
	      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'
	      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 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

       ^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.)

       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), syslog(3), syslogd(8).

       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 1.17		  27 Sep 1997			       CHAT(8)


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