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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
	      code.  You  can  also use the TIMEOUT string in order to specify
	      the timeout.

       -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 ...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'
	      ''      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. You can also specify "TIMEOUT 0".

       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

       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)

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