2 .\" manual page [] for chat 1.8
3 .\" $Id: chat.8,v 1.7 1998/02/04 01:35:49 paulus Exp $
5 .\" SS subsection heading
7 .\" IP indented paragraph
9 .TH CHAT 8 "27 Sep 1997" "Chat Version 1.17"
11 chat \- Automated conversational script with a modem
20 The \fIchat\fR program defines a conversational exchange between the
21 computer and the modem. Its primary purpose is to establish the
22 connection between the Point-to-Point Protocol Daemon (\fIpppd\fR) and
23 the remote's \fIpppd\fR process.
27 Read the chat script from the chat \fIfile\fR. The use of this option
28 is mutually exclusive with the chat script parameters. The user must
29 have read access to the file. Multiple lines are permitted in the
30 file. Space or horizontal tab characters should be used to separate
34 Set the timeout for the expected string to be received. If the string
35 is not received within the time limit then the reply string is not
36 sent. An alternate reply may be sent or the script will fail if there
37 is no alternate reply string. A failed script will cause the
38 \fIchat\fR program to terminate with a non-zero error code.
40 .B -r \fI<report file>
41 Set the file for output of the report strings. If you use the keyword
42 \fIREPORT\fR, the resulting strings are written to this file. If this
43 option is not used and you still use \fIREPORT\fR keywords, the
44 \fIstderr\fR file is used for the report strings.
47 Start with the echo option turned on. Echoing may also be turned on
48 or off at specific points in the chat script by using the \fIECHO\fR
49 keyword. When echoing is enabled, all output from the modem is echoed
53 Request that the \fIchat\fR script be executed in a verbose mode. The
54 \fIchat\fR program will then log the execution state of the chat
55 script as well as all text received from the modem and the output
56 strings sent to the modem. The default is to log through the SYSLOG;
57 the logging method may be altered with the -S and -s flags.
60 Request that the \fIchat\fR script be executed in a stderr verbose
61 mode. The \fIchat\fR program will then log all text received from the
62 modem and the output strings sent to the modem to the stderr device. This
63 device is usually the local console at the station running the chat or
67 Use stderr. All log messages from '-v' and all error messages will be
71 Do not use the SYSLOG. By default, error messages are sent to the
72 SYSLOG. The use of -S will prevent both log messages from '-v' and
73 error messages from being sent to the SYSLOG.
75 .B -T \fI<phone number>
76 Pass in an arbitary string, usually a phone number, that will be
77 substituted for the \\T substitution metacharacter in a send string.
79 .B -U \fI<phone number 2>
80 Pass in a second string, usually a phone number, that will be
81 substituted for the \\U substitution metacharacter in a send string.
82 This is useful when dialing an ISDN terminal adapter that requires two
86 If the script is not specified in a file with the \fI-f\fR option then
87 the script is included as parameters to the \fIchat\fR program.
90 The \fIchat\fR script defines the communications.
92 A script consists of one or more "expect-send" pairs of strings,
93 separated by spaces, with an optional "subexpect-subsend" string pair,
94 separated by a dash as in the following example:
96 ogin:-BREAK-ogin: ppp ssword: hello2u2
98 This line indicates that the \fIchat\fR program should expect the string
99 "ogin:". If it fails to receive a login prompt within the time interval
100 allotted, it is to send a break sequence to the remote and then expect the
101 string "ogin:". If the first "ogin:" is received then the break sequence is
104 Once it received the login prompt the \fIchat\fR program will send the
105 string ppp and then expect the prompt "ssword:". When it receives the
106 prompt for the password, it will send the password hello2u2.
108 A carriage return is normally sent following the reply string. It is not
109 expected in the "expect" string unless it is specifically requested by using
110 the \\r character sequence.
112 The expect sequence should contain only what is needed to identify the
113 string. Since it is normally stored on a disk file, it should not contain
114 variable information. It is generally not acceptable to look for time
115 strings, network identification strings, or other variable pieces of data as
118 To help correct for characters which may be corrupted during the initial
119 sequence, look for the string "ogin:" rather than "login:". It is possible
120 that the leading "l" character may be received in error and you may never
121 find the string even though it was sent by the system. For this reason,
122 scripts look for "ogin:" rather than "login:" and "ssword:" rather than
125 A very simple script might look like this:
127 ogin: ppp ssword: hello2u2
129 In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
131 In actual practice, simple scripts are rare. At the vary least, you
132 should include sub-expect sequences should the original string not be
133 received. For example, consider the following script:
135 ogin:--ogin: ppp ssword: hello2u2
137 This would be a better script than the simple one used earlier. This would look
138 for the same login: prompt, however, if one was not received, a single
139 return sequence is sent and then it will look for login: again. Should line
140 noise obscure the first login prompt then sending the empty line will
141 usually generate a login prompt again.
143 Comments can be embedded in the chat script. A comment is a line which
144 starts with the \fB#\fR (hash) character in column 1. Such comment
145 lines are just ignored by the chat program. If a '#' character is to
146 be expected as the first character of the expect sequence, you should
147 quote the expect string.
148 If you want to wait for a prompt that starts with a # (hash)
149 character, you would have to write something like this:
151 # Now wait for the prompt and send logout string
157 Many modems will report the status of the call as a string. These
158 strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
159 is often desirable to terminate the script should the modem fail to
160 connect to the remote. The difficulty is that a script would not know
161 exactly which modem string it may receive. On one attempt, it may
162 receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
164 These "abort" strings may be specified in the script using the \fIABORT\fR
165 sequence. It is written in the script as in the following example:
167 ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
169 This sequence will expect nothing; and then send the string ATZ. The
170 expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
171 the string ATDT5551212 to dial the telephone. The expected string is
172 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
173 script is executed. However, should the modem find a busy telephone, it will
174 send the string \fIBUSY\fR. This will cause the string to match the abort
175 character sequence. The script will then fail because it found a match to
176 the abort string. If it received the string \fINO CARRIER\fR, it will abort
177 for the same reason. Either string may be received. Either string will
178 terminate the \fIchat\fR script.
179 .SH CLR_ABORT STRINGS
180 This sequence allows for clearing previously set \fBABORT\fR strings.
181 \fBABORT\fR strings are kept in an array of a pre-determined size (at
182 compilation time); \fBCLR_ABORT\fR will reclaim the space for cleared
183 entries so that new strings can use that space.
185 The \fBSAY\fR directive allows the script to send strings to the user
186 at the terminal via standard error. If \fBchat\fR is being run by
187 pppd, and pppd is running as a daemon (detached from its controlling
188 terminal), standard error will normally be redirected to the file
189 /etc/ppp/connect-errors.
191 \fBSAY\fR strings must be enclosed in single or double quotes. If
192 carriage return and line feed are needed in the string to be output,
193 you must explicitely add them to your string.
195 The SAY strings could be used to give progress messages in sections of
196 the script where you want to have 'ECHO OFF' but still let the user
197 know what is happening. An example is:
203 SAY "Dialling your ISP...\\n"
209 SAY "Waiting up to 2 minutes for connection ... "
213 SAY "Connected, now logging in ...\n"
220 SAY "Logged in OK ...\n"
223 This sequence will only present the SAY strings to the user and all
224 the details of the script will remain hidden. For example, if the
225 above script works, the user will see:
229 Waiting up to 2 minutes for connection ... Connected, now logging in ...
235 A \fBreport\fR string is similar to the ABORT string. The difference
236 is that the strings, and all characters to the next control character
237 such as a carriage return, are written to the report file.
239 The report strings may be used to isolate the transmission rate of the
240 modem's connect string and return the value to the chat user. The
241 analysis of the report string logic occurs in conjunction with the
242 other string processing such as looking for the expect string. The use
243 of the same string for a report and abort sequence is probably not
244 very useful, however, it is possible.
246 The report strings to no change the completion code of the program.
248 These "report" strings may be specified in the script using the \fIREPORT\fR
249 sequence. It is written in the script as in the following example:
251 REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
253 This sequence will expect nothing; and then send the string
254 ATDT5551212 to dial the telephone. The expected string is
255 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
256 of the script is executed. In addition the program will write to the
257 expect-file the string "CONNECT" plus any characters which follow it
258 such as the connection rate.
259 .SH CLR_REPORT STRINGS
260 This sequence allows for clearing previously set \fBREPORT\fR strings.
261 \fBREPORT\fR strings are kept in an array of a pre-determined size (at
262 compilation time); \fBCLR_REPORT\fR will reclaim the space for cleared
263 entries so that new strings can use that space.
265 The echo options controls whether the output from the modem is echoed
266 to \fIstderr\fR. This option may be set with the \fI-e\fR option, but
267 it can also be controlled by the \fIECHO\fR keyword. The "expect-send"
268 pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
269 disables it. With this keyword you can select which parts of the
270 conversation should be visible. For instance, with the following
289 all output resulting from modem configuration and dialing is not visible,
290 but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
293 The HANGUP options control whether a modem hangup should be considered
294 as an error or not. This option is useful in scripts for dialling
295 systems which will hang up and call your system back. The HANGUP
296 options can be \fBON\fR or \fBOFF\fR.
298 When HANGUP is set OFF and the modem hangs up (e.g., after the first
299 stage of logging in to a callback system), \fBchat\fR will continue
300 running the script (e.g., waiting for the incoming call and second
301 stage login prompt). As soon as the incoming call is connected, you
302 should use the \fBHANGUP ON\fR directive to reinstall normal hang up
303 signal behavior. Here is an (simple) example script:
315 \'Callback login:' call_back_ID
321 \'Callback Password:' Call_back_password
331 ogin:--BREAK--ogin: real_account
336 The initial timeout value is 45 seconds. This may be changed using the \fB-t\fR
339 To change the timeout value for the next expect string, the following
342 ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2
344 This will change the timeout to 10 seconds when it expects the login:
345 prompt. The timeout is then changed to 5 seconds when it looks for the
348 The timeout, once changed, remains in effect until it is changed again.
350 The special reply string of \fIEOT\fR indicates that the chat program
351 should send an EOT character to the remote. This is normally the
352 End-of-file character sequence. A return character is not sent
355 The EOT sequence may be embedded into the send string using the
358 The special reply string of \fIBREAK\fR will cause a break condition
359 to be sent. The break is a special signal on the transmitter. The
360 normal processing on the receiver is to change the transmission rate.
361 It may be used to cycle through the available transmission rates on
362 the remote until you are able to receive a valid login prompt.
364 The break sequence may be embedded into the send string using the
367 The expect and reply strings may contain escape sequences. All of the
368 sequences are legal in the reply string. Many are legal in the expect.
369 Those which are not valid in the expect sequence are so indicated.
372 Expects or sends a null string. If you send a null string then it will still
373 send the return character. This sequence may either be a pair of apostrophe
377 represents a backspace character.
380 Suppresses the newline at the end of the reply string. This is the only
381 method to send a string without a trailing return character. It must
382 be at the end of the send string. For example,
383 the sequence hello\\c will simply send the characters h, e, l, l, o.
384 .I (not valid in expect.)
387 Delay for one second. The program uses sleep(1) which will delay to a
388 maximum of one second.
389 .I (not valid in expect.)
393 .I (not valid in expect.)
396 Send a newline or linefeed character.
399 Send a null character. The same sequence may be represented by \\0.
400 .I (not valid in expect.)
403 Pause for a fraction of a second. The delay is 1/10th of a second.
404 .I (not valid in expect.)
407 Suppress writing the string to the SYSLOG file. The string ?????? is
408 written to the log in its place.
409 .I (not valid in expect.)
412 Send or expect a carriage return.
415 Represents a space character in the string. This may be used when it
416 is not desirable to quote the strings which contains spaces. The
417 sequence 'HI TIM' and HI\\sTIM are the same.
420 Send or expect a tab character.
423 Send or expect a backslash character.
426 Collapse the octal digits (ddd) into a single ASCII character and send that
428 .I (some characters are not valid in expect.)
431 Substitute the sequence with the control character represented by C.
432 For example, the character DC1 (17) is shown as \^^Q.
433 .I (some characters are not valid in expect.)
434 .SH TERMINATION CODES
435 The \fIchat\fR program will terminate with the following completion
439 The normal termination of the program. This indicates that the script
440 was executed without error to the normal conclusion.
443 One or more of the parameters are invalid or an expect string was too
444 large for the internal buffers. This indicates that the program as not
448 An error occurred during the execution of the program. This may be due
449 to a read or write operation failing for some reason or chat receiving
450 a signal such as SIGINT.
453 A timeout event occurred when there was an \fIexpect\fR string without
454 having a "-subsend" string. This may mean that you did not program the
455 script correctly for the condition or that some unexpected event has
456 occurred and the expected string could not be found.
459 The first string marked as an \fIABORT\fR condition occurred.
462 The second string marked as an \fIABORT\fR condition occurred.
465 The third string marked as an \fIABORT\fR condition occurred.
468 The fourth string marked as an \fIABORT\fR condition occurred.
471 The other termination codes are also strings marked as an \fIABORT\fR
474 Using the termination code, it is possible to determine which event
475 terminated the script. It is possible to decide if the string "BUSY"
476 was received from the modem as opposed to "NO DIAL TONE". While the
477 first event may be retried, the second will probably have little
478 chance of succeeding during a retry.
480 Additional information about \fIchat\fR scripts may be found with UUCP
481 documentation. The \fIchat\fR script was taken from the ideas proposed
482 by the scripts used by the \fIuucico\fR program.
486 The \fIchat\fR program is in public domain. This is not the GNU public
487 license. If it breaks then you get to keep both pieces.
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