2 .\" manual page [] for chat 1.8
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
58 the logging method may be altered with the -S and -s flags.
60 done to the \fIlocal2\fR facility at level \fIinfo\fR for verbose tracing
61 and level \fIerr\fR for some errors.
64 Request that the \fIchat\fR script be executed in a stderr verbose
65 mode. The \fIchat\fR program will then log all text received from the
66 modem and the output strings sent to the modem to the stderr device. This
67 device is usually the local console at the station running the chat or
71 Use stderr. All log messages from '-v' and all error messages will be
77 By default, error messages are sent to
79 The use of -S will prevent both log messages from '-v' and
80 error messages from being sent to
83 .B -T \fI<phone number>
84 Pass in an arbitrary string, usually a phone number, that will be
85 substituted for the \\T substitution metacharacter in a send string.
87 .B -U \fI<phone number 2>
88 Pass in a second string, usually a phone number, that will be
89 substituted for the \\U substitution metacharacter in a send string.
90 This is useful when dialing an ISDN terminal adapter that requires two
94 If the script is not specified in a file with the \fI-f\fR option then
95 the script is included as parameters to the \fIchat\fR program.
98 The \fIchat\fR script defines the communications.
100 A script consists of one or more "expect-send" pairs of strings,
101 separated by spaces, with an optional "subexpect-subsend" string pair,
102 separated by a dash as in the following example:
104 ogin:-BREAK-ogin: ppp ssword: hello2u2
106 This line indicates that the \fIchat\fR program should expect the string
107 "ogin:". If it fails to receive a login prompt within the time interval
108 allotted, it is to send a break sequence to the remote and then expect the
109 string "ogin:". If the first "ogin:" is received then the break sequence is
112 Once it received the login prompt the \fIchat\fR program will send the
113 string ppp and then expect the prompt "ssword:". When it receives the
114 prompt for the password, it will send the password hello2u2.
116 A carriage return is normally sent following the reply string. It is not
117 expected in the "expect" string unless it is specifically requested by using
118 the \\r character sequence.
120 The expect sequence should contain only what is needed to identify the
121 string. Since it is normally stored on a disk file, it should not contain
122 variable information. It is generally not acceptable to look for time
123 strings, network identification strings, or other variable pieces of data as
126 To help correct for characters which may be corrupted during the initial
127 sequence, look for the string "ogin:" rather than "login:". It is possible
128 that the leading "l" character may be received in error and you may never
129 find the string even though it was sent by the system. For this reason,
130 scripts look for "ogin:" rather than "login:" and "ssword:" rather than
133 A very simple script might look like this:
135 ogin: ppp ssword: hello2u2
137 In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
139 In actual practice, simple scripts are rare. At the vary least, you
140 should include sub-expect sequences should the original string not be
141 received. For example, consider the following script:
143 ogin:--ogin: ppp ssword: hello2u2
145 This would be a better script than the simple one used earlier. This would look
146 for the same login: prompt, however, if one was not received, a single
147 return sequence is sent and then it will look for login: again. Should line
148 noise obscure the first login prompt then sending the empty line will
149 usually generate a login prompt again.
151 Comments can be embedded in the chat script. A comment is a line which
152 starts with the \fB#\fR (hash) character in column 1. Such comment
153 lines are just ignored by the chat program. If a '#' character is to
154 be expected as the first character of the expect sequence, you should
155 quote the expect string.
156 If you want to wait for a prompt that starts with a # (hash)
157 character, you would have to write something like this:
159 # Now wait for the prompt and send logout string
165 Many modems will report the status of the call as a string. These
166 strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
167 is often desirable to terminate the script should the modem fail to
168 connect to the remote. The difficulty is that a script would not know
169 exactly which modem string it may receive. On one attempt, it may
170 receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
172 These "abort" strings may be specified in the script using the \fIABORT\fR
173 sequence. It is written in the script as in the following example:
175 ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
177 This sequence will expect nothing; and then send the string ATZ. The
178 expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
179 the string ATDT5551212 to dial the telephone. The expected string is
180 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
181 script is executed. However, should the modem find a busy telephone, it will
182 send the string \fIBUSY\fR. This will cause the string to match the abort
183 character sequence. The script will then fail because it found a match to
184 the abort string. If it received the string \fINO CARRIER\fR, it will abort
185 for the same reason. Either string may be received. Either string will
186 terminate the \fIchat\fR script.
187 .SH CLR_ABORT STRINGS
188 This sequence allows for clearing previously set \fBABORT\fR strings.
189 \fBABORT\fR strings are kept in an array of a pre-determined size (at
190 compilation time); \fBCLR_ABORT\fR will reclaim the space for cleared
191 entries so that new strings can use that space.
193 The \fBSAY\fR directive allows the script to send strings to the user
194 at the terminal via standard error. If \fBchat\fR is being run by
195 pppd, and pppd is running as a daemon (detached from its controlling
196 terminal), standard error will normally be redirected to the file
197 /etc/ppp/connect-errors.
199 \fBSAY\fR strings must be enclosed in single or double quotes. If
200 carriage return and line feed are needed in the string to be output,
201 you must explicitly add them to your string.
203 The SAY strings could be used to give progress messages in sections of
204 the script where you want to have 'ECHO OFF' but still let the user
205 know what is happening. An example is:
211 SAY "Dialling your ISP...\\n"
217 SAY "Waiting up to 2 minutes for connection ... "
221 SAY "Connected, now logging in ...\n"
228 SAY "Logged in OK ...\n"
231 This sequence will only present the SAY strings to the user and all
232 the details of the script will remain hidden. For example, if the
233 above script works, the user will see:
237 Waiting up to 2 minutes for connection ... Connected, now logging in ...
243 A \fBreport\fR string is similar to the ABORT string. The difference
244 is that the strings, and all characters to the next control character
245 such as a carriage return, are written to the report file.
247 The report strings may be used to isolate the transmission rate of the
248 modem's connect string and return the value to the chat user. The
249 analysis of the report string logic occurs in conjunction with the
250 other string processing such as looking for the expect string. The use
251 of the same string for a report and abort sequence is probably not
252 very useful, however, it is possible.
254 The report strings to no change the completion code of the program.
256 These "report" strings may be specified in the script using the \fIREPORT\fR
257 sequence. It is written in the script as in the following example:
259 REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
261 This sequence will expect nothing; and then send the string
262 ATDT5551212 to dial the telephone. The expected string is
263 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
264 of the script is executed. In addition the program will write to the
265 expect-file the string "CONNECT" plus any characters which follow it
266 such as the connection rate.
267 .SH CLR_REPORT STRINGS
268 This sequence allows for clearing previously set \fBREPORT\fR strings.
269 \fBREPORT\fR strings are kept in an array of a pre-determined size (at
270 compilation time); \fBCLR_REPORT\fR will reclaim the space for cleared
271 entries so that new strings can use that space.
273 The echo options controls whether the output from the modem is echoed
274 to \fIstderr\fR. This option may be set with the \fI-e\fR option, but
275 it can also be controlled by the \fIECHO\fR keyword. The "expect-send"
276 pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
277 disables it. With this keyword you can select which parts of the
278 conversation should be visible. For instance, with the following
297 all output resulting from modem configuration and dialing is not visible,
298 but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
301 The HANGUP options control whether a modem hangup should be considered
302 as an error or not. This option is useful in scripts for dialling
303 systems which will hang up and call your system back. The HANGUP
304 options can be \fBON\fR or \fBOFF\fR.
306 When HANGUP is set OFF and the modem hangs up (e.g., after the first
307 stage of logging in to a callback system), \fBchat\fR will continue
308 running the script (e.g., waiting for the incoming call and second
309 stage login prompt). As soon as the incoming call is connected, you
310 should use the \fBHANGUP ON\fR directive to reinstall normal hang up
311 signal behavior. Here is an (simple) example script:
323 \'Callback login:' call_back_ID
329 \'Callback Password:' Call_back_password
339 ogin:--BREAK--ogin: real_account
344 The initial timeout value is 45 seconds. This may be changed using the \fB-t\fR
347 To change the timeout value for the next expect string, the following
350 ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2
352 This will change the timeout to 10 seconds when it expects the login:
353 prompt. The timeout is then changed to 5 seconds when it looks for the
356 The timeout, once changed, remains in effect until it is changed again.
358 The special reply string of \fIEOT\fR indicates that the chat program
359 should send an EOT character to the remote. This is normally the
360 End-of-file character sequence. A return character is not sent
363 The EOT sequence may be embedded into the send string using the
366 The special reply string of \fIBREAK\fR will cause a break condition
367 to be sent. The break is a special signal on the transmitter. The
368 normal processing on the receiver is to change the transmission rate.
369 It may be used to cycle through the available transmission rates on
370 the remote until you are able to receive a valid login prompt.
372 The break sequence may be embedded into the send string using the
375 The expect and reply strings may contain escape sequences. All of the
376 sequences are legal in the reply string. Many are legal in the expect.
377 Those which are not valid in the expect sequence are so indicated.
380 Expects or sends a null string. If you send a null string then it will still
381 send the return character. This sequence may either be a pair of apostrophe
385 represents a backspace character.
388 Suppresses the newline at the end of the reply string. This is the only
389 method to send a string without a trailing return character. It must
390 be at the end of the send string. For example,
391 the sequence hello\\c will simply send the characters h, e, l, l, o.
392 .I (not valid in expect.)
395 Delay for one second. The program uses sleep(1) which will delay to a
396 maximum of one second.
397 .I (not valid in expect.)
401 .I (not valid in expect.)
404 Send a newline or linefeed character.
407 Send a null character. The same sequence may be represented by \\0.
408 .I (not valid in expect.)
411 Pause for a fraction of a second. The delay is 1/10th of a second.
412 .I (not valid in expect.)
415 Suppress writing the string to
418 written to the log in its place.
419 .I (not valid in expect.)
422 Send or expect a carriage return.
425 Represents a space character in the string. This may be used when it
426 is not desirable to quote the strings which contains spaces. The
427 sequence 'HI TIM' and HI\\sTIM are the same.
430 Send or expect a tab character.
433 Send or expect a backslash character.
436 Collapse the octal digits (ddd) into a single ASCII character and send that
438 .I (some characters are not valid in expect.)
441 Substitute the sequence with the control character represented by C.
442 For example, the character DC1 (17) is shown as \^^Q.
443 .I (some characters are not valid in expect.)
444 .SH TERMINATION CODES
445 The \fIchat\fR program will terminate with the following completion
449 The normal termination of the program. This indicates that the script
450 was executed without error to the normal conclusion.
453 One or more of the parameters are invalid or an expect string was too
454 large for the internal buffers. This indicates that the program as not
458 An error occurred during the execution of the program. This may be due
459 to a read or write operation failing for some reason or chat receiving
460 a signal such as SIGINT.
463 A timeout event occurred when there was an \fIexpect\fR string without
464 having a "-subsend" string. This may mean that you did not program the
465 script correctly for the condition or that some unexpected event has
466 occurred and the expected string could not be found.
469 The first string marked as an \fIABORT\fR condition occurred.
472 The second string marked as an \fIABORT\fR condition occurred.
475 The third string marked as an \fIABORT\fR condition occurred.
478 The fourth string marked as an \fIABORT\fR condition occurred.
481 The other termination codes are also strings marked as an \fIABORT\fR
484 Using the termination code, it is possible to determine which event
485 terminated the script. It is possible to decide if the string "BUSY"
486 was received from the modem as opposed to "NO DIAL TONE". While the
487 first event may be retried, the second will probably have little
488 chance of succeeding during a retry.
490 Additional information about \fIchat\fR scripts may be found with UUCP
491 documentation. The \fIchat\fR script was taken from the ideas proposed
492 by the scripts used by the \fIuucico\fR program.
494 uucico(1), uucp(1), syslog(3), syslogd(8).
496 The \fIchat\fR program is in public domain. This is not the GNU public
497 license. If it breaks then you get to keep both pieces.
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