2 .\" manual page [] for chat 1.8
3 .\" $Id: chat.8,v 1.11 2004/11/13 12:22:49 paulus Exp $
5 .\" SS subsection heading
7 .\" IP indented paragraph
9 .TH CHAT 8 "22 May 1999" "Chat Version 1.22"
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 Enables environment variable substitution within chat scripts using the
54 standard \fI$xxx\fR syntax.
57 Request that the \fIchat\fR script be executed in a verbose mode. The
58 \fIchat\fR program will then log the execution state of the chat
59 script as well as all text received from the modem and the output
60 strings sent to the modem. The default is to log through the SYSLOG;
61 the logging method may be altered with the \-S and \-s flags.
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
75 Do not use the SYSLOG. By default, error messages are sent to the
76 SYSLOG. The use of \-S will prevent both log messages from '\-v' and
77 error messages from being sent to the SYSLOG.
79 .B \-T \fI<phone number>
80 Pass in an arbitrary string, usually a phone number, that will be
81 substituted for the \\T substitution metacharacter in a send string.
83 .B \-U \fI<phone number 2>
84 Pass in a second string, usually a phone number, that will be
85 substituted for the \\U substitution metacharacter in a send string.
86 This is useful when dialing an ISDN terminal adapter that requires two
90 If the script is not specified in a file with the \fI\-f\fR option then
91 the script is included as parameters to the \fIchat\fR program.
94 The \fIchat\fR script defines the communications.
96 A script consists of one or more "expect\-send" pairs of strings,
97 separated by spaces, with an optional "subexpect\-subsend" string pair,
98 separated by a dash as in the following example:
100 ogin:\-BREAK\-ogin: ppp ssword: hello2u2
102 This line indicates that the \fIchat\fR program should expect the string
103 "ogin:". If it fails to receive a login prompt within the time interval
104 allotted, it is to send a break sequence to the remote and then expect the
105 string "ogin:". If the first "ogin:" is received then the break sequence is
108 Once it received the login prompt the \fIchat\fR program will send the
109 string ppp and then expect the prompt "ssword:". When it receives the
110 prompt for the password, it will send the password hello2u2.
112 A carriage return is normally sent following the reply string. It is not
113 expected in the "expect" string unless it is specifically requested by using
114 the \\r character sequence.
116 The expect sequence should contain only what is needed to identify the
117 string. Since it is normally stored on a disk file, it should not contain
118 variable information. It is generally not acceptable to look for time
119 strings, network identification strings, or other variable pieces of data as
122 To help correct for characters which may be corrupted during the initial
123 sequence, look for the string "ogin:" rather than "login:". It is possible
124 that the leading "l" character may be received in error and you may never
125 find the string even though it was sent by the system. For this reason,
126 scripts look for "ogin:" rather than "login:" and "ssword:" rather than
129 A very simple script might look like this:
131 ogin: ppp ssword: hello2u2
133 In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
135 In actual practice, simple scripts are rare. At the vary least, you
136 should include sub-expect sequences should the original string not be
137 received. For example, consider the following script:
139 ogin:\-\-ogin: ppp ssword: hello2u2
141 This would be a better script than the simple one used earlier. This would look
142 for the same login: prompt, however, if one was not received, a single
143 return sequence is sent and then it will look for login: again. Should line
144 noise obscure the first login prompt then sending the empty line will
145 usually generate a login prompt again.
147 Comments can be embedded in the chat script. A comment is a line which
148 starts with the \fB#\fR (hash) character in column 1. Such comment
149 lines are just ignored by the chat program. If a '#' character is to
150 be expected as the first character of the expect sequence, you should
151 quote the expect string.
152 If you want to wait for a prompt that starts with a # (hash)
153 character, you would have to write something like this:
155 # Now wait for the prompt and send logout string
160 .SH SENDING DATA FROM A FILE
161 If the string to send starts with an at sign (@), the rest of the
162 string is taken to be the name of a file to read to get the string to
163 send. If the last character of the data read is a newline, it is
164 removed. The file can be a named pipe (or fifo) instead of a regular
165 file. This provides a way for \fBchat\fR to communicate with another
166 program, for example, a program to prompt the user and receive a
171 Many modems will report the status of the call as a string. These
172 strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
173 is often desirable to terminate the script should the modem fail to
174 connect to the remote. The difficulty is that a script would not know
175 exactly which modem string it may receive. On one attempt, it may
176 receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
178 These "abort" strings may be specified in the script using the \fIABORT\fR
179 sequence. It is written in the script as in the following example:
181 ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
183 This sequence will expect nothing; and then send the string ATZ. The
184 expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
185 the string ATDT5551212 to dial the telephone. The expected string is
186 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
187 script is executed. However, should the modem find a busy telephone, it will
188 send the string \fIBUSY\fR. This will cause the string to match the abort
189 character sequence. The script will then fail because it found a match to
190 the abort string. If it received the string \fINO CARRIER\fR, it will abort
191 for the same reason. Either string may be received. Either string will
192 terminate the \fIchat\fR script.
193 .SH CLR_ABORT STRINGS
194 This sequence allows for clearing previously set \fBABORT\fR strings.
195 \fBABORT\fR strings are kept in an array of a pre-determined size (at
196 compilation time); \fBCLR_ABORT\fR will reclaim the space for cleared
197 entries so that new strings can use that space.
199 The \fBSAY\fR directive allows the script to send strings to the user
200 at the terminal via standard error. If \fBchat\fR is being run by
201 pppd, and pppd is running as a daemon (detached from its controlling
202 terminal), standard error will normally be redirected to the file
203 /etc/ppp/connect\-errors.
205 \fBSAY\fR strings must be enclosed in single or double quotes. If
206 carriage return and line feed are needed in the string to be output,
207 you must explicitly add them to your string.
209 The SAY strings could be used to give progress messages in sections of
210 the script where you want to have 'ECHO OFF' but still let the user
211 know what is happening. An example is:
217 SAY "Dialling your ISP...\\n"
223 SAY "Waiting up to 2 minutes for connection ... "
227 SAY "Connected, now logging in ...\\n"
235 SAY "Logged in OK ...\\n"
238 This sequence will only present the SAY strings to the user and all
239 the details of the script will remain hidden. For example, if the
240 above script works, the user will see:
244 Waiting up to 2 minutes for connection ... Connected, now logging in ...
250 A \fBreport\fR string is similar to the ABORT string. The difference
251 is that the strings, and all characters to the next control character
252 such as a carriage return, are written to the report file.
254 The report strings may be used to isolate the transmission rate of the
255 modem's connect string and return the value to the chat user. The
256 analysis of the report string logic occurs in conjunction with the
257 other string processing such as looking for the expect string. The use
258 of the same string for a report and abort sequence is probably not
259 very useful, however, it is possible.
261 The report strings to no change the completion code of the program.
263 These "report" strings may be specified in the script using the \fIREPORT\fR
264 sequence. It is written in the script as in the following example:
266 REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
268 This sequence will expect nothing; and then send the string
269 ATDT5551212 to dial the telephone. The expected string is
270 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
271 of the script is executed. In addition the program will write to the
272 expect\-file the string "CONNECT" plus any characters which follow it
273 such as the connection rate.
274 .SH CLR_REPORT STRINGS
275 This sequence allows for clearing previously set \fBREPORT\fR strings.
276 \fBREPORT\fR strings are kept in an array of a pre-determined size (at
277 compilation time); \fBCLR_REPORT\fR will reclaim the space for cleared
278 entries so that new strings can use that space.
280 The echo options controls whether the output from the modem is echoed
281 to \fIstderr\fR. This option may be set with the \fI\-e\fR option, but
282 it can also be controlled by the \fIECHO\fR keyword. The "expect\-send"
283 pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
284 disables it. With this keyword you can select which parts of the
285 conversation should be visible. For instance, with the following
304 all output resulting from modem configuration and dialing is not visible,
305 but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
308 The HANGUP options control whether a modem hangup should be considered
309 as an error or not. This option is useful in scripts for dialling
310 systems which will hang up and call your system back. The HANGUP
311 options can be \fBON\fR or \fBOFF\fR.
313 When HANGUP is set OFF and the modem hangs up (e.g., after the first
314 stage of logging in to a callback system), \fBchat\fR will continue
315 running the script (e.g., waiting for the incoming call and second
316 stage login prompt). As soon as the incoming call is connected, you
317 should use the \fBHANGUP ON\fR directive to reinstall normal hang up
318 signal behavior. Here is an (simple) example script:
330 \&'Callback login:' call_back_ID
336 \&'Callback Password:' Call_back_password
346 ogin:\-\-BREAK\-\-ogin: real_account
351 The initial timeout value is 45 seconds. This may be changed using the \fB\-t\fR
354 To change the timeout value for the next expect string, the following
357 ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:\-\-ogin: TIMEOUT 5 assword: hello2u2
359 This will change the timeout to 10 seconds when it expects the login:
360 prompt. The timeout is then changed to 5 seconds when it looks for the
363 The timeout, once changed, remains in effect until it is changed again.
365 The special reply string of \fIEOT\fR indicates that the chat program
366 should send an EOT character to the remote. This is normally the
367 End-of-file character sequence. A return character is not sent
369 The EOT sequence may be embedded into the send string using the
372 The special reply string of \fIBREAK\fR will cause a break condition
373 to be sent. The break is a special signal on the transmitter. The
374 normal processing on the receiver is to change the transmission rate.
375 It may be used to cycle through the available transmission rates on
376 the remote until you are able to receive a valid login prompt.
377 The break sequence may be embedded into the send string using the
380 The expect and reply strings may contain escape sequences. All of the
381 sequences are legal in the reply string. Many are legal in the expect.
382 Those which are not valid in the expect sequence are so indicated.
385 Expects or sends a null string. If you send a null string then it will still
386 send the return character. This sequence may either be a pair of apostrophe
390 represents a backspace character.
393 Suppresses the newline at the end of the reply string. This is the only
394 method to send a string without a trailing return character. It must
395 be at the end of the send string. For example,
396 the sequence hello\\c will simply send the characters h, e, l, l, o.
397 .I (not valid in expect.)
400 Delay for one second. The program uses sleep(1) which will delay to a
401 maximum of one second.
402 .I (not valid in expect.)
406 .I (not valid in expect.)
409 Send a newline or linefeed character.
412 Send a null character. The same sequence may be represented by \\0.
413 .I (not valid in expect.)
416 Pause for a fraction of a second. The delay is 1/10th of a second.
417 .I (not valid in expect.)
420 Suppress writing the string to the SYSLOG file. The string ?????? is
421 written to the log in its place.
422 .I (not valid in expect.)
425 Send or expect a carriage return.
428 Represents a space character in the string. This may be used when it
429 is not desirable to quote the strings which contains spaces. The
430 sequence 'HI TIM' and HI\\sTIM are the same.
433 Send or expect a tab character.
436 Send the phone number string as specified with the \fI\-T\fR option
437 .I (not valid in expect.)
440 Send the phone number 2 string as specified with the \fI\-U\fR option
441 .I (not valid in expect.)
444 Send or expect a backslash character.
447 Collapse the octal digits (ddd) into a single ASCII character and send that
449 .I (some characters are not valid in expect.)
452 Substitute the sequence with the control character represented by C.
453 For example, the character DC1 (17) is shown as \^^Q.
454 .I (some characters are not valid in expect.)
455 .SH ENVIRONMENT VARIABLES
456 Environment variables are available within chat scripts, if the \fI\-E\fR
457 option was specified in the command line. The metacharacter \fI$\fR is used
458 to introduce the name of the environment variable to substitute. If the
459 substitution fails, because the requested environment variable is not set,
460 \fInothing\fR is replaced for the variable.
461 .SH TERMINATION CODES
462 The \fIchat\fR program will terminate with the following completion
466 The normal termination of the program. This indicates that the script
467 was executed without error to the normal conclusion.
470 One or more of the parameters are invalid or an expect string was too
471 large for the internal buffers. This indicates that the program as not
475 An error occurred during the execution of the program. This may be due
476 to a read or write operation failing for some reason or chat receiving
477 a signal such as SIGINT.
480 A timeout event occurred when there was an \fIexpect\fR string without
481 having a "\-subsend" string. This may mean that you did not program the
482 script correctly for the condition or that some unexpected event has
483 occurred and the expected string could not be found.
486 The first string marked as an \fIABORT\fR condition occurred.
489 The second string marked as an \fIABORT\fR condition occurred.
492 The third string marked as an \fIABORT\fR condition occurred.
495 The fourth string marked as an \fIABORT\fR condition occurred.
498 The other termination codes are also strings marked as an \fIABORT\fR
501 Using the termination code, it is possible to determine which event
502 terminated the script. It is possible to decide if the string "BUSY"
503 was received from the modem as opposed to "NO DIAL TONE". While the
504 first event may be retried, the second will probably have little
505 chance of succeeding during a retry.
507 Additional information about \fIchat\fR scripts may be found with UUCP
508 documentation. The \fIchat\fR script was taken from the ideas proposed
509 by the scripts used by the \fIuucico\fR program.
513 The \fIchat\fR program is in public domain. This is not the GNU public
514 license. If it breaks then you get to keep both pieces.
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