2 .\" manual page [] for chat 1.8
3 .\" $Id: chat.8,v 1.5 1997/07/14 03:49:41 paulus Exp $
5 .\" SS subsection heading
7 .\" IP indented paragraph
9 .TH CHAT 8 "5 May 1995" "Chat Version 1.9"
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 all text received from the modem and
55 the output strings which it sends to the SYSLOG.
58 Request that the \fIchat\fR script be executed in a stderr verbose
59 mode. The \fIchat\fR program will then log all text received from the
60 modem and the output strings which it sends to the stderr device. This
61 device is usually the local console at the station running the chat or
62 pppd program. This option will not work properly if the stderr is
63 redirected to the /dev/null location as is the case should pppd be run
64 in the 'detached' mode. In that case, use the '-v' option to record
65 the session on the SYSLOG device.
68 If the script is not specified in a file with the \fI-f\fR option then
69 the script is included as parameters to the \fIchat\fR program.
72 The \fIchat\fR script defines the communications.
74 A script consists of one or more "expect-send" pairs of strings,
75 separated by spaces, with an optional "subexpect-subsend" string pair,
76 separated by a dash as in the following example:
78 ogin:-BREAK-ogin: ppp ssword: hello2u2
80 This line indicates that the \fIchat\fR program should expect the string
81 "ogin:". If it fails to receive a login prompt within the time interval
82 allotted, it is to send a break sequence to the remote and then expect the
83 string "ogin:". If the first "ogin:" is received then the break sequence is
86 Once it received the login prompt the \fIchat\fR program will send the
87 string ppp and then expect the prompt "ssword:". When it receives the
88 prompt for the password, it will send the password hello2u2.
90 A carriage return is normally sent following the reply string. It is not
91 expected in the "expect" string unless it is specifically requested by using
92 the \\r character sequence.
94 The expect sequence should contain only what is needed to identify the
95 string. Since it is normally stored on a disk file, it should not contain
96 variable information. It is generally not acceptable to look for time
97 strings, network identification strings, or other variable pieces of data as
100 To help correct for characters which may be corrupted during the initial
101 sequence, look for the string "ogin:" rather than "login:". It is possible
102 that the leading "l" character may be received in error and you may never
103 find the string even though it was sent by the system. For this reason,
104 scripts look for "ogin:" rather than "login:" and "ssword:" rather than
107 A very simple script might look like this:
109 ogin: ppp ssword: hello2u2
111 In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
113 In actual practice, simple scripts are rare. At the vary least, you
114 should include sub-expect sequences should the original string not be
115 received. For example, consider the following script:
117 ogin:--ogin: ppp ssword: hello2u2
119 This would be a better script than the simple one used earlier. This would look
120 for the same login: prompt, however, if one was not received, a single
121 return sequence is sent and then it will look for login: again. Should line
122 noise obscure the first login prompt then sending the empty line will
123 usually generate a login prompt again.
125 Comments can be embedded in the chat script. A comment is a line which
126 starts with the \fB#\fR (hash) character in column 1. Such comment
127 lines are just ignored by the chat program. If a '#' character is to
128 be expected as the first character of the expect sequence, you should
129 quote the expect string.
130 If you want to wait for a prompt that starts with a # (hash)
131 character, you would have to write something like this:
133 # Now wait for the prompt and send logout string
139 Many modems will report the status of the call as a string. These
140 strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
141 is often desirable to terminate the script should the modem fail to
142 connect to the remote. The difficulty is that a script would not know
143 exactly which modem string it may receive. On one attempt, it may
144 receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
146 These "abort" strings may be specified in the script using the \fIABORT\fR
147 sequence. It is written in the script as in the following example:
149 ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
151 This sequence will expect nothing; and then send the string ATZ. The
152 expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
153 the string ATDT5551212 to dial the telephone. The expected string is
154 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
155 script is executed. However, should the modem find a busy telephone, it will
156 send the string \fIBUSY\fR. This will cause the string to match the abort
157 character sequence. The script will then fail because it found a match to
158 the abort string. If it received the string \fINO CARRIER\fR, it will abort
159 for the same reason. Either string may be received. Either string will
160 terminate the \fIchat\fR script.
161 .SH CLR_ABORT STRINGS
162 This sequence allows for clearing previously set \fBABORT\fR strings.
163 \fBABORT\fR strings are kept in an array of a pre-determined size (at
164 compilation time); \fBCLR_ABORT\fR will reclaim the space for cleared
165 entries so that new strings can use that space.
167 The \fBSAY\fR directive allows the script to send strings to the user
168 at the terminal via standard error. If \fBchat\fR is being run by
169 pppd, and pppd is running as a daemon (detached from its controlling
170 terminal), standard error will normally be redirected to the file
171 /etc/ppp/connect-errors.
173 \fBSAY\fR strings must be enclosed in single or double quotes. If
174 carriage return and line feed are needed in the string to be output,
175 you must explicitely add them to your string.
177 The SAY strings could be used to give progress messages in sections of
178 the script where you want to have 'ECHO OFF' but still let the user
179 know what is happening. An example is:
185 SAY "Dialling your ISP...\\n"
191 SAY "Waiting up to 2 minutes for connection ... "
195 SAY "Connected, now logging in ...\n"
202 SAY "Logged in OK ...\n"
205 This sequence will only present the SAY strings to the user and all
206 the details of the script will remain hidden. For example, if the
207 above script works, the user will see:
211 Waiting up to 2 minutes for connection ... Connected, now logging in ...
217 A \fBreport\fR string is similar to the ABORT string. The difference
218 is that the strings, and all characters to the next control character
219 such as a carriage return, are written to the report file.
221 The report strings may be used to isolate the transmission rate of the
222 modem's connect string and return the value to the chat user. The
223 analysis of the report string logic occurs in conjunction with the
224 other string processing such as looking for the expect string. The use
225 of the same string for a report and abort sequence is probably not
226 very useful, however, it is possible.
228 The report strings to no change the completion code of the program.
230 These "report" strings may be specified in the script using the \fIREPORT\fR
231 sequence. It is written in the script as in the following example:
233 REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
235 This sequence will expect nothing; and then send the string
236 ATDT5551212 to dial the telephone. The expected string is
237 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
238 of the script is executed. In addition the program will write to the
239 expect-file the string "CONNECT" plus any characters which follow it
240 such as the connection rate.
241 .SH CLR_REPORT STRINGS
242 This sequence allows for clearing previously set \fBREPORT\fR strings.
243 \fBREPORT\fR strings are kept in an array of a pre-determined size (at
244 compilation time); \fBCLR_REPORT\fR will reclaim the space for cleared
245 entries so that new strings can use that space.
247 The echo options controls whether the output from the modem is echoed
248 to \fIstderr\fR. This option may be set with the \fI-e\fR option, but
249 it can also be controlled by the \fIECHO\fR keyword. The "expect-send"
250 pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
251 disables it. With this keyword you can select which parts of the
252 conversation should be visible. For instance, with the following
271 all output resulting from modem configuration and dialing is not visible,
272 but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
275 The HANGUP options control whether a modem hangup should be considered
276 as an error or not. This option is useful in scripts for dialling
277 systems which will hang up and call your system back. The HANGUP
278 options can be \fBON\fR or \fBOFF\fR.
280 When HANGUP is set OFF and the modem hangs up (e.g., after the first
281 stage of logging in to a callback system), \fBchat\fR will continue
282 running the script (e.g., waiting for the incoming call and second
283 stage login prompt). As soon as the incoming call is connected, you
284 should use the \fBHANGUP ON\fR directive to reinstall normal hang up
285 signal behavior. Here is an (simple) example script:
297 \'Callback login:' call_back_ID
303 \'Callback Password:' Call_back_password
313 ogin:--BREAK--ogin: real_account
318 The initial timeout value is 45 seconds. This may be changed using the \fB-t\fR
321 To change the timeout value for the next expect string, the following
324 ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2
326 This will change the timeout to 10 seconds when it expects the login:
327 prompt. The timeout is then changed to 5 seconds when it looks for the
330 The timeout, once changed, remains in effect until it is changed again.
332 The special reply string of \fIEOT\fR indicates that the chat program
333 should send an EOT character to the remote. This is normally the
334 End-of-file character sequence. A return character is not sent
337 The EOT sequence may be embedded into the send string using the
340 The special reply string of \fIBREAK\fR will cause a break condition
341 to be sent. The break is a special signal on the transmitter. The
342 normal processing on the receiver is to change the transmission rate.
343 It may be used to cycle through the available transmission rates on
344 the remote until you are able to receive a valid login prompt.
346 The break sequence may be embedded into the send string using the
349 The expect and reply strings may contain escape sequences. All of the
350 sequences are legal in the reply string. Many are legal in the expect.
351 Those which are not valid in the expect sequence are so indicated.
354 Expects or sends a null string. If you send a null string then it will still
355 send the return character. This sequence may either be a pair of apostrophe
359 represents a backspace character.
362 Suppresses the newline at the end of the reply string. This is the only
363 method to send a string without a trailing return character. It must
364 be at the end of the send string. For example,
365 the sequence hello\\c will simply send the characters h, e, l, l, o.
366 .I (not valid in expect.)
369 Delay for one second. The program uses sleep(1) which will delay to a
370 maximum of one second.
371 .I (not valid in expect.)
375 .I (not valid in expect.)
378 Send a newline or linefeed character.
381 Send a null character. The same sequence may be represented by \\0.
382 .I (not valid in expect.)
385 Pause for a fraction of a second. The delay is 1/10th of a second.
386 .I (not valid in expect.)
389 Suppress writing the string to the SYSLOG file. The string ?????? is
390 written to the log in its place.
391 .I (not valid in expect.)
394 Send or expect a carriage return.
397 Represents a space character in the string. This may be used when it
398 is not desirable to quote the strings which contains spaces. The
399 sequence 'HI TIM' and HI\\sTIM are the same.
402 Send or expect a tab character.
405 Send or expect a backslash character.
408 Collapse the octal digits (ddd) into a single ASCII character and send that
410 .I (some characters are not valid in expect.)
413 Substitute the sequence with the control character represented by C.
414 For example, the character DC1 (17) is shown as \^^Q.
415 .I (some characters are not valid in expect.)
416 .SH TERMINATION CODES
417 The \fIchat\fR program will terminate with the following completion
421 The normal termination of the program. This indicates that the script
422 was executed without error to the normal conclusion.
425 One or more of the parameters are invalid or an expect string was too
426 large for the internal buffers. This indicates that the program as not
430 An error occurred during the execution of the program. This may be due
431 to a read or write operation failing for some reason or chat receiving
432 a signal such as SIGINT.
435 A timeout event occurred when there was an \fIexpect\fR string without
436 having a "-subsend" string. This may mean that you did not program the
437 script correctly for the condition or that some unexpected event has
438 occurred and the expected string could not be found.
441 The first string marked as an \fIABORT\fR condition occurred.
444 The second string marked as an \fIABORT\fR condition occurred.
447 The third string marked as an \fIABORT\fR condition occurred.
450 The fourth string marked as an \fIABORT\fR condition occurred.
453 The other termination codes are also strings marked as an \fIABORT\fR
456 Using the termination code, it is possible to determine which event
457 terminated the script. It is possible to decide if the string "BUSY"
458 was received from the modem as opposed to "NO DIAL TONE". While the
459 first event may be retried, the second will probably have little
460 chance of succeeding during a retry.
462 Additional information about \fIchat\fR scripts may be found with UUCP
463 documentation. The \fIchat\fR script was taken from the ideas proposed
464 by the scripts used by the \fIuucico\fR program.
468 The \fIchat\fR program is in public domain. This is not the GNU public
469 license. If it breaks then you get to keep both pieces.
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