2 .\" manual page [] for chat 1.8
3 .\" $Id: chat.8,v 1.6 1997/11/27 06:00:06 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
64 pppd program. This option will not work properly if the stderr is
65 redirected to the /dev/null location as is the case should pppd be run
66 in the 'detached' mode. In that case, use the '-v' option to record
67 the session on the SYSLOG device.
70 Use stderr. All log messages from '-v' and all error messages will be
74 Do not use the SYSLOG. By default, error messages are sent to the
75 SYSLOG. The use of -S will prevent both log messages from '-v' and
76 error messages from being sent to the SYSLOG.
78 .B -T \fI<phone number>
79 Pass in an arbitary string, usually a phone number, that will be
80 substituted for the \\T substitution metacharacter in a send string.
82 .B -U \fI<phone number 2>
83 Pass in a second string, usually a phone number, that will be
84 substituted for the \\U substitution metacharacter in a send string.
85 This is useful when dialing an ISDN terminal adapter that requires two
89 If the script is not specified in a file with the \fI-f\fR option then
90 the script is included as parameters to the \fIchat\fR program.
93 The \fIchat\fR script defines the communications.
95 A script consists of one or more "expect-send" pairs of strings,
96 separated by spaces, with an optional "subexpect-subsend" string pair,
97 separated by a dash as in the following example:
99 ogin:-BREAK-ogin: ppp ssword: hello2u2
101 This line indicates that the \fIchat\fR program should expect the string
102 "ogin:". If it fails to receive a login prompt within the time interval
103 allotted, it is to send a break sequence to the remote and then expect the
104 string "ogin:". If the first "ogin:" is received then the break sequence is
107 Once it received the login prompt the \fIchat\fR program will send the
108 string ppp and then expect the prompt "ssword:". When it receives the
109 prompt for the password, it will send the password hello2u2.
111 A carriage return is normally sent following the reply string. It is not
112 expected in the "expect" string unless it is specifically requested by using
113 the \\r character sequence.
115 The expect sequence should contain only what is needed to identify the
116 string. Since it is normally stored on a disk file, it should not contain
117 variable information. It is generally not acceptable to look for time
118 strings, network identification strings, or other variable pieces of data as
121 To help correct for characters which may be corrupted during the initial
122 sequence, look for the string "ogin:" rather than "login:". It is possible
123 that the leading "l" character may be received in error and you may never
124 find the string even though it was sent by the system. For this reason,
125 scripts look for "ogin:" rather than "login:" and "ssword:" rather than
128 A very simple script might look like this:
130 ogin: ppp ssword: hello2u2
132 In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
134 In actual practice, simple scripts are rare. At the vary least, you
135 should include sub-expect sequences should the original string not be
136 received. For example, consider the following script:
138 ogin:--ogin: ppp ssword: hello2u2
140 This would be a better script than the simple one used earlier. This would look
141 for the same login: prompt, however, if one was not received, a single
142 return sequence is sent and then it will look for login: again. Should line
143 noise obscure the first login prompt then sending the empty line will
144 usually generate a login prompt again.
146 Comments can be embedded in the chat script. A comment is a line which
147 starts with the \fB#\fR (hash) character in column 1. Such comment
148 lines are just ignored by the chat program. If a '#' character is to
149 be expected as the first character of the expect sequence, you should
150 quote the expect string.
151 If you want to wait for a prompt that starts with a # (hash)
152 character, you would have to write something like this:
154 # Now wait for the prompt and send logout string
160 Many modems will report the status of the call as a string. These
161 strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
162 is often desirable to terminate the script should the modem fail to
163 connect to the remote. The difficulty is that a script would not know
164 exactly which modem string it may receive. On one attempt, it may
165 receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
167 These "abort" strings may be specified in the script using the \fIABORT\fR
168 sequence. It is written in the script as in the following example:
170 ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
172 This sequence will expect nothing; and then send the string ATZ. The
173 expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
174 the string ATDT5551212 to dial the telephone. The expected string is
175 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
176 script is executed. However, should the modem find a busy telephone, it will
177 send the string \fIBUSY\fR. This will cause the string to match the abort
178 character sequence. The script will then fail because it found a match to
179 the abort string. If it received the string \fINO CARRIER\fR, it will abort
180 for the same reason. Either string may be received. Either string will
181 terminate the \fIchat\fR script.
182 .SH CLR_ABORT STRINGS
183 This sequence allows for clearing previously set \fBABORT\fR strings.
184 \fBABORT\fR strings are kept in an array of a pre-determined size (at
185 compilation time); \fBCLR_ABORT\fR will reclaim the space for cleared
186 entries so that new strings can use that space.
188 The \fBSAY\fR directive allows the script to send strings to the user
189 at the terminal via standard error. If \fBchat\fR is being run by
190 pppd, and pppd is running as a daemon (detached from its controlling
191 terminal), standard error will normally be redirected to the file
192 /etc/ppp/connect-errors.
194 \fBSAY\fR strings must be enclosed in single or double quotes. If
195 carriage return and line feed are needed in the string to be output,
196 you must explicitely add them to your string.
198 The SAY strings could be used to give progress messages in sections of
199 the script where you want to have 'ECHO OFF' but still let the user
200 know what is happening. An example is:
206 SAY "Dialling your ISP...\\n"
212 SAY "Waiting up to 2 minutes for connection ... "
216 SAY "Connected, now logging in ...\n"
223 SAY "Logged in OK ...\n"
226 This sequence will only present the SAY strings to the user and all
227 the details of the script will remain hidden. For example, if the
228 above script works, the user will see:
232 Waiting up to 2 minutes for connection ... Connected, now logging in ...
238 A \fBreport\fR string is similar to the ABORT string. The difference
239 is that the strings, and all characters to the next control character
240 such as a carriage return, are written to the report file.
242 The report strings may be used to isolate the transmission rate of the
243 modem's connect string and return the value to the chat user. The
244 analysis of the report string logic occurs in conjunction with the
245 other string processing such as looking for the expect string. The use
246 of the same string for a report and abort sequence is probably not
247 very useful, however, it is possible.
249 The report strings to no change the completion code of the program.
251 These "report" strings may be specified in the script using the \fIREPORT\fR
252 sequence. It is written in the script as in the following example:
254 REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
256 This sequence will expect nothing; and then send the string
257 ATDT5551212 to dial the telephone. The expected string is
258 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
259 of the script is executed. In addition the program will write to the
260 expect-file the string "CONNECT" plus any characters which follow it
261 such as the connection rate.
262 .SH CLR_REPORT STRINGS
263 This sequence allows for clearing previously set \fBREPORT\fR strings.
264 \fBREPORT\fR strings are kept in an array of a pre-determined size (at
265 compilation time); \fBCLR_REPORT\fR will reclaim the space for cleared
266 entries so that new strings can use that space.
268 The echo options controls whether the output from the modem is echoed
269 to \fIstderr\fR. This option may be set with the \fI-e\fR option, but
270 it can also be controlled by the \fIECHO\fR keyword. The "expect-send"
271 pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
272 disables it. With this keyword you can select which parts of the
273 conversation should be visible. For instance, with the following
292 all output resulting from modem configuration and dialing is not visible,
293 but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
296 The HANGUP options control whether a modem hangup should be considered
297 as an error or not. This option is useful in scripts for dialling
298 systems which will hang up and call your system back. The HANGUP
299 options can be \fBON\fR or \fBOFF\fR.
301 When HANGUP is set OFF and the modem hangs up (e.g., after the first
302 stage of logging in to a callback system), \fBchat\fR will continue
303 running the script (e.g., waiting for the incoming call and second
304 stage login prompt). As soon as the incoming call is connected, you
305 should use the \fBHANGUP ON\fR directive to reinstall normal hang up
306 signal behavior. Here is an (simple) example script:
318 \'Callback login:' call_back_ID
324 \'Callback Password:' Call_back_password
334 ogin:--BREAK--ogin: real_account
339 The initial timeout value is 45 seconds. This may be changed using the \fB-t\fR
342 To change the timeout value for the next expect string, the following
345 ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2
347 This will change the timeout to 10 seconds when it expects the login:
348 prompt. The timeout is then changed to 5 seconds when it looks for the
351 The timeout, once changed, remains in effect until it is changed again.
353 The special reply string of \fIEOT\fR indicates that the chat program
354 should send an EOT character to the remote. This is normally the
355 End-of-file character sequence. A return character is not sent
358 The EOT sequence may be embedded into the send string using the
361 The special reply string of \fIBREAK\fR will cause a break condition
362 to be sent. The break is a special signal on the transmitter. The
363 normal processing on the receiver is to change the transmission rate.
364 It may be used to cycle through the available transmission rates on
365 the remote until you are able to receive a valid login prompt.
367 The break sequence may be embedded into the send string using the
370 The expect and reply strings may contain escape sequences. All of the
371 sequences are legal in the reply string. Many are legal in the expect.
372 Those which are not valid in the expect sequence are so indicated.
375 Expects or sends a null string. If you send a null string then it will still
376 send the return character. This sequence may either be a pair of apostrophe
380 represents a backspace character.
383 Suppresses the newline at the end of the reply string. This is the only
384 method to send a string without a trailing return character. It must
385 be at the end of the send string. For example,
386 the sequence hello\\c will simply send the characters h, e, l, l, o.
387 .I (not valid in expect.)
390 Delay for one second. The program uses sleep(1) which will delay to a
391 maximum of one second.
392 .I (not valid in expect.)
396 .I (not valid in expect.)
399 Send a newline or linefeed character.
402 Send a null character. The same sequence may be represented by \\0.
403 .I (not valid in expect.)
406 Pause for a fraction of a second. The delay is 1/10th of a second.
407 .I (not valid in expect.)
410 Suppress writing the string to the SYSLOG file. The string ?????? is
411 written to the log in its place.
412 .I (not valid in expect.)
415 Send or expect a carriage return.
418 Represents a space character in the string. This may be used when it
419 is not desirable to quote the strings which contains spaces. The
420 sequence 'HI TIM' and HI\\sTIM are the same.
423 Send or expect a tab character.
426 Send or expect a backslash character.
429 Collapse the octal digits (ddd) into a single ASCII character and send that
431 .I (some characters are not valid in expect.)
434 Substitute the sequence with the control character represented by C.
435 For example, the character DC1 (17) is shown as \^^Q.
436 .I (some characters are not valid in expect.)
437 .SH TERMINATION CODES
438 The \fIchat\fR program will terminate with the following completion
442 The normal termination of the program. This indicates that the script
443 was executed without error to the normal conclusion.
446 One or more of the parameters are invalid or an expect string was too
447 large for the internal buffers. This indicates that the program as not
451 An error occurred during the execution of the program. This may be due
452 to a read or write operation failing for some reason or chat receiving
453 a signal such as SIGINT.
456 A timeout event occurred when there was an \fIexpect\fR string without
457 having a "-subsend" string. This may mean that you did not program the
458 script correctly for the condition or that some unexpected event has
459 occurred and the expected string could not be found.
462 The first string marked as an \fIABORT\fR condition occurred.
465 The second string marked as an \fIABORT\fR condition occurred.
468 The third string marked as an \fIABORT\fR condition occurred.
471 The fourth string marked as an \fIABORT\fR condition occurred.
474 The other termination codes are also strings marked as an \fIABORT\fR
477 Using the termination code, it is possible to determine which event
478 terminated the script. It is possible to decide if the string "BUSY"
479 was received from the modem as opposed to "NO DIAL TONE". While the
480 first event may be retried, the second will probably have little
481 chance of succeeding during a retry.
483 Additional information about \fIchat\fR scripts may be found with UUCP
484 documentation. The \fIchat\fR script was taken from the ideas proposed
485 by the scripts used by the \fIuucico\fR program.
489 The \fIchat\fR program is in public domain. This is not the GNU public
490 license. If it breaks then you get to keep both pieces.
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