2 .\" manual page [] for chat 1.8
3 .\" $Id: chat.8,v 1.4 1996/06/26 00:51:05 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 locaiton 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 ssowrd: 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 Many modems will report the status of the call as a string. These
126 strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
127 is often desirable to terminate the script should the modem fail to
128 connect to the remote. The difficulty is that a script would not know
129 exactly which modem string it may receive. On one attempt, it may
130 receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
132 These "abort" strings may be specified in the script using the \fIABORT\fR
133 sequence. It is written in the script as in the following example:
135 ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
137 This sequence will expect nothing; and then send the string ATZ. The
138 expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
139 the string ATDT5551212 to dial the telephone. The expected string is
140 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
141 script is executed. However, should the modem find a busy telephone, it will
142 send the string \fIBUSY\fR. This will cause the string to match the abort
143 character sequence. The script will then fail because it found a match to
144 the abort string. If it received the string \fINO CARRIER\fR, it will abort
145 for the same reason. Either string may be received. Either string will
146 terminate the \fIchat\fR script.
149 A \fBreport\fR string is similar to the ABORT string. The difference
150 is that the strings, and all characters to the next control character
151 such as a carriage return, are written to the report file.
153 The report strings may be used to isolate the transmission rate of the
154 modem's connect string and return the value to the chat user. The
155 analysis of the report string logic occurs in conjunction with the
156 other string processing such as looking for the expect string. The use
157 of the same string for a report and abort sequence is probably not
158 very useful, however, it is possible.
160 The report strings to no change the completion code of the program.
162 These "report" strings may be specified in the script using the \fIREPORT\fR
163 sequence. It is written in the script as in the following example:
165 REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
167 This sequence will expect nothing; and then send the string
168 ATDT5551212 to dial the telephone. The expected string is
169 \fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
170 of the script is executed. In addition the program will write to the
171 expect-file the string "CONNECT" plus any characters which follow it
172 such as the connection rate.
174 The echo options controls whether the output from the modem is echoed
175 to \fIstderr\fR. This option may be set with the \fI-e\fR option, but
176 it can also be controlled by the \fIECHO\fR keyword. The "expect-send"
177 pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
178 disables it. With this keyword you can select which parts of the
179 conversation should be visible. For instance, with the following
198 all output resulting from modem configuration and dialing is not visible,
199 but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
202 The initial timeout value is 45 seconds. This may be changed using the \fB-t\fR
205 To change the timeout value for the next expect string, the following
208 ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assowrd: hello2u2
210 This will change the timeout to 10 seconds when it expects the login:
211 prompt. The timeout is then changed to 5 seconds when it looks for the
214 The timeout, once changed, remains in effect until it is changed again.
216 The special reply string of \fIEOT\fR indicates that the chat program
217 should send an EOT character to the remote. This is normally the
218 End-of-file character sequence. A return character is not sent
221 The EOT sequence may be embedded into the send string using the
224 The special reply string of \fIBREAK\fR will cause a break condition
225 to be sent. The break is a special signal on the transmitter. The
226 normal processing on the receiver is to change the transmission rate.
227 It may be used to cycle through the available transmission rates on
228 the remote until you are able to receive a valid login prompt.
230 The break sequence may be embedded into the send string using the
233 The expect and reply strings may contain escape sequences. All of the
234 sequences are legal in the reply string. Many are legal in the expect.
235 Those which are not valid in the expect sequence are so indicated.
238 Expects or sends a null string. If you send a null string then it will still
239 send the return character. This sequence may either be a pair of apostrophe
243 represents a backspace character.
246 Suppresses the newline at the end of the reply string. This is the only
247 method to send a string without a trailing return character. It must
248 be at the end of the send string. For example,
249 the sequence hello\\c will simply send the characters h, e, l, l, o.
250 .I (not valid in expect.)
253 Delay for one second. The program uses sleep(1) which will delay to a
254 maximum of one second.
255 .I (not valid in expect.)
259 .I (not valid in expect.)
262 Send a newline or linefeed character.
265 Send a null character. The same sequence may be represented by \\0.
266 .I (not valid in expect.)
269 Pause for a fraction of a second. The delay is 1/10th of a second.
270 .I (not valid in expect.)
273 Suppress writing the string to the SYSLOG file. The string ?????? is
274 written to the log in its place.
275 .I (not valid in expect.)
278 Send or expect a carriage return.
281 Represents a space character in the string. This may be used when it
282 is not desirable to quote the strings which contains spaces. The
283 sequence 'HI TIM' and HI\\sTIM are the same.
286 Send or expect a tab character.
289 Send or expect a backslash character.
292 Collapse the octal digits (ddd) into a single ASCII character and send that
294 .I (some characters are not valid in expect.)
297 Substitute the sequence with the control character represented by C.
298 For example, the character DC1 (17) is shown as \^^Q.
299 .I (some characters are not valid in expect.)
300 .SH TERMINATION CODES
301 The \fIchat\fR program will terminate with the following completion
305 The normal termination of the program. This indicates that the script
306 was executed without error to the normal conclusion.
309 One or more of the parameters are invalid or an expect string was too
310 large for the internal buffers. This indicates that the program as not
314 An error occurred during the execution of the program. This may be due
315 to a read or write operation failing for some reason or chat receiving
316 a signal such as SIGINT.
319 A timeout event occurred when there was an \fIexpect\fR string without
320 having a "-subsend" string. This may mean that you did not program the
321 script correctly for the condition or that some unexpected event has
322 occurred and the expected string could not be found.
325 The first string marked as an \fIABORT\fR condition occurred.
328 The second string marked as an \fIABORT\fR condition occurred.
331 The third string marked as an \fIABORT\fR condition occurred.
334 The fourth string marked as an \fIABORT\fR condition occurred.
337 The other termination codes are also strings marked as an \fIABORT\fR
340 Using the termination code, it is possible to determine which event
341 terminated the script. It is possible to decide if the string "BUSY"
342 was received from the modem as opposed to "NO DIAL TONE". While the
343 first event may be retried, the second will probably have little
344 chance of succeeding during a retry.
346 Additional information about \fIchat\fR scripts may be found with UUCP
347 documentation. The \fIchat\fR script was taken from the ideas proposed
348 by the scripts used by the \fIuucico\fR program.
352 The \fIchat\fR program is in public domain. This is not the GNU public
353 license. If it breaks then you get to keep both pieces.
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