252 lines
9.6 KiB
Groff
252 lines
9.6 KiB
Groff
.\" -*- nroff -*-
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.\" manual page [] for chat 1.8
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.\" $Id: chat.8,v 1.7 1994/03/04 20:19:30 callahan Exp $
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.\" SH section heading
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.\" SS subsection heading
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.\" LP paragraph
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.\" IP indented paragraph
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.\" TP hanging label
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.TH CHAT 8 "17 April 1994" "Chat Version 1.8"
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.SH NAME
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chat \- Automated conversational script with a modem
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.SH SYNOPSIS
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.B chat
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[
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.I options
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]
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.I script
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.SH DESCRIPTION
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.LP
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The \fIchat\fR program defines a conversational exchange between the
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computer and the modem. Its primary purpose is to establish the
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connection between the Point-to-Point Protocol Daemon (\fIpppd\fR) and
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the remote's \fIpppd\fR process.
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.SH OPTIONS
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.TP
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.B -f \fI<chat file>
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Read the chat script from the chat \fIfile\fR. The use of this option
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is mutually exclusive with the chat script parameters. The user must
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have read access to the file. Multiple lines are permitted in the
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file. Space or horizontal tab characters should be used to separate
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the strings.
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.TP
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.B -l \fI<lock file>
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Perform the UUCP style locking using the indicated lock file.
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.IP
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If the file could not be created then the \fIchat\fR program will
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fail. The lock file will be deleted only if the \fIchat\fR program
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fails to perform the script for any reason. If the script is
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successful the lock file will be left on the disk. It is expected that
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the lock file will be deleted when the \fIpppd\fR process no longer
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wishes to use the serial device.
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.IP
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The use of a lock file with
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.I chat
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and
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\fIpppd\fR\'s
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.I lock
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option should not be used at the same time. They are mutually
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exclusive options and will cause one or the other program to fail to
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achieve the required lock if you use both.
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.TP
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.B -t \fI<timeout>
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Set the timeout for the expected string to be received. If the string
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is not received within the time limit then the reply string is not
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sent. An alternate reply may be sent or the script will fail if there
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is no alternate reply string. A failed script will cause the
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\fIchat\fR program to terminate with a non-zero error code.
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.TP
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.B -v
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Request that the \fIchat\fR script be executed in a verbose mode. The
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\fIchat\fR program will then log all text received from the modem and
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the output strings which it sends to the SYSLOG.
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.TP
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.B script
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If the script is not specified in a file with the \fI-f\fR option then
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the script is included as parameters to the \fIchat\fR program.
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.SH CHAT SCRIPT
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.LP
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The \fIchat\fR script defines the communications.
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.LP
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A script consists of one or more "expect-send" pairs of strings,
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separated by spaces, with an optional "subexpect-subsend" string pair,
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separated by a dash as in the following example:
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.IP
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ogin:-BREAK-ogin: ppp ssword: hello2u2
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.LP
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This line indicates that the \fIchat\fR program should expect the string
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"ogin:". If it fails to receive a login prompt within the time interval
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allotted, it is to send a break sequence to the remote and then expect the
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string "ogin:". If the first "ogin:" is received then the break sequence is
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not generated.
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.LP
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Once it received the login prompt the \fIchat\fR program will send the string ppp
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and then expect the prompt "ssword:". When it receives the prompt for the
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password, it will send the password hello2u2.
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.LP
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A carriage return is normally sent following the reply string. It is not
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expected in the "expect" string unless it is specifically requested by using
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the \\r character sequence.
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.LP
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The expect sequence should contain only what is needed to identify the
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string. Since it is normally stored on a disk file, it should not contain
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variable information. It is generally not acceptable to look for time
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strings, network identification strings, or other variable pieces of data as
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an expect string.
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.LP
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To help correct for characters which may be corrupted during the initial
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sequence, look for the string "ogin:" rather than "login:". It is possible
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that the leading "l" character may be received in error and you may never
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find the string even though it was sent by the system. For this reason,
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scripts look for "ogin:" rather than "login:" and "ssword:" rather than
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"password:".
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.LP
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A very simple script might look like this:
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.IP
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ogin: ppp ssword: hello2u2
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.LP
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In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
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.LP
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In actual practice, simple scripts are rare. At the vary least, you
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should include sub-expect sequences should the original string not be
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received. For example, consider the following script:
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.IP
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ogin:--ogin: ppp ssowrd: hello2u2
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.LP
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This would be a better script than the simple one used earlier. This would look
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for the same login: prompt, however, if one was not received, a single
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return sequence is sent and then it will look for login: again. Should line
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noise obscure the first login prompt then sending the empty line will
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usually generate a login prompt again.
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.SH ABORT STRINGS
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Many modems will report the status of the call as a string. These
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strings may be \fBCONNECTED\fR or \fBNO CARRIER\fR or \fBBUSY\fR. It
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is often desirable to terminate the script should the modem fail to
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connect to the remote. The difficulty is that a script would not know
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exactly which modem string it may receive. On one attempt, it may
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receive \fBBUSY\fR while the next time it may receive \fBNO CARRIER\fR.
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.LP
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These "abort" strings may be specified in the script using the \fIABORT\fR
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sequence. It is written in the script as in the following example:
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.IP
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ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
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.LP
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This sequence will expect nothing; and then send the string ATZ. The
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expected response to this is the string \fIOK\fR. When it receives \fIOK\fR,
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the string ATDT5551212 to dial the telephone. The expected string is
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\fICONNECT\fR. If the string \fICONNECT\fR is received the remainder of the
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script is executed. However, should the modem find a busy telephone, it will
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send the string \fIBUSY\fR. This will cause the string to match the abort
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character sequence. The script will then fail because it found a match to
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the abort string. If it received the string \fINO CARRIER\fR, it will abort
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for the same reason. Either string may be received. Either string will
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terminate the \fIchat\fR script.
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.SH TIMEOUT
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The initial timeout value is 45 seconds. This may be changed using the \fB-t\fR
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parameter.
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.LP
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To change the timeout value for the next expect string, the following
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example may be used:
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.IP
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ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assowrd: hello2u2
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.LP
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This will change the timeout to 10 seconds when it expects the login:
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prompt. The timeout is then changed to 5 seconds when it looks for the
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password prompt.
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.LP
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The timeout, once changed, remains in effect until it is changed again.
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.SH SENDING EOT
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The special reply string of \fIEOT\fR indicates that the chat program
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should send an EOT character to the remote. This is normally the
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End-of-file character sequence. A return character is not sent
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following the EOT.
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.PR
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The EOT sequence may be embedded into the send string using the
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sequence \fI^D\fR.
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.SH GENERATING BREAK
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The special reply string of \fIBREAK\fR will cause a break condition
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to be sent. The break is a special signal on the transmitter. The
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normal processing on the receiver is to change the transmission rate.
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It may be used to cycle through the available transmission rates on
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the remote until you are able to receive a valid login prompt.
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.PR
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The break sequence may be embedded into the send string using the
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\fI\\K\fR sequence.
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.SH ESCAPE SEQUENCES
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The expect and reply strings may contain escape sequences. All of the
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sequences are legal in the reply string. Many are legal in the expect.
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Those which are not valid in the expect sequence are so indicated.
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.TP
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.B ''
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Expects or sends a null string. If you send a null string then it will still
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send the return character. This sequence may either be a pair of apostrophe
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or quote characters.
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.TP
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.B \\\\b
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represents a backspace character.
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.TP
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.B \\\\c
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Suppresses the newline at the end of the reply string. This is the only
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method to send a string without a trailing return character. It must
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be at the end of the send string. For example,
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the sequence hello\\c will simply send the characters h, e, l, l, o.
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.I (not valid in expect.)
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.TP
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.B \\\\d
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Delay for one second. The program uses sleep(1) which will delay to a
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maximum of one second.
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.I (not valid in expect.)
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.TP
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.B \\\\K
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Insert a BREAK
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.I (not valid in expect.)
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.TP
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.B \\\\n
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Send a newline or linefeed character.
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.TP
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.B \\\\N
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Send a null character. The same sequence may be represented by \\0.
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.I (not valid in expect.)
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.TP
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.B \\\\p
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Pause for a fraction of a second. The delay is 1/10th of a second.
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.I (not valid in expect.)
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.TP
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.B \\\\q
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Suppress writing the string to the SYSLOG file. The string ?????? is
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written to the log in its place.
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.I (not valid in expect.)
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.TP
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.B \\\\r
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Send or expect a carriage return.
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.TP
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.B \\\\s
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Represents a space character in the string. This may be used when it
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is not desirable to quote the strings which contains spaces. The
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sequence 'HI TIM' and HI\\sTIM are the same.
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.TP
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.B \\\\t
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Send or expect a tab character.
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.TP
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.B \\\\\\\\
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Send or expect a backslash character.
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.TP
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.B \\\\ddd
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Collapse the octal digits (ddd) into a single ASCII character and send that
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character.
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.I (some characters are not valid in expect.)
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.TP
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.B \^^C
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Substitute the sequence with the control character represented by C.
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For example, the character DC1 (17) is shown as \^^Q.
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.I (some characters are not valid in expect.)
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.SH SEE ALSO
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Additional information about \fIchat\fR scripts may be found with UUCP
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documentation. The \fIchat\fR script was taken from the ideas proposed by the
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scripts used by the \fIuucico\fR program.
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.LP
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uucico(1), uucp(1)
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.SH COPYRIGHT
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The \fIchat\fR program is in public domain. This is not the GNU public
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license. If it breaks then you get to keep both pieces.
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