476 lines
17 KiB
Groff
476 lines
17 KiB
Groff
.\" -*- nroff -*-
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.\" manual page [] for chat 1.8
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.\" $Id: chat.8,v 1.8 1997/02/22 19:54:22 peter 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 "5 May 1995" "Chat Version 1.9"
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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 -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 -r \fI<report file>
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Set the file for output of the report strings. If you use the keyword
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\fIREPORT\fR, the resulting strings are written to this file. If this
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option is not used and you still use \fIREPORT\fR keywords, the
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\fIstderr\fR file is used for the report strings.
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.TP
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.B -e
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Start with the echo option turned on. Echoing may also be turned on
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or off at specific points in the chat script by using the \fIECHO\fR
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keyword. When echoing is enabled, all output from the modem is echoed
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to \fIstderr\fR.
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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
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.IR syslogd (8).
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Logging is
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done to the \fIlocal2\fR facility at level \fIinfo\fR for verbose tracing
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and level \fIerr\fR for some errors.
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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 stderr verbose
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mode. The \fIchat\fR program will then log all text received from the
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modem and the output strings which it sends to the stderr device. This
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device is usually the local console at the station running the chat or
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pppd program. This option will not work properly if the stderr is
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redirected to the /dev/null location as is the case should pppd be run
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in the 'detached' mode. In that case, use the '-v' option to record
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the session on the SYSLOG device.
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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
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string ppp and then expect the prompt "ssword:". When it receives the
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prompt for the 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 ssword: 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 COMMENTS
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Comments can be embedded in the chat script. A comment is a line which
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starts with the \fB#\fR (hash) character in column 1. Such comment
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lines are just ignored by the chat program. If a '#' character is to
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be expected as the first character of the expect sequence, you should
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quote the expect string.
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If you want to wait for a prompt that starts with a # (hash)
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character, you would have to write something like this:
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.IP
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# Now wait for the prompt and send logout string
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.br
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\'# ' logout
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.LP
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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 CLR_ABORT STRINGS
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This sequence allows for clearing previously set \fBABORT\fR strings.
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\fBABORT\fR strings are kept in an array of a pre-determined size (at
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compilation time); \fBCLR_ABORT\fR will reclaim the space for cleared
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entries so that new strings can use that space.
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.SH SAY STRINGS
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The \fBSAY\fR directive allows the script to send strings to the user
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at the terminal via standard error. If \fBchat\fR is being run by
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pppd, and pppd is running as a daemon (detached from its controlling
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terminal), standard error will normally be redirected to the file
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/etc/ppp/connect-errors.
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.LP
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\fBSAY\fR strings must be enclosed in single or double quotes. If
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carriage return and line feed are needed in the string to be output,
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you must explicitely add them to your string.
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.LP
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The SAY strings could be used to give progress messages in sections of
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the script where you want to have 'ECHO OFF' but still let the user
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know what is happening. An example is:
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.IP
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ABORT BUSY
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.br
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ECHO OFF
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.br
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SAY "Dialling your ISP...\\n"
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.br
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\'' ATDT5551212
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.br
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TIMEOUT 120
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.br
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SAY "Waiting up to 2 minutes for connection ... "
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.br
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CONNECT ''
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.br
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SAY "Connected, now logging in ...\n"
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.br
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ogin: account
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.br
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ssword: pass
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.br
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$ \c
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SAY "Logged in OK ...\n"
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\fIetc ...\fR
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.LP
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This sequence will only present the SAY strings to the user and all
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the details of the script will remain hidden. For example, if the
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above script works, the user will see:
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.IP
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Dialling your ISP...
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.br
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Waiting up to 2 minutes for connection ... Connected, now logging in ...
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.br
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Logged in OK ...
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.LP
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.SH REPORT STRINGS
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A \fBreport\fR string is similar to the ABORT string. The difference
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is that the strings, and all characters to the next control character
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such as a carriage return, are written to the report file.
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.LP
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The report strings may be used to isolate the transmission rate of the
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modem's connect string and return the value to the chat user. The
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analysis of the report string logic occurs in conjunction with the
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other string processing such as looking for the expect string. The use
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of the same string for a report and abort sequence is probably not
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very useful, however, it is possible.
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.LP
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The report strings to no change the completion code of the program.
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.LP
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These "report" strings may be specified in the script using the \fIREPORT\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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REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
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.LP
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This sequence will expect nothing; and then send the string
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ATDT5551212 to dial the telephone. The expected string is
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\fICONNECT\fR. If the string \fICONNECT\fR is received the remainder
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of the script is executed. In addition the program will write to the
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expect-file the string "CONNECT" plus any characters which follow it
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such as the connection rate.
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.SH CLR_REPORT STRINGS
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This sequence allows for clearing previously set \fBREPORT\fR strings.
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\fBREPORT\fR strings are kept in an array of a pre-determined size (at
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compilation time); \fBCLR_REPORT\fR will reclaim the space for cleared
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entries so that new strings can use that space.
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.SH ECHO
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The echo options controls whether the output from the modem is echoed
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to \fIstderr\fR. This option may be set with the \fI-e\fR option, but
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it can also be controlled by the \fIECHO\fR keyword. The "expect-send"
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pair \fIECHO\fR \fION\fR enables echoing, and \fIECHO\fR \fIOFF\fR
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disables it. With this keyword you can select which parts of the
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conversation should be visible. For instance, with the following
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script:
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.IP
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ABORT 'BUSY'
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.br
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ABORT 'NO CARRIER'
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.br
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'' ATZ
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.br
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OK\\r\\n ATD1234567
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.br
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\\r\\n \\c
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.br
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ECHO ON
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.br
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CONNECT \\c
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.br
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ogin: account
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.LP
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all output resulting from modem configuration and dialing is not visible,
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but starting with the \fICONNECT\fR (or \fIBUSY\fR) message, everything
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will be echoed.
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.SH HANGUP
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The HANGUP options control whether a modem hangup should be considered
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as an error or not. This option is useful in scripts for dialling
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systems which will hang up and call your system back. The HANGUP
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options can be \fBON\fR or \fBOFF\fR.
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.br
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When HANGUP is set OFF and the modem hangs up (e.g., after the first
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stage of logging in to a callback system), \fBchat\fR will continue
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running the script (e.g., waiting for the incoming call and second
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stage login prompt). As soon as the incoming call is connected, you
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should use the \fBHANGUP ON\fR directive to reinstall normal hang up
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signal behavior. Here is an (simple) example script:
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.IP
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ABORT 'BUSY'
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.br
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'' ATZ
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.br
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OK\\r\\n ATD1234567
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.br
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\\r\\n \\c
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.br
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CONNECT \\c
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.br
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\'Callback login:' call_back_ID
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.br
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HANGUP OFF
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.br
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ABORT "Bad Login"
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.br
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\'Callback Password:' Call_back_password
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.br
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TIMEOUT 120
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.br
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CONNECT \\c
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.br
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HANGUP ON
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.br
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ABORT "NO CARRIER"
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.br
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ogin:--BREAK--ogin: real_account
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.br
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\fIetc ...\fR
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.LP
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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 assword: 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
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.IR syslogd (8).
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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 TERMINATION CODES
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The \fIchat\fR program will terminate with the following completion
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codes.
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.TP
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.B 0
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The normal termination of the program. This indicates that the script
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was executed without error to the normal conclusion.
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.TP
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.B 1
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One or more of the parameters are invalid or an expect string was too
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large for the internal buffers. This indicates that the program as not
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properly executed.
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.TP
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.B 2
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An error occurred during the execution of the program. This may be due
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to a read or write operation failing for some reason or chat receiving
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a signal such as SIGINT.
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.TP
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.B 3
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A timeout event occurred when there was an \fIexpect\fR string without
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having a "-subsend" string. This may mean that you did not program the
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script correctly for the condition or that some unexpected event has
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occurred and the expected string could not be found.
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.TP
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.B 4
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The first string marked as an \fIABORT\fR condition occurred.
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.TP
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.B 5
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The second string marked as an \fIABORT\fR condition occurred.
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.TP
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.B 6
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The third string marked as an \fIABORT\fR condition occurred.
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.TP
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.B 7
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The fourth string marked as an \fIABORT\fR condition occurred.
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.TP
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.B ...
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The other termination codes are also strings marked as an \fIABORT\fR
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condition.
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.LP
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Using the termination code, it is possible to determine which event
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terminated the script. It is possible to decide if the string "BUSY"
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was received from the modem as opposed to "NO DIAL TONE". While the
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first event may be retried, the second will probably have little
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chance of succeeding during a retry.
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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
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by the 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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