CHAT(8)

NAME
chat - 与数据机自动沟通的指令稿

总览 SYNOPSIS
chat [ options ] script

描述 DESCRIPTION

chat 程式在电脑与数据机之间定义沟通交换事宜。 它最主要的 目的是用来在点对点协定的隐形程式 (pppd) 以及远端的 pppd 程序 之间建立连线。

选项 OPTIONS

-f <chat file>
    从 chat 档案读取 chat 指令稿。这个选项的使用与 chat 的 令稿参数互斥(mutually exclusive)。使用者必须具有存取该 档案的读取权。在档案中允许多线(multiple lines)设定。应 该要以空白或是横向定位(horizontal tab)字元来分隔字串。

-t <timeout>
    对于所要接收的期待字串(expected string)设定逾时限制。 如果在该时间限制内没有接收到该字串的话那么就不送出回复 字串(reply string)。 可以送出一个变通(alternate)的回复 或者如果没有变通的回复字串则该指令稿将会失败。一个失败 的指令稿将会使得 chat 程式以一个非零的错误码结束。

-r <report file>
    Set the file for output of the report strings. If you use the keyword REPORT, the resulting strings are written to this file. If this option is not used and you still use REPORT keywords, the stderr file is used for the report strings.

-e  Start with the echo option turned on. Echoing may also be turned on or off at specific points in the chat script by using the ECHO keyword. When echoing is enabled, all output from the modem is echoed to stderr.

-E  Enables environment variable substituion within chat scripts using the standard $xxx syntax.

-v  要求 chat 指令稿以冗长(verbose)模式执行。 这个 chat 程 式接下来会将所有从数据机接收的文字以及输出的字串记录到 SYSLOG 去。The default is to log through the SYSLOG; the logging method may be altered with the -S and -s flags.

-V  Request that the chat script be executed in a stderr verbose mode. The chat program will then log all text received from the modem and the output strings sent to the modem to the stderr device. This device is usually the local console at the station running the chat or pppd program.

-s  Use stderr. All log messages from '-v' and all error messages will be sent to stderr.

-S  Do not use the SYSLOG. By default, error messages are sent to the SYSLOG. The use of -S will prevent both log messages from '-v' and error messages from being sent to the SYSLOG.

-T <phone number>
    Pass in an arbitary string, usually a phone number, that will be substituted for the \T substitution metacharacter in a send string.

-U <phone number 2>
    Pass in a second string, usually a phone number, that will be substituted for the \U substitution metacharacter in a send string. This is useful when dialing an ISDN terminal adapter that requires two numbers.

script
    script 如果指令稿没有以 -f 选项指定在档案里那么该指令稿会如同 参数般被包含在 chat 程式里。

CHAT 脚本 SCRIPT

chat 脚本定义通讯过程

一个指令稿里包含一个或多个〞期待对方送出(expect-send)〞的配对 字串(pairs of string)，以空白隔开，还有一个选择性的〞期待对方 送出之候补(subexpect-subsend)〞配对字串，以短线(dash)隔开。像 下面这个例子：

    ogin:-BREAK-ogin: ppp ssword: hello2u2

这一行指示 chat 程式应该期待 "ogin:" 这个字串。如果在所分配的 时间区间内接收签入提示失败的话， 那它就送出一个中断程序(break sequence)给远端然后期待 "ogin:" 这个字串。 如果第一个 "ogin:" 被接收到那么中断程序就不会产生。

一旦它接收到该签入提示则 chat 程式将会送出 ppp 这个字串然后期 待 "ssword:" 这个提示。当它接收到密码提示以后，它将会送出密码 hello2u2 。

一般在回复字串后面会跟著送出一个机架返回(carriage return)。在 〞期待〞字串里除非以 字元程序(character sequence)指定为必 须否则不会期待它的出现。

期待程序(expect sequence)应该只包含辨认字串所需要的资料。因为 它一般是储放在磁碟档案里，它不应该包含变动的资讯。 通常以期待 字串来寻找时间字串(time strings)， 网路辨识字串(network iden- tification strings)，或是其它变动的资料是不被接受的。

为求协助修正在初始化程序中(initial sequence) 可能会传送错误的 字元，所以寻找 "ogin:" 这个字串而不是 "login:" 。 开头的 "l" 字元可能接收错误而你永远找不到该字串， 即使它已经被系统送出。 因此缘故，指令稿寻找 "ogin:" 而不是 "login:" 以及 "ssword" 而 不是 "password:" 。

一个非常简单的指令稿看起来可能像这样：

    ogin: ppp ssword: hello2u2

换句话说， 期待 ...ogin:, 送出 ppp, 期待 ...ssword:, 再送出 hello2u2 。

在实际使用上，简单的指令稿是罕见的。最少最少， 原先的字串没有 被接收时你应该要把候补期待(sub-sequences)包括进来。例如，考虑 下面这个例子：

    ogin:--ogin: ppp ssword: hello2u2

这会是一个比前面所用的简单指令稿更好的指令稿。 这个会寻找相同 同的 login: 提示，然而, 如果没有接收到的话， 会送出一个单独的 返回程序(return sequence)并且它会接著再次寻找 login: 。要是杂 杂讯掩盖掉第一个 login 提示那么接著送出空线路(empty line)经常 将会再次产生签入提示。

COMMENTS
Comments can be embedded in the chat script. A comment is a line which starts with the # (hash) character in column 1. Such comment lines are just ignored by the chat program. If a '#' character is to be expected as the first character of the expect sequence, you should quote the expect string. If you want to wait for a prompt that starts with a # (hash) character, you would have to write something like this:

    # Now wait for the prompt and send logout string
    '# ' logout

SENDING DATA FROM A FILE
If the string to send starts with an at sign (@), the rest of the string is taken to be the name of a file to read to get the string to send. If the last character of the data read is a newline, it is removed. The file can be a named pipe (or fifo) instead of a regular file. This provides a way for chat to communicate with another program, for example, a program to prompt the user and receive a password typed in.

放弃字符串 ABORT STRINGS
许多数据机会以字串来回报呼叫的状况。 这些字串可能是 CONNECTED 或是 NO CARRIER 或是 BUSY 。 通常要是数据机连线到远端失败的话 应该会希望结束指令稿。 困难是指令稿不会确实地知道它可能接收到 哪个数据机字串。在某次尝试时， 他可能接收到 BUSY 然而下次它可 能接收到 NO CARRIER 。

这些〞失败〞字串可以用 ABORT 程序指定到指令稿中。像是下面这个 例子般地写到指令稿里：

    ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT

这个程序将不会期待什么；而且接著送出 ATZ 这个字串。对此期待的 回应是 OK 这个字串。当它接收到 OK 时，字串 ADTD5551212 就进行 拨号。期待字串是 CONNECT 。 如果字串 CONNECT 被接收到那么就会 执行指令稿其余的部份。然而，要是数据机发现电话忙线， 他将会送 出 BUSY 这个字串。 这会使得该字串符合失败字元程序(abort char- acter)。 这个指令稿将会因为它发现一个失败字串(abort string)而 失败(fail)。如果他接收到的是 NO CARRIER 字串， 它也会因为同样 的原因而失败。不是可以接收到字串就是字串将终结 chat 指令稿。

CLR_ABORT STRINGS
This sequence allows for clearing previously set ABORT strings. ABORT strings are kept in an array of a pre-determined size (at compilation time); CLR_ABORT will reclaim the space for cleared entries so that new strings can use that space.

SAY STRINGS
The SAY directive allows the script to send strings to the user at the terminal via standard error. If chat is being run by pppd, and pppd is running as a daemon (detached from its controlling terminal), standard error will normally be redirected to the file /etc/ppp/connect-errors.

SAY strings must be enclosed in single or double quotes. If carriage return and line feed are needed in the string to be output, you must explicitely add them to your string.

The SAY strings could be used to give progress messages in sections of the script where you want to have 'ECHO OFF' but still let the user know what is happening. An example is:

    ABORT BUSY
    ECHO OFF
    SAY "Dialling your ISP...\n"
    '' ATDT5551212
    TIMEOUT 120
    SAY "Waiting up to 2 minutes for connection ... "
    CONNECT ''
    SAY "Connected, now logging in ...
    ogin: account
    ssword: pass
    $ SAY "Logged in OK ... etc ...

This sequence will only present the SAY strings to the user and all the details of the script will remain hidden. For example, if the above script works, the user will see:

    Dialling your ISP...
    Waiting up to 2 minutes for connection ... Connected, now logging in ...
    Logged in OK ...

REPORT STRINGS
A report string is similar to the ABORT string. The difference is that the strings, and all characters to the next control character such as a carriage return, are written to the report file.

The report strings may be used to isolate the transmission rate of the modem's connect string and return the value to the chat user. The analysis of the report string logic occurs in conjunction with the other string processing such as looking for the expect string. The use of the same string for a report and abort sequence is probably not very useful, however, it is possible.

The report strings to no change the completion code of the program.

These "report" strings may be specified in the script using the REPORT sequence. It is written in the script as in the following example:

    REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account

This sequence will expect nothing; and then send the string ATDT5551212 to dial the telephone. The expected string is CONNECT. If the string CONNECT is received the remainder of the script is executed. In addition the program will write to the expect-file the string "CONNECT" plus any characters which follow it such as the connection rate.

CLR_REPORT STRINGS
This sequence allows for clearing previously set REPORT strings. REPORT strings are kept in an array of a pre-determined size (at compilation time); CLR_REPORT will reclaim the space for cleared entries so that new strings can use that space.

ECHO
The echo options controls whether the output from the modem is echoed to stderr. This option may be set with the -e option, but it can also be controlled by the ECHO keyword. The "expect-send" pair ECHO ON enables echoing, and ECHO OFF disables it. With this keyword you can select which parts of the conversation should be visible. For instance, with the following script:

    ABORT 'BUSY'
    ABORT 'NO CARRIER'
     ''
    ATZ
    OK\r\n ATD1234567
    \r\n \c
    ECHO ON
    CONNECT \c
    ogin: account

all output resulting from modem configuration and dialing is not visible, but starting with the CONNECT (or BUSY) message, everything will be echoed.

HANGUP
The HANGUP options control whether a modem hangup should be considered as an error or not. This option is useful in scripts for dialling systems which will hang up and call your system back. The HANGUP options can be ON or OFF.
When HANGUP is set OFF and the modem hangs up (e.g., after the first stage of logging in to a callback system), chat will continue running the script (e.g., waiting for the incoming call and second stage login prompt). As soon as the incoming call is connected, you should use the HANGUP ON directive to reinstall normal hang up signal behavior. Here is an (simple) example script:

    ABORT 'BUSY'
    '' ATZ
    OK\r\n ATD1234567
    \r\n \c
    CONNECT \c
    'Callback login:' call_back_ID
    HANGUP OFF
    ABORT "Bad Login"
    'Callback Password:' Call_back_password
    TIMEOUT 120
    CONNECT \c
    HANGUP ON
    ABORT "NO CARRIER"
    ogin:--BREAK--ogin: real_account
    etc ...

超时 TIMEOUT
初始的逾时值是 45 秒。这可以用 -t 参数来加以改变。

要对下一个期待字串改变逾时值的话，可以使用下面这个例子：

    ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2

这将会在期待 "login:" 提示的时候把逾时限制改成 10 秒。 逾时限 制接著在它寻找密码提示时被改成 5 秒。

逾时限制一旦改变就会持续作用直到它再度被改变。

SENDING 发送 EOT
EOT 这个特别的回复字串指示 chat 程式应该送出一个 EOT 字元到远 端去。这是一般的档案结束(End-of-file)字元程序。 在 EOT 后面并 不会跟著送出一个返回字元(return)。

这个 EOT 程序可以用 ^D 序列嵌入到送出的字串里。

产生中断 GENERATING BREAK
BREAK 这个特别的回复字串将会使得一个中断情况被送出。 这个中断 是传送端的一个特殊。接收端一般对此的处理是改变传输率。 它可以 用来循环测试远端可能的传输率直到你能够接到有效的签入提示。

这个中断程序可以用 \K 序列嵌入到送出的字串里。

转义序列 ESCAPE SEQUENCES
期待以及回复字串可以包含转义序列。 所有这种程序在回复字串中都 是合法的。有许多在期待字串中是合法的。 那些在期待程序中无效的 会被指出。

''  期待或送出一个空字串(null string) 。如果你送出一个空字 串那么它还会送出一个返回字元。这个程序可以是一对省略符 号(apostrophe)或者也可以是引用字元。

\\b 代表一个退位(backspace)字元。

\\c 抑制在回复字串结尾的新列(newline)字元。 这是送出没有返 回字元尾随的字串的唯一方法。它必须在送出字串的结尾。例 如，这个程序 hello

\\d 延迟一秒钟。该程式使用最长延迟为一秒的 sleep(1) 。（在 期待字串中无效。）

\\K 插入一个中断（在期待字串中无效。）

\\n 送出一个新列(newline)或换行(linefeed)字元。

\\N 送出一个空字元(null character)。同样的程序可以用 代 替。（在期待字串中无效。）

\\p 暂停一小段时间。延迟 1/10 秒。（在期待字串中无效。）

\\q 抑制字串写往 SYSLOG 档案。该 ?????? 字串被记录到自己的 空间。（在期待字串中无效。）

\\r 传送或期待一个机架返回（字元）

\\s 代替字串中的空白。这个可以用在不愿引用包含空白的字串之时。'HI TIM' 以及 HI\sTIM 是相同的。

\\t 传送或期待一个定位(tab)字元。

\\T Send the phone number string as specified with the -T option (not valid in expect.)

\\U Send the phone number 2 string as specified with the -U option (not valid in expect.)

\\\\
    传送或期待一个倒斜线(backslash)字元。

\\ddd
    将八进位数字 (ddd) 折叠(collapse)成单一的 ASCII 字元并 将其送出。（某些字元在期待字串中无效。）

^C  替换含有以 C 代表之控制字元的程序。例如，字元 DC1(17) 是以 ^Q 表示。（某些字元在期待字串中无效。）

ENVIRONMENT VARIABLES
Environment variables are available within chat scripts, if the -E option was specified in the command line. The metacharacter $ is used to introduce the name of the environment variable to substitute. If the substition fails, because the requested environment variable is not set, nothing is replaced for the variable.

TERMINATION CODES
The chat program will terminate with the following completion codes.

0   The normal termination of the program. This indicates that the script was executed without error to the normal conclusion.

1   One or more of the parameters are invalid or an expect string was too large for the internal buffers. This indicates that the program as not properly executed.

2   An error occurred during the execution of the program. This may be due to a read or write operation failing for some reason or chat receiving a signal such as SIGINT.

3   A timeout event occurred when there was an expect string without having a "-subsend" string. This may mean that you did not program the script correctly for the condition or that some unexpected event has occurred and the expected string could not be found.

4   The first string marked as an ABORT condition occurred.

5   The second string marked as an ABORT condition occurred.

6   The third string marked as an ABORT condition occurred.

7   The fourth string marked as an ABORT condition occurred.

... The other termination codes are also strings marked as an ABORT condition.

Using the termination code, it is possible to determine which event terminated the script. It is possible to decide if the string "BUSY" was received from the modem as opposed to "NO DIAL TONE". While the first event may be retried, the second will probably have little chance of succeeding during a retry.

参见 SEE ALSO
关于 chat 指令稿的其它资讯可以在 UUCP 文件里找到。chat 指令稿 的概念由 uucico 程式所使用的指令稿来的。

uucico(1), uucp(1)

COPYRIGHT
The chat program is in public domain. This is not the GNU public license. If it breaks then you get to keep both pieces.

[中文版维护人]
asdchen <asdchen@pc2.hinet.net>

[中文版最新更新]
1995/09/30

《中国linux论坛man手册翻译计划》:
http://cmpp.linuxforum.net

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