Question

我写了一个expect脚本，它有助于在远程机器上执行命令。执行完成后，我想获得一行用户输入，然后将其发送到远程bash，这是代码片段：

#! /usr/bin/env expect
...
spawn ssh -l $user $host
...
send_tty -- "Enter your command: " 
set timeout -1

# match only printable characters (prevent from pressing TAB)
expect_tty eof exit -re {([[:print:]]*)\n}
send_tty -- "\n"
set timeout 10

# send the command to remote shell
send "$expect_out(1,string)" 
expect "$GENERAL_PROMPT"

但是，如果输入类似于：ls /"，我的程序将被阻止，因为远程shell希望通过提示字符串“＆gt;”获得更多字符。实际上，我希望bash不会提示输入更多信息，而不仅仅是打印错误信息：

$ read COMMAND
ls /"
$ eval "$COMMAND"
bash: unexpected EOF while looking for matching `"'
bash: syntax error: unexpected end of file

我可以在我的剧本中实现这一目标吗？

Answer 1

#!/usr/bin/expect
set prompt "#|%|>|\\\$ $"; # A generalized prompt to match known prompts.
spawn ssh -l dinesh xxx.xx.xx.xxx
expect {
    "(yes/no)" { send "yes\r";exp_continue}
    "password" 
}
send "mypassword\r"
expect -re $prompt
send_tty -- "Enter your command: " 
set timeout -1

# match only printable characters (prevent from pressing TAB)
expect_tty eof exit -re {([[:print:]]*)\n}
send_tty -- "\n"
set timeout 10
puts "\nUSER INPUT : $expect_out(1,string)"

# send the command to remote shell 
# Using 'here-doc', to handle possible user inputs, instead of quoting it with any other symbol like single quotes or backticks
send "read COMMAND <<END\r"
expect -re $prompt
send "$expect_out(1,string)\r" 
expect -re $prompt
send "END\r"
expect -re $prompt

# Since we want to send the literal dollar sign, I am sending it within braces
send {eval $COMMAND}
# Now sending 'Return' key
send "\r"
expect -re $prompt

为什么＆＃39; here-doc＆＃39;用过？

如果我使用反引号或单引号来转义命令，那么如果用户在命令本身中给出了反引号或单引号，那么它可能会失败。所以，为了克服这个问题，我已经添加了here-doc。

输出

dinesh@MyPC:~/stackoverflow$ ./zhujs
spawn ssh -l dinesh xxx.xx.xx.xxx
dinesh@xxx.xx.xx.xxx's password: 

[dinesh@lab ~]$ matched_literal_dollar_sign
Enter your command: ls /"


USER INPUT : ls /"
read COMMAND <<END
> ls /"
> END
[dinesh@lab ~]$ eval $COMMAND
-bash: unexpected EOF while looking for matching `"'
-bash: syntax error: unexpected end of file
[dinesh@lab ~]$ dinesh@MyPC:~/stackoverflow$

更新：

使用here-doc的主要原因是它使读取作为非阻塞命令。即我们可以快速完成下一个命令。否则，我们必须等到Expect的超时。（当然，我们可以动态更改超时值。）

这只是一种做法。只要拥有read命令，您就可以根据需要更改它。

Answer 2

我认为这对interact来说是一个很好的例子 - 期望放弃并让用户直接与衍生程序进行交互。

spawn ssh -l $user $host
#...

send_user "You are now about to take control: type QQQ to return control to the program\n"

interact {
    QQQ   return
}

send_user "Thanks, I'm back in charge ...\n"

Answer 3

这是一个单行版本

read > export cmd ; eval $cmd ; unset cmd

获取一行用户输入，然后将其作为Bash命令执行

3 个答案: