如何在Expect脚本中清理先前的Expect_buf [英] how to clean up the previous expect_buf in an expect script

问题描述

我已经编写了一个Expect函数来获取命令的输出，而我的代码如下所示

I've written a expect function to get the output of a command and my code is like below

proc do_cmd {cmd id} {
  set spawn_id $id
  send "$cmd\r"
  expect "$cmd\r"
  expect {
    -re "\n(.*)\r\n" {return $expect_out(1,string)}
    default {exit 1}
  }
}

如果我只调用一次函数就可以正常工作并返回我想要的东西，但是如果我不间断地连续调用它，它将返回不需要的东西.

If I call the function just once it would works fine and return something I want, but if I call it continually without a break, it would return something unwanted.

# test case 1
set ret [do_cmd $mycmd $spawn_id]
puts "$mycmd returns $ret"  # the return value is ok

# test case 2
set ret [do_cmd $mycmd $spawn_id]
set ret [do_cmd $mycmd $spawn_id]
puts "$mycmd returns $ret"  # the return value is not something I want

我使用'exp_internal 1'对其进行调试，发现第二个被调用命令中的Expect_out仍然保留了先前的输出信息并引起了匹配的问题，因此，我该如何清理Expect_out缓冲区(我试图对其进行设置一个空字符串，但它不起作用，)还是我可以做些其他事情来避免此问题?预先感谢.

I use the 'exp_internal 1' to debug it and found that the expect_out in the second called command still holds the previous output info and caused the matched problem, so how can I clean up the expect_out buffer(I tried to set it an empty string but it doesn't work,) or is there anything else I can do to avoid this problem? Thanks in advance.

推荐答案

Don Libes对您的方案的建议如下，

Don Libes's suggestion for your scenario is as follows,

有时甚至说:

Sometimes it is even useful to say:

expect *

此处*匹配任何内容.这就像在说:我不在乎 在输入缓冲区中.扔掉."这种模式始终匹配，甚至 如果那里什么都没有.请记住，*匹配任何东西，而空 字符串是什么！作为此行为的必然结果，此命令 总是立即返回.它从不等待新数据到达.它 不需要，因为它可以匹配所有内容.

Here the * matches anything. This is like saying, "I don't care what's in the input buffer. Throw it away." This pattern always matches, even if nothing is there. Remember that * matches anything, and the empty string is anything! As a corollary of this behavior, this command always returns immediately. It never waits for new data to arrive. It does not have to since it matches everything.

参考资料:探索期望

在这种情况下，在您需要进行匹配之后，最好尝试将匹配保存到某个变量中，然后在最后简单地添加代码expect *.这将清空缓冲区.您的代码可以进行如下更改.

In this case, after your required match, better try to save the match to some variable then simply add the code expect * at the last. This will empty the buffer. Your code can altered as below.

proc do_cmd {cmd id} {
  set spawn_id $id
  send "$cmd\r"
  #Looks like you are looking for a particular command to arrive
  expect "$cmd\r"
  #Then you have one more expect here which is you want to get it
  expect {
    #Saving the value sub match to the variable 'result'
    -re "\n(.*)\r\n" {set result $expect_out(1,string)}}
    }
  #Causing the buffer to clear and it will return quickly
  expect *
  return $result
}

除此之外，还有另一种方法可以取消设置expect_out(buffer)内容本身，这将从expect_out数组中删除缓冲区"索引，该索引可以表示为

Apart from this, there is one more way can be unsetting the expect_out(buffer) content itself which will remove the 'buffer' index from expect_out array which can be depicted as

unset expect_out(buffer)

当下一次匹配发生时，expect_out数组将被更新为索引"buffer"，我们可以得到新的expect_out(buffer)值.如果您更喜欢用这种方式，请用上面的代码替换expect *.

When the next match happens, expect_out array will be updated the index 'buffer' and we can have the fresh expect_out(buffer) value. Replace the expect * with the above code if you prefer to use this way.

这是一种变通办法，可以实际获得我们想要的东西.您可以采用任何方法.选择是你的. :)

This is quite a workaround kind of stuff to get what we want actually. You can go ahead with any approach. Choice is yours. :)

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