带有2& 1和命令提示符的意外重定向结果 [英] Unexpected redirect result with 2>&1 and command prompt

问题描述

我在玩nc，因为-e命令消失了，所以推荐

I was playing around with nc and since the -e command is gone, it recommended

cat /tmp/f | /bin/sh -i 2>&1 | nc -l 127.0.0.1 1234 > /tmp/f

我认为"2>& 1"是不必要的，因为我不需要知道我将要运行的简单命令(例如"whoami"，"ls"等)的错误，因此我的命令改为是

I thought that the "2>&1" is unnecessary because I don't need to know the errors of the simple commands I was going to run like "whoami", "ls", etc. so my command instead is

cat /tmp/f | /bin/sh -i | nc -l 127.0.0.1 1234 > /tmp/f

但是，然后，我没有得到干净"的结果.这就是我得到的

But then, I don't get "clean" results. This is what I get

服务器:

Listening on [0.0.0.0] (family 0, port 1234)
$  $

客户:

nc localhost 1234
ls 
testfile
whoami
user1

基本上，我在客户终端中看不到$.当我对2>& 1执行命令时，我得到了期望的结果

Basically, I don't see the $ in my client terminal. When I do the command with the 2>&1, I get what I expected

服务器:

Listening on [0.0.0.0] (family 0, port 1234)

客户:

nc localhost 1234
$ ls 
testfile
$ whoami
user1

我知道2>& 1表示将stderr重定向到stdout，因此在这种情况下，命令提示符"$"在stderr中如何?它不应该是stdin的一部分吗?

I know that 2>&1 means redirect stderr to stdout so in this case, how is the command prompt "$" part of the stderr? Shouldn't it be part of stdin?

推荐答案

shell使用标准错误流来显示提示，以及使用 select 和其他任何文本创建的菜单是为了与用户互动.

The shell uses the standard error stream for prompts, and also for menus created by select, and any other text that is meant for interacting with the user.

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