为什么要在复制/粘贴到终端之前先运行cat | bash? [英] Why would one run cat|bash before copying/pasting into a terminal?

问题描述

在将命令从剪贴板粘贴到终端之前，我见过有人在运行 cat | bash .

I've seen someone running cat|bash before pasting commands from the clipboard into a terminal.

bash 在bash中执行命令，我不知道为什么我们在这里需要 cat 和 |(pipe).

bash executes commands in bash I do not know why do we need cat here and |(pipe).

这种做法有什么有益的作用?

What useful effects does this practice have?

推荐答案

是我的同事在终端中执行了一堆命令，在粘贴这些命令集之前，他做了 cat | bash

他很可能会阻止Bash将命令中的任何内容解释为编辑输入，以覆盖他设置的所有特殊键绑定和别名，和/或防止命令将命令流用作输入.

He likely this to stop Bash from interpreting anything in the commands as editing input, to override any special keybindings and aliases he's set up, and/or to prevent commands from consuming the command stream as input.

将此命令与两个嵌入式制表符一起考虑:

Consider this command with two embedded tab characters:

    if true
    then
        echo "yup"
    fi

将其粘贴到外壳中时会发生以下情况(因为制表符会触发交互式输入中的制表符完成):

Here's what happens when you paste it into a shell (because the tab characters trigger tab completion in interactive input):

$ if true
> then
>
Display all 2600 possibilities? (y or n)
!                                   grub-mkfont                         pnmmontage
./                                  grub-mkimage                        pnmnlfilt
:                                   grub-mklayout                       pnmnoraw

这是涉及 ssh 的代码段:

ssh localhost uptime
echo "Finished"

将其粘贴到外壳中时，第二个命令将被 ssh 用作输入，因此您将获得以下信息:

When you paste it into a shell, the second command gets consumed as input by ssh, so you get this:

$ ssh localhost uptime
 09:53:40 up 28 days, 18:33, 25 users,  load average: 0.06, 0.01, 0.00

在两种情况下，都粘贴到 cat |bash 会导致命令按原样运行.

In both cases, pasting into cat | bash instead will cause the commands to run as-is.

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