什么＆QUOT; $＆QUOT;给我们正好在shell脚本？ [英] What does "$?" give us exactly in a shell script?

问题描述

我看到了code写的某个地方，我想知道究竟是什么$？ DO /给我们。
谷歌搜索并没有帮助。

I saw the code written somewhere online, and I wanted to know what exactly does "$?" do/give us. Googling did not help.

这里的code我看到它：

Here's the code I saw it in:

#!/bin/sh

ping -c 2 localhost
if [ $? != 0 ] ; then
    echo "Couldn't ping localhost, weird"
    fi

ping -c 2 veryweirdhostname.noend 
if [ $? != 0 ] ; then
    echo "Surprise, Couldn't ping a very weird hostname.."
    fi

echo "The pid of this process is $$"

来自：<一href=\"http://efod.se/writings/linuxbook/html/shell-scripts.html\">http://efod.se/writings/linuxbook/html/shell-scripts.html

推荐答案

$？是一个变量抱着你运行的最后一个命令的返回值。

$? is a variable holding the return value of the last command you ran.

例C程序（ example.c ）

int main() { return 1; }

Bash实例：

Example Bash:

gcc -o example example.c
./example
echo $? # prints 1

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