$的含义?(美元问号)在 shell 脚本中 [英] Meaning of $? (dollar question mark) in shell scripts

问题描述

做什么

echo $?

shell 编程中的意思?

解决方案

这是上次执行命令的退出状态.

例如命令 true 总是返回状态 0 而 false 总是返回状态 1:

真回声 $?# 回显 0错误的回声 $?# 回声 1

来自手册:(可通过在 shell 中调用 man bash 访问)

<块引用>

$? 扩展到最近执行的前台管道的退出状态.

按照惯例，退出状态 0 表示成功，非零返回状态表示失败.详细了解退出状态维基百科.>

还有其他类似的特殊变量，您可以在本在线手册中看到:https://www.gnu.org/s/bash/manual/bash.html#Special-Parameters

What does

echo $?

mean in shell programming?

解决方案

This is the exit status of the last executed command.

For example the command true always returns a status of 0 and false always returns a status of 1:

true
echo $? # echoes 0
false
echo $? # echoes 1

From the manual: (acessible by calling man bash in your shell)

$?       Expands to the exit status of the most recently executed foreground pipeline.

By convention an exit status of 0 means success, and non-zero return status means failure. Learn more about exit statuses on wikipedia.

There are other special variables like this, as you can see on this online manual: https://www.gnu.org/s/bash/manual/bash.html#Special-Parameters

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