bash 是否可以从子shell获取退出代码？
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Is it possible to get the exit code from a subshell?
提问by Geo
Let's imagine I have a bash script, where I call this:
假设我有一个 bash 脚本，我称之为：
bash -c "some_command"
do something with code of some_command here
Is it possible to obtain the code of some_command? I'm not executing some_commanddirectly in the shell running the script because I don't want to alter it's environment.
是否有可能获得的代码some_command？我没有some_command直接在运行脚本的 shell 中执行，因为我不想改变它的环境。
回答by Matti Virkkunen
$?will contain the return code of some_commandjust as usual.
$?将some_command像往常一样包含返回码。
Of course it might also contain a code from bash, in case something went wrong before your command could even be executed (wrong filename, whatnot).
当然，它也可能包含来自 bash 的代码，以防在您的命令甚至可以执行之前出现问题（错误的文件名，诸如此类）。
回答by Paused until further notice.
Here's an illustration of $?and the parenthesis subshell mentioned by Paggasand Matti:
这是Paggas和Matti$?提到的括号子外壳的说明：
$ (exit a); echo $?
-bash: exit: a: numeric argument required
255
$ (exit 33); echo $?
33
In the first case, the code is a Bash error and in the second case it's the exit code of exit.
在第一种情况下，代码是 Bash 错误，在第二种情况下，它是exit.
回答by Paggas
You can use the $?variable, check out the bash documentation for this, it stores the exit status of the last command.
您可以使用该$?变量，为此查看 bash 文档，它存储最后一个命令的退出状态。
Also, you might want to check out the bracket-style command blocks of bash (e.g. comm1 && (comm2 || comm3) && comm4), they are always executed in a subshell thus not altering the current environment, and are more powerful as well!
此外，您可能想查看 bash 的括号样式命令块（例如comm1 && (comm2 || comm3) && comm4），它们总是在子shell 中执行，因此不会改变当前环境，而且功能更强大！
EDIT: For instance, when using ()-style blocks as compared to bash -c 'command', you don't have to worry about escaping any argument strings with spaces, or any other special shell syntax. You directly use the shell syntax, it's a normal part of the rest of the code.
编辑：例如，与 bash -c 'command' 相比，使用 () 样式块时，您不必担心使用空格或任何其他特殊 shell 语法转义任何参数字符串。您直接使用 shell 语法，它是其余代码的正常部分。
