如何捕获if块的变量中的命令错误消息 [英] how to capture command error message in variable for if block

问题描述

您好，以下是我的bash shell脚本代码，在此我想捕获if子句的错误消息，当它说作业已经在运行或无法将作业启动到变量时，在下面的脚本中怎么可能，或其他任何用于以下功能的方式

Hi below is my code for bash shell script, in this I want to capture error message for if clause, when it says either job is already running or unable to start the job to a variable, how it is possible in below script, or any other way for the below functionality

if initctl start $i  ; then
    echo "service $i  started by script"
else
    echo "not able to start service $i"
fi

推荐答案

例如，您可以使用语法 msg = $(command 2>& 1 1>/dev/null)重定向将stdout重定向到/dev/null后，将stderr转换为stdout.这样，它将只存储stderr:

You can for example use the syntax msg=$(command 2>&1 1>/dev/null) to redirect stderr to stdout after redirecting stdout to /dev/null. This way, it will just store stderr:

error=$(initctl start $i 2>&1 1>/dev/null)
if [ $? -eq 0 ]; then
   echo "service $i started by script"
else
   echo "service $i could not be started. Error: $error"
fi

这使用如何用管道输送stderr而不是stdout?，以便从 initctl start $ i 捕获stderr并将其存储在 $ error 变量中.

This uses How to pipe stderr, and not stdout?, so that it catches stderr from initctl start $i and stores in $error variable.

然后， $?包含命令的返回码，如

Then, $? contains the return code of the command, as seen in How to check if a command succeeded?. If 0, it succeeded; otherwise, some errors happened.

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