获取管道后台进程的退出代码 [英] Get exit code of a piped background process

问题描述

someCommand 2>&1 | grep pattern &

如何获取someCommand的退出状态?

PIPESTATUS不起作用，因为它是一个后台进程.

PIPESTATUS doesn't work because it's a background process.

我发现了这个

I've found this link and it seems to work but only if I use it exactly that way. Simple echoing to the screen doesn't seem to work. I was wondering if it's possible to get the exit code without creating temporary files.

推荐答案

在bash中，您可以执行以下操作:

In bash you could do :

echo "${PIPESTATUS[0]} ${PIPESTATUS[1]}"

示例:

$ ls -l | grep somefile
-rw-rw-r--  1 me me     32 May  4 15:47 somefile
$ echo "${PIPESTATUS[0]} ${PIPESTATUS[1]}"
0 0

$ ls -l 1>/dev/null | grep while
$ echo "${PIPESTATUS[0]} ${PIPESTATUS[1]}"
0 1

用于管道前台进程

如果是脚本，请说包含以下内容的testscript.sh:

In case of a script say testscript.sh which contains :

#!/bin/bash
echo "Some Stuff"
exit 29 # Some random exit code for testing

做

$./testscript.sh | grep somestuff
$ echo "${PIPESTATUS[0]} ${PIPESTATUS[1]}"
29 1

用于管道后台进程

方法1:使用pipefail

Method 1: Using pipefail

对于包含以下内容的testscript.sh:

For testscript.sh which contains :

#!/bin/bash
set -eo pipefail  
#set -o pipefail causes a pipeline to produce a failure return code
#If a command fails, set -e will make the whole script exit,
cat nonexistingfile # this command fails
echo "Some Stuff"
exit 29

做

$ ./testscript.sh 2>/dev/null | grep Some &
[2] 7684
$ fg 2
bash: fg: job has terminated
[2]-  Exit 1         ./testscript.sh 2> /dev/null | grep --color=auto Some

您将获得退出状态1，从中您可以得出结论脚本失败.

You get an the exit status 1 from which you conclude that the script failed.

如果已删除cat nonexistingfile，您将获得:

Had cat nonexistingfile been removed you would have got:

[2]-  Done                    ./37257668.sh 2> /dev/null | grep --color=auto Some

缺点:pipefail将为所有退出代码返回一个非失败命令专用的退出代码

Disdvantage : pipefail will return a one for all exit code that is not specific to the command that failed

方法2:获取Shell脚本

$ . ./testscript.sh 2>/dev/null | grep Some & #mind the dot in the beginning
$ echo "${PIPESTATUS[0]} ${PIPESTATUS[1]}"
29 0

最终触摸

如果您怀疑单个命令在shell脚本(测试脚本)中失败，则可以执行以下操作:

If you suspect a single command to fail in a shell script,test script, you could do below :

#no shebang
echo "Some Stuff"
ls non_existent 2>/dev/null || ls__return_value=50 

做

$. ./testscript | grep "Some"

$if [ $ls__return_value -eq 50 ]; then echo "Error in ls"; fi

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