如何在变量中存储标准错误 [英] How to store standard error in a variable

问题描述

假设我有一个如下脚本:

Let's say I have a script like the following:

useless.sh

useless.sh

echo "This Is Error" 1>&2
echo "This Is Output" 

我还有另一个shell脚本:

And I have another shell script:

alsoUseless.sh

alsoUseless.sh

./useless.sh | sed 's/Output/Useless/'

我想从useless.sh中捕获"This Is Error"或任何其他stderr到一个变量中. 我们称它为错误.

I want to capture "This Is Error", or any other stderr from useless.sh, into a variable. Let's call it ERROR.

请注意，我正在使用stdout进行操作.我想继续使用stdout，因此在这种情况下，将stderr重定向到stdout并没有帮助.

Notice that I am using stdout for something. I want to continue using stdout, so redirecting stderr into stdout is not helpful, in this case.

所以，基本上，我想做

./useless.sh 2> $ERROR | ...

但这显然行不通.

我也知道我可以做

./useless.sh 2> /tmp/Error
ERROR=`cat /tmp/Error`

但这很丑陋和不必要.

不幸的是，如果没有答案，这就是我要做的.

Unfortunately, if no answers turn up here that's what I'm going to have to do.

我希望还有另一种方式.

I'm hoping there's another way.

有人有更好的主意吗?

推荐答案

这样捕获错误文件会更整洁:

It would be neater to capture the error file thus:

ERROR=$(</tmp/Error)

shell可以识别出这一点，而不必运行'cat'来获取数据.

The shell recognizes this and doesn't have to run 'cat' to get the data.

更大的问题很难解决.我认为没有简单的方法可以做到这一点.您必须将整个管道构建到子外壳中，最终将其最终标准输出发送到文件中，以便可以将错误重定向到标准输出.

The bigger question is hard. I don't think there's an easy way to do it. You'd have to build the entire pipeline into the sub-shell, eventually sending its final standard output to a file, so that you can redirect the errors to standard output.

ERROR=$( { ./useless.sh | sed s/Output/Useless/ > outfile; } 2>&1 )

请注意，需要使用分号(当然，在经典的shell中-Bourne，Korn-也可能在Bash中). '{}'通过附带的命令进行I/O重定向.如所写，它也会捕获来自sed的错误.

Note that the semi-colon is needed (in classic shells - Bourne, Korn - for sure; probably in Bash too). The '{}' does I/O redirection over the enclosed commands. As written, it would capture errors from sed too.

警告:未经测试的正式代码-使用风险自负.

WARNING: Formally untested code - use at own risk.

这篇关于如何在变量中存储标准错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！