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

问题描述

假设我有一个如下所示的脚本:

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

无用的.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/'

我想将这是错误"或 useless.sh 中的任何其他 stderr 捕获到一个变量中.我们称之为错误.

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，我将标准输出用于某些目的.我想继续使用 stdout，因此在这种情况下，将 stderr 重定向到 stdout 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.

我也知道我可以做到

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

但这既丑陋又不必要.

不幸的是，如果这里没有答案，那就是我将要做的.

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

我希望有另一种方式.

有人有更好的想法吗?

推荐答案

这样捕获错误文件会更简洁:

It would be neater to capture the error file thus:

ERROR=$(</tmp/Error)

shell 识别出这一点并且不必运行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.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 shell 中，最终将其最终标准输出发送到文件中，以便您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，分号是必需的(在经典 shell 中 - Bourne、Korn - 当然；可能在 Bash 中也是如此).'{}' 通过包含的命令执行 I/O 重定向.正如所写，它也会从 sed 中捕获错误.

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:未经正式测试的代码 - 使用风险自负.

WARNING: Formally untested code - use at own risk.

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