强制bash的扩大变量从文件加载一个字符串 [英] Forcing bash to expand variables in a string loaded from a file

问题描述

我试图找出如何让bash的（强制？）在一个字符串变量扩展（这是从文件加载）。

I am trying to work out how to make bash (force?) expand variables in a string (which was loaded from a file).

我有一个名为something.txt的内容的文件：

I have a file called "something.txt" with the contents:

hello $FOO world

我然后运行

export FOO=42
echo $(cat something.txt)

这将返回：

   hello $FOO world

它并没有扩大，即使变量设置$ FOO。我不能EVAL或源文件 - 因为它会尝试并执行它（它不是可执行的，因为它是 - 我只是想插入变量的字符串）。

It didn't expand $FOO even though the variable was set. I can't eval or source the file - as it will try and execute it (it isn't executable as it is - I just want the string with the variables interpolated).

任何想法？

推荐答案

我无意中发现了什么，我觉得是这个问题的答案：在 envsubst 命令

I stumbled on what I think is THE answer to this question: the envsubst command.

envsubst < something.txt

在情况下，它是不是已经在你的发行版可用，它在
GNU包的gettext 。

In case it's not already available in your distro, it's in the GNU package gettext.

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