bash envsubst 有转义字符吗？
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is there an escape character for envsubst?
提问by quinn
Is there a way to prevent envsubstfrom substituting a $VARIABLE? For example, I would expect something like:
有没有办法防止envsubst替换 a $VARIABLE？例如，我希望是这样的：
export THIS=THAT
echo "dont substitute \$THIS" | envsubst
and have it return
并让它返回
dont substitute $THIS
but instead I get
但我得到
dont substitute \THAT
is there any escape character for doing this?
这样做有什么转义字符吗？
采纳答案by iokanuon
export DOLLAR='$'
export THIS=THAT
echo '${DOLLAR}THIS' | envsubst
Or more clear:
或者更清楚：
export THIS=THAT
echo '${DOLLAR}THIS' | DOLLAR='$' envsubst
回答by chepner
If you give envsubsta list of variables, it onlysubstitutes those variables, ignoring other substitutions. I'm not exactly sure how it works, but something like the following seems to do what you want:
如果您提供envsubst变量列表，它只会替换这些变量，而忽略其他替换。我不确定它是如何工作的，但类似以下的内容似乎可以满足您的需求：
$ export THIS=THAT FOO=BAR
$ echo 'dont substitute $THIS but do substitute $FOO' | envsubst '$FOO'
dont substitute $THIS but do substitute BAR
Note that $THISis left alone, but $FOOis replaced by BAR.
请注意，$THIS保持不变，但$FOO被替换为BAR。
回答by blueFast
My workaround is as follows:
我的解决方法如下：
Original template:
原始模板：
$change_this
$dont_change_this
Editted template:
编辑模板：
$change_this
§dont_change_this
Now you can process:
现在您可以处理：
envsubst < $template | sed -e 's/§/$/g'
This relies on the character §not occurring anywhere else on your template. You can use any other character.
这依赖于§没有出现在模板上其他任何地方的字符。您可以使用任何其他字符。
回答by user2658308
In my case I wanted to only escape vars that aren't already defined. To do so run:
就我而言，我只想转义尚未定义的变量。为此，请运行：
envsubst "$(env | sed -e 's/=.*//' -e 's/^/\$/g')"
envsubst "$(env | sed -e 's/=.*//' -e 's/^/\$/g')"
回答by Malvineous
If there's only one or two variables you don't want to expand, you can sort of whitelist them by temporarily setting them to their own name, like this:
如果只有一两个变量您不想扩展，您可以通过将它们临时设置为自己的名称来将它们列入白名单，如下所示：
$ echo 'one $two three $four' | four='$four' envsubst
one three $four
Here, the $fourvariable gets replaced with $four, effectively leaving it unchanged.
在这里，$four变量被替换为$four，有效地保持不变。
回答by Lech Paw?aszek
$?echo $SHELL
/bin/bash
$ echo $SHELL
$SHELL
$ echo $SHELL | envsubst
/bin/bash
$ echo $${q}SHELL | envsubst
$SHELL
So doing $$allows you to add a $character. Then just "substitute" non-existent variable (here I used ${q}but can be something more meaningful like ${my_empty_variable}and you'll end up with what you need.
这样做$$可以让您添加一个$字符。然后只是“替换”不存在的变量（这里我使用了${q}但可以更有意义的东西${my_empty_variable}，你最终会得到你需要的。
Just as with the paragraph solution - you need something special - here... a non-existent variable, which I like a bit more than performing additional sed on templates.
就像段落解决方案一样——你需要一些特别的东西——这里......一个不存在的变量，我更喜欢它而不是在模板上执行额外的 sed。
回答by admin
If you use envsubstfor Docker or you don't like his behavior, you can try my solution for replacing env variables in files: https://github.com/roquie/smalte
如果你使用envsubstDocker 或者你不喜欢他的行为，你可以尝试我的解决方案来替换文件中的 env 变量：https: //github.com/roquie/smalte
