为什么我无法在gawk中转义报价? [英] Why can't I escape quote in gawk?

问题描述

我正在尝试执行以下操作，但是要么我太累了，无法思考，要么逃生过程中出现了奇怪的事情:

I'm trying to do the following, but either I'm way too tired and can't think, or something weird is hapening with the escapes:

scanimage -L | gawk '/N650U/ {print gensub("[\'`]", "", "g", $2)}'
pipe bquote> 

推荐答案

惯用的做法是创建一个包含单引号的变量，然后使用该变量:

The idiom to do this is to create a variable which contains the single quote and then use that:

scanimage -L | gawk '/N650U/ {print gensub(q"`", "", "g", $2)}' q="'"

但是，由于您是在字符类中使用它的，因此无法正常工作，因此您需要执行以下操作:

However, since you are using it in a character class, that is not going to work so you'll need to do this:

scanimage -L | gawk '/N650U/ {print gensub("[`'\'']", "", "g", $2)}'
                    <--      1st pair       -->  <--   2nd pair  -->

如果使用bash的另一种选择是使用 支持转义单引号的$''

Another alternative if using bash is to use $'' which does support escaping single-quotes

scanimage -L | gawk $'/N650U/ {print gensub("[`\']", "", "g", $2)}'

在第二种情况下，您要做的就是在字面单引号之前创建一个单引号对，转义该单引号，以便外壳程序不解释它，然后在其后再创建另一个单引号对./p>

在正则表达式中使用单引号的示例

All you are doing in the 2nd case is creating a single-quote pair right before your literal single-quote, escaping the single quote so the shell doesn't interpret it and then make another single-quote pair after it.

$ echo $'foo`\'' | awk '{gsub(/[o`'\'']/,"#")}1'
f####

在正则表达式外使用单引号的示例

$ echo "foo" | awk '{print q$0q}' q="'"
'foo'

在$''

中包含单引号的示例

Example with single-quote inside $''

echo $'foo`\'' | awk $'{gsub(/[o`\']/,"#")}1'
f####

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