ack-grep:字符转义 [英] ack-grep: chars escaping

问题描述

我的目标是找到所有带有 ack 的<?=".我该怎么做?

My goal is to find all "<?=" occurrences with ack. How can I do that?

ack "<?="

不起作用.请告诉我如何解决这里的转义问题?

Doesn't work. Please tell me how can I fix escaping here?

推荐答案

由于 ack 使用 Perl 正则表达式，所以你的问题源于 Perl RegEx 语言中，? 是一个特殊字符，意思是最后一次匹配是可选的".所以你要搜索的是 = 前面是一个可选的 <

Since ack uses Perl regular expressions, your problem stems from the fact that in Perl RegEx language, ? is a special character meaning "last match is optional". So what you are grepping for is = preceded by an optional <

所以你需要转义 ? 如果它只是一个普通字符.

So you need to escape the ? if that's just meant to be a regular character.

要转义，有两种方法 - <?= 或 <[?]=;有些人发现第二种转义形式(将特殊字符放入字符类)比反斜杠转义更易读.

To escape, there are two approaches - either <?= or <[?]=; some people find the second form of escaping (putting a special character into a character class) more readable than backslash-escape.

UPDATE 正如 Josh Kelley 在评论中慷慨地添加的那样，第三种转义形式是使用 Q 运算符，该运算符将以下所有特殊字符转义，直到 遇到E，如下:Q

UPDATE As Josh Kelley graciously added in the comment, a third form of escaping is to use the Q operator which escapes all the following special characters till E is encountered, as follows: Q<?=E

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