RegExp: is there way to pass string to regexp without ecranisation?

Question

Is there way to pass some string to regexp and not worry about ecranisation of special chars.

For example I wont to find line which starts with words "\north+west\", as you can see "\n" and "h+" should be ecranised. So question is there some special combination to write text as it is?

/^\s+(<some special combination> \north+west\)\s+/i

or maybe you know function which can properly ecranise my text?

Most languages provide some function to escape strings that should be inserted into a regular expression. Which language do you use? — Till Helge, Apr 12 '13 at 13:02
Please note that the description for the `regex` tag states: *Please also include a tag specifying the programming language or tool you are using.* — Jon Clements, Apr 12 '13 at 13:04
@TillHelgeHelwig right now I need it in PHP but I thought there can be standard way for all PCRE languages — redexp, Apr 12 '13 at 15:06

score 1 · Accepted Answer · answered Apr 12 '13 at 15:13

1

In PHP and Perl you can use \Q...\E delimiters to autoescape metacharacters inside regexp. Quoting the doc:

\Q and \E can be used to ignore regexp metacharacters in the pattern. For example: \w+\Q.$.\E$ will match one or more word characters, followed by literals .$. and anchored at the end of the string.

answered Apr 12 '13 at 15:13

raina77ow

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just found [\Q...\E doesn't work in JavaScript](http://stackoverflow.com/a/5664273/815295) "Hulk sad" :( – redexp Apr 12 '13 at 15:20
Yep, it doesn't work in JS; that's why you were asked to provide a language tag as well, btw. ) But there's a plenty of 'autoescaping' code out there; in fact, jQuery UI (and other popular tools) have the corresponding methods in their libraries. – raina77ow Apr 12 '13 at 15:22

score 0 · Answer 2 · edited May 23 '17 at 11:53

In addition to @raina77ow answer, when you use pcre via a language like PHP that needs pattern delimiters, you can't use the \Q...\E feature if your string contains the opening or the closing delimiter. For example, you can't write patterns like:

/\Qabc/def\E/
~\Qabc~def\E~
[\Qabc[def\E]
[\Qabc]def\E]
(\Qabc)def\E)
(\Qabc(def\E)

The only way is to use the preg_quote function and to put the delimiter (only if this one isn't already a special regex character) in its second parameter.

RegExp: is there way to pass string to regexp without ecranisation?

2 Answers2