How to match "[" and "]" in regular expression?
This one does not work: [\\[\\]]
I thought that \\ enables use of special character. I want to match them inside a class.
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Over Killer
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I'm using C++11 regular expressions inside string. – Over Killer Jul 25 '14 at 12:37
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2Note that you don't need to escape everything twice if you use a raw string literal: `R"([\[\]])"` – chris Jul 25 '14 at 13:08
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It depends on your engine, and on whether you want to match a specific bracket (opening vs. closing), or to match a class of brackets.
\[matches opening bracket\]matches closing bracket[][]matches one char that is either an opening or closing bracket (.NET, Perl, PCRE, Python)[]\[]same as above (Java and the 4 engines above)[[\]]same as above (JavaScript and the 4 engines above)[\]\[]same as above (Ruby, all engines)
Avoiding Backslash Soup
A handful of languages, such as Java, requires you to escape backslashes in the regex string, leading to \\[ and other unsightly variations. Fortunately, most languages give you ways to avoid escaping backslashes.
"\["can be used as is in JavaScript, PHP, Perl, Ruby, VB.NET, VBScript@"\["(verbatim string) in C#r"\["(raw string) in PythonR"(\])"orR"foo(\])foo"in C++11 (raw string literal). A raw string lives between parentheses, which can be surrounded by an optional delimiter (fooin the second version).
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zx81
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If i use ```\[``` or ```\]```, i'm getting warning about unregonized escape literal. – Over Killer Jul 25 '14 at 12:39
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@user3811473 It does in some engines, Ruby for instance. This is why I gave all these examples about the different engines. – zx81 Jul 25 '14 at 12:52
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@zx81: agreed, I'll leave my answer for extra info but voted up your answer because its more complete :) – user3811473 Jul 25 '14 at 12:57
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@GermánDiago Saw your edit attemps. Good idea to explain string options. Added a section for this, and took the C++11 from your suggestions after minor edits—thank you. :) – zx81 Jul 25 '14 at 20:27
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\[ and ] should work.
In some languages you may have to double escape. (i.e. \\[ and ]).
Note: You don't need to escape ] :)
user3811473
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Now I'm getting this error: ```regex_error(error_brack): The expression contained mismached [ and ]```. Regexp: ```\\[]``` (it is inside of string) – Over Killer Jul 25 '14 at 12:47
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Not really a concrete text. I want know that a form won't contain any "non-name" chars. – Over Killer Jul 25 '14 at 12:55