How to match "[" and "]" in regexp?

Question

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.

Answer 1

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"\[" (raw string) in Python
• R"(\])" or R"foo(\])foo" in C++11 (raw string literal). A raw string lives between parentheses, which can be surrounded by an optional delimiter (foo in the second version).

Reference

Interesting Character Classes

Answer 2

\[ and ] should work. In some languages you may have to double escape. (i.e. \\[ and ]).

Note: You don't need to escape ] :)

DEMO: http://regex101.com/r/vP4mQ9/1