Match One of Many Characters

Character class

Create a character class to match one occurrence inside a []

c[ae]l[ae]nd[ae]r

Range operator

Create a certain range using -

Match one of hexadecimal characters:

[a-fA-F0-9]

Reversed range like [f-a] are not valid

Negation operator

Negate a range using leading ^

Match Non-hexadecimal characters:

[^a-fA-F0-9]

Escape inside character class

There's four special characters may need to be escaped:

• - range operator
• ^ negation operator
• [ and ] start and end of character class

For any character that are not one of above, is not required to be escaped:

[$()*+.?{|]

For ^s not act as negation are not required to be escaped:

[a-f^A-F\^0-9]

Also for - and [/]

INFO

It's recommended to always escape metacharacters in character classes

Shorthand character classes

• \d matches any single digit, equivalent to [\d] and [0-9]
• \D matches any character that is not a digit, equivalent to [^\d] and [^0-9]
• \w matches any word character, equivalent to [a-zA-Z0-9_]
• \W matches any character that is not a word character, equivalent to [^\w]
• \s matches any whitespace character, like tabs, spaces, line breaks.
• \S matches any character that is not a whitespace character

INFO

• In .NET, \w matches not only [a-zA-Z0-9_], it also includes other letters like Cyrillic and Thai.
• \s also matches whitespace characters in Unicode in .NET and JavaScript