I just wanted to give myself a reference for a regular expression cheat sheet. This is much easier then forgetting and having to google for what I need. Pretty much all you ever need to know to setup a regexp.
. |
Matches any single character (many applications exclude newlines, and exactly which characters are considered newlines is flavor, character encoding, and platform specific, but it is safe to assume that the line feed character is included). Within POSIX bracket expressions, the dot character matches a literal dot. For example, a.c matches “abc“, etc., but [a.c] matches only “a“, “.“, or “c“. |
[ ] |
A bracket expression. Matches a single character that is contained within the brackets. For example, [abc] matches “a“, “b“, or “c“. [a-z] specifies a range which matches any lowercase letter from “a” to “z“. These forms can be mixed: [abcx-z] matches “a“, “b“, “c“, “x“, “y“, and “z“, as does [a-cx-z].
The |
[^ ] |
Matches a single character that is not contained within the brackets. For example, [^abc] matches any character other than “a“, “b“, or “c“. [^a-z] matches any single character that is not a lowercase letter from “a” to “z“. As above, literal characters and ranges can be mixed. |
^ |
Matches the starting position within the string. In line-based tools, it matches the starting position of any line. |
$ |
Matches the ending position of the string or the position just before a string-ending newline. In line-based tools, it matches the ending position of any line. |
\( \) |
Defines a marked subexpression. The string matched within the parentheses can be recalled later (see the next entry, \n). A marked subexpression is also called a block or capturing group. |
\n |
Matches what the nth marked subexpression matched, where n is a digit from 1 to 9. This construct is theoretically irregular and was not adopted in the POSIX ERE syntax. Some tools allow referencing more than nine capturing groups. |
* |
Matches the preceding element zero or more times. For example, ab*c matches “ac“, “abc“, “abbbc“, etc. [xyz]* matches “”, “x“, “y“, “z“, “zx“, “zyx“, “xyzzy“, and so on. \(ab\)* matches “”, “ab“, “abab“, “ababab“, and so on. |
\{m,n\} |
Matches the preceding element at least m and not more than n times. For example, a\{3,5\} matches only “aaa“, “aaaa“, and “aaaaa“. This is not found in a few, older instances of regular expressions. |
