Regular Expressions

# Regular Expressions |

Regular expression is a notation for patterns of text, as opposed to exact strings of characters. The notation uses literal characters and metacharacters. Every character which does not have special meaning in the regular-expression syntax is a literal character and matches an occurrence of that character. For example, letters and numbers are literal characters. A metacharacter is a symbol with special meaning (an operator or delimiter) in the regular-expression syntax.
. | Wildcard: any character
* | Repeat: zero or more occurrences of previous character or class
^ | Line position: beginning of line
$ | Line position: end of line
[class] | Character class: any character in the set
[^class] | Inverse class: any character not in the set
[x-y] | Range: any characters within the specified range
\x | Escape: literal use of metacharacter x
\<xyz | Word position: beginning of the word
xyz\> | Word position: end of the word
For example, the following regular expression .* matches any string of characters, ^a matches any string beginning with character a.