Regular Expressions

## Example Regular Expressions

The following are regular expression examples which will match:

- An entire line.

            ^.*$

- Blank lines.

            ^$

- Whitespace on a line.

            \s+

- Whitespace across lines.

            (?n\s+)

- Whitespace that spans at least two lines. Note minimal matching `*?' quantifier.

            (?n\s*?\n\s*)

- IP address (not robust).

            (?:\d{1,3}(?:\.\d{1,3}){3})

- Two character US Postal state abbreviations (includes territories).

            [ACDF-IK-PR-W][A-Z]

- Web addresses.

            (?:http://)?www\.\S+

- Case insensitive double words across line breaks.

            (?i(?n<(\S+)\s+\1>))

- Upper case words with possible punctuation.

            <[A-Z][^a-z\s]*>