Regexp - Dot (Single Character pattern)

About

Dot . in a regular expression matches any character in the supported character set with this characteristic, by default:

• newline characters are not included without setting a flag. See matchnewline
• the match stops at the first occurrence. See greedy mode versus lazy mode that will stop at the first one.

Dot has no special meaning in a character class.

Articles Related

Configuration

Match Newline (DOTALL)

Dot does not match newlines by default, a modifier must be set when running the matching function.

Java Example with the DOTALL flag:

• A pattern that capture the content between two XML nodes even if there is new line in there.

Pattern pattern = Pattern.compile("<top>(.*?)</top>",Pattern.DOTALL);

Stop at

last occurrence (Greedy mode - default)

Dot will match all character with the default greedy matching mode.

First Occurrence (Lazy)

If you want to made it lazy, you need to add a ? after the quantifier. See Regular Expression - (Lazy|Reluctant) Quantifier

Example

Basic

.at matches any three-character string ending with at, including:

• hat,
• cat,
• and bat.

Exclude newlines from the negation

With dot all, a common mistake is to assume that a negated character set like [^#] will also not match newlines.

In order to exclude newlines, they must be added to the set.

Example: Every characters that is not ( # and Linux EOL \n) will be expressed as:

[^#\n]

Documentation / Reference

• Php Dot