Matching Rules for Extended Regular
Expressions
The following rules apply within an Extended
Regular Expression:
- An ordinary character matches itself. The
simplest form of regular expression is a string of
characters with no special meaning.
- A special character preceded by a
backslash matches itself. The special characters are:
. [ \ * ^ $ ( ) + ? { |
- A period (.) without a backslash matches
any character except the null character.
- An expression within square brackets ( [ ]
), a bracket expression, matches a single character or
collating element.

Regular
Expressions

Additional Syntax
Specifiers for Extended Regular Expressions