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6.3. Metacharacters

6.3.1. Search Patterns

The characters in the following table have special meaning only in search patterns.


Match any single character except newline. Can match newline in awk.


Match any number (or none) of the single character that immediately precedes it. The preceding character can also be a regular expression; e.g., since . (dot) means any character, .* means “match any number of any character.”


Match the following regular expression at the beginning of the line or string.


Match the preceding regular expression at the end of the line or string.

[ ]

Match any one of the enclosed characters.

A hyphen (-) indicates a range of consecutive characters. A circumflex (^) as the first character in the brackets reverses the sense: it matches any one character not in the list. A hyphen or close bracket (]) as the first character is treated as a member of the list. All other metacharacters are treated as members of the list (i.e., literally).


Match a range of occurrences of the single character that immediately precedes it. The preceding character can also be a metacharacter. {n} matches exactly n occurrences, {n,} matches at least n occurrences, and {n,m} matches any number of occurrences between n and m. n and m must be between 0 and 255, inclusive.


Just like {n,m}, above, but with backslashes in front of the braces.

\Turn off the special meaning of the character that follows.
\( \)

Save the pattern enclosed between \( and \) into a special holding space. Up to nine patterns can be saved on a single line. The text matched by the subpatterns can be “replayed” in substitutions by the escape sequences \1 to \9.


Replay the nth subpattern enclosed in \( and \) into the pattern at this point. n is a number from 1 to 9, with 1 starting on the left. See the following Examples.

\< \>

Match characters at beginning (\<) or end (\>) of a word.

+Match one or more instances of preceding regular expression.

Match zero or one instances of preceding regular expression.


Match the regular expression specified before or after.

( )

Apply a match to the enclosed group of regular expressions.

Many Unix systems allow the use of POSIX “character classes” within the square brackets that enclose a group of characters. These classes, listed here, are typed enclosed in [: and :]. For example, [[:alnum:]] matches a single alphanumeric character.

ClassCharacters Matched

Alphanumeric characters


Alphabetic characters


Space or tab


Control characters


Decimal digits


Nonspace characters


Lowercase characters


Printable characters


Whitespace characters


Uppercase characters


Hexadecimal digits

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