9.3 Metacharacters
The following characters have special meaning in search patterns:
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.
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Match any single character except newline.
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*
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Match any number (or none) of the single character that immediately
precedes it. The preceding character also can be a regular expression
(e.g., since . (dot) means any character, .* means match any number of any
character—except newlines).
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^
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Match the beginning of the line or string.
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$
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Match the end of the line or string.
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[ ]
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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.
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[^ ]
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Match anything except enclosed characters.
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\{n,m\}
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Match a range of occurrences of the single character that immediately
precedes it. The preceding character also can be a regular
expression. \{n\} matches exactly
n occurrences, \{n,\} matches at least
n occurrences, and \{n,m\} matches any number of occurrences between
n and m.
|
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{n,m}
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Like \{n,m\}. Available in grep by default and in gawk with the -Wre-interval option.
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\
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Turn off the special meaning of the character that follows.
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\( \)
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Save the matched text enclosed between \( and \) in
a special holding space. Up to nine patterns can be saved on a single
line. They can be "replayed" in the
same pattern or within substitutions by the escape sequences
\1 to \9.
|
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\n
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Reuse matched text stored in nth \( \).
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\<
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Match the beginning of a word.
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\>
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Match the end of a word.
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+
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Match one or more instances of preceding regular expression.
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?
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Match zero or one instance of preceding regular expression.
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|
|
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Match the regular expression specified before or after.
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( )
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In egrep and gawk, group regular expressions.
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Many utilities support POSIX character
lists, which are useful for matching non-ASCII characters in
languages other than English. These lists are recognized only within
[ ] ranges. A typical use would be
[[:lower:]], which in English is the
same as [a-z].
The following table lists POSIX character lists:
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[:alnum:]
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Alphanumeric characters
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[:alpha:]
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Alphabetic characters, uppercase and lowercase
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[:blank:]
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Printable whitespace: spaces and tabs but not control characters
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[:cntrl:]
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Control characters, such as ^A
through ^Z
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[:digit:]
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Decimal digits
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[:graph:]
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Printable characters, excluding whitespace
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[:lower:]
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Lowercase alphabetic characters
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[:print:]
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Printable characters, including whitespace but not control characters
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[:punct:]
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Punctuation, a subclass of printable characters
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[:space:]
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Whitespace, including spaces, tabs, and some control characters
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[:upper:]
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Uppercase alphabetic characters
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[:xdigit:]
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Hexadecimal digits
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The following characters have special meaning in replacement patterns:
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\
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Turn off the special meaning of the character that follows.
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\n
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Restore the nth pattern previously saved by
\( and \). n is a number from 1
to 9, matching the patterns searched sequentially from left to right.
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&
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Reuse the search pattern as part of the replacement pattern.
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~
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Reuse the previous replacement pattern in the current replacement
pattern.
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\e
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End replacement pattern started by \L or \U.
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\E
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End replacement pattern started by \L or \U.
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\l
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Convert first character of replacement pattern to lowercase.
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\L
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Convert replacement pattern to lowercase.
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\u
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Convert first character of replacement pattern to uppercase.
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\U
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Convert replacement pattern to uppercase.
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