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662 lines
23 KiB
Plaintext
662 lines
23 KiB
Plaintext
@c Copyright (C) 1994, 1996, 1998, 2000-2001, 2003-2007, 2009-2017 Free
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@c Software Foundation, Inc.
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@c
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@c Permission is granted to copy, distribute and/or modify this document
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@c under the terms of the GNU Free Documentation License, Version 1.3 or
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@c any later version published by the Free Software Foundation; with no
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@c Invariant Sections, no Front-Cover Texts, and no Back-Cover
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@c Texts. A copy of the license is included in the ``GNU Free
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@c Documentation License'' file as part of this distribution.
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@c this regular expression description is for: generic
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@menu
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* awk regular expression syntax::
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* egrep regular expression syntax::
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* ed regular expression syntax::
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* emacs regular expression syntax::
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* gnu-awk regular expression syntax::
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* grep regular expression syntax::
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* posix-awk regular expression syntax::
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* posix-basic regular expression syntax::
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* posix-egrep regular expression syntax::
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* posix-extended regular expression syntax::
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* posix-minimal-basic regular expression syntax::
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* sed regular expression syntax::
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@end menu
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@node awk regular expression syntax
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@subsection @samp{awk} regular expression syntax
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The character @samp{.} matches any single character except the null character.
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@table @samp
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@item +
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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@item ?
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indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
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@item \+
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matches a @samp{+}
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@item \?
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matches a @samp{?}.
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@end table
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} can be used to quote the following character. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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GNU extensions are not supported and so @samp{\w}, @samp{\W}, @samp{\<}, @samp{\>}, @samp{\b}, @samp{\B}, @samp{\`}, and @samp{\'} match @samp{w}, @samp{W}, @samp{<}, @samp{>}, @samp{b}, @samp{B}, @samp{`}, and @samp{'} respectively.
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Grouping is performed with parentheses @samp{()}. An unmatched @samp{)} matches just itself. A backslash followed by a digit matches that digit.
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The alternation operator is @samp{|}.
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The characters @samp{^} and @samp{$} always represent the beginning and end of a string respectively, except within square brackets. Within brackets, @samp{^} can be used to invert the membership of the character class being specified.
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@samp{*}, @samp{+} and @samp{?} are special at any point in a regular expression except:
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@enumerate
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@item At the beginning of a regular expression
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@item After an open-group, signified by
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@samp{(}
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@item After the alternation operator @samp{|}
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@end enumerate
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The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
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@node egrep regular expression syntax
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@subsection @samp{egrep} regular expression syntax
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The character @samp{.} matches any single character.
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@table @samp
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@item +
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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@item ?
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indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
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@item \+
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matches a @samp{+}
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@item \?
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matches a @samp{?}.
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@end table
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} is taken literally. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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GNU extensions are supported:
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@enumerate
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@item @samp{\w} matches a character within a word
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@item @samp{\W} matches a character which is not within a word
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@item @samp{\<} matches the beginning of a word
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@item @samp{\>} matches the end of a word
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@item @samp{\b} matches a word boundary
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@item @samp{\B} matches characters which are not a word boundary
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@item @samp{\`} matches the beginning of the whole input
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@item @samp{\'} matches the end of the whole input
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@end enumerate
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Grouping is performed with parentheses @samp{()}. An unmatched @samp{)} matches just itself. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{(}.
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The alternation operator is @samp{|}.
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The characters @samp{^} and @samp{$} always represent the beginning and end of a string respectively, except within square brackets. Within brackets, @samp{^} can be used to invert the membership of the character class being specified.
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The characters @samp{*}, @samp{+} and @samp{?} are special anywhere in a regular expression.
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Intervals are specified by @samp{@{} and @samp{@}}. Invalid intervals are treated as literals, for example @samp{a@{1} is treated as @samp{a\@{1}
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The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
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@node ed regular expression syntax
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@subsection @samp{ed} regular expression syntax
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The character @samp{.} matches any single character except the null character.
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@table @samp
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@item \+
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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@item \?
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indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
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@item + and ?
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match themselves.
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@end table
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} is taken literally. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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GNU extensions are supported:
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@enumerate
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@item @samp{\w} matches a character within a word
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@item @samp{\W} matches a character which is not within a word
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@item @samp{\<} matches the beginning of a word
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@item @samp{\>} matches the end of a word
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@item @samp{\b} matches a word boundary
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@item @samp{\B} matches characters which are not a word boundary
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@item @samp{\`} matches the beginning of the whole input
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@item @samp{\'} matches the end of the whole input
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@end enumerate
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Grouping is performed with backslashes followed by parentheses @samp{\(}, @samp{\)}. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{\(}.
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The alternation operator is @samp{\|}.
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The character @samp{^} only represents the beginning of a string when it appears:
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@enumerate
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@item
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At the beginning of a regular expression
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@item After an open-group, signified by
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@samp{\(}
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@item After the alternation operator @samp{\|}
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@end enumerate
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The character @samp{$} only represents the end of a string when it appears:
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@enumerate
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@item At the end of a regular expression
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@item Before a close-group, signified by
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@samp{\)}
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@item Before the alternation operator @samp{\|}
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@end enumerate
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@samp{\*}, @samp{\+} and @samp{\?} are special at any point in a regular expression except:
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@enumerate
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@item At the beginning of a regular expression
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@item After an open-group, signified by
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@samp{\(}
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@item After the alternation operator @samp{\|}
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@end enumerate
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Intervals are specified by @samp{\@{} and @samp{\@}}. Invalid intervals such as @samp{a\@{1z} are not accepted.
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The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
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@node emacs regular expression syntax
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@subsection @samp{emacs} regular expression syntax
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The character @samp{.} matches any single character except newline.
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@table @samp
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@item +
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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@item ?
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indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
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@item \+
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matches a @samp{+}
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@item \?
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matches a @samp{?}.
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@end table
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are ignored. Within square brackets, @samp{\} is taken literally. Character classes are not supported, so for example you would need to use @samp{[0-9]} instead of @samp{[[:digit:]]}.
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GNU extensions are supported:
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@enumerate
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@item @samp{\w} matches a character within a word
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@item @samp{\W} matches a character which is not within a word
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@item @samp{\<} matches the beginning of a word
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@item @samp{\>} matches the end of a word
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@item @samp{\b} matches a word boundary
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@item @samp{\B} matches characters which are not a word boundary
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@item @samp{\`} matches the beginning of the whole input
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@item @samp{\'} matches the end of the whole input
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@end enumerate
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Grouping is performed with backslashes followed by parentheses @samp{\(}, @samp{\)}. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{\(}.
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The alternation operator is @samp{\|}.
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The character @samp{^} only represents the beginning of a string when it appears:
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@enumerate
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@item
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At the beginning of a regular expression
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@item After an open-group, signified by
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@samp{\(}
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@item After the alternation operator @samp{\|}
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@end enumerate
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The character @samp{$} only represents the end of a string when it appears:
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@enumerate
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@item At the end of a regular expression
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@item Before a close-group, signified by
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@samp{\)}
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@item Before the alternation operator @samp{\|}
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@end enumerate
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@samp{*}, @samp{+} and @samp{?} are special at any point in a regular expression except:
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@enumerate
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@item At the beginning of a regular expression
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@item After an open-group, signified by
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@samp{\(}
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@item After the alternation operator @samp{\|}
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@end enumerate
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The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
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@node gnu-awk regular expression syntax
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@subsection @samp{gnu-awk} regular expression syntax
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The character @samp{.} matches any single character.
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@table @samp
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@item +
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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@item ?
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indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
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@item \+
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matches a @samp{+}
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@item \?
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matches a @samp{?}.
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@end table
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} can be used to quote the following character. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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GNU extensions are supported:
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@enumerate
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@item @samp{\w} matches a character within a word
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@item @samp{\W} matches a character which is not within a word
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@item @samp{\<} matches the beginning of a word
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@item @samp{\>} matches the end of a word
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@item @samp{\b} matches a word boundary
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@item @samp{\B} matches characters which are not a word boundary
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@item @samp{\`} matches the beginning of the whole input
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@item @samp{\'} matches the end of the whole input
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@end enumerate
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Grouping is performed with parentheses @samp{()}. An unmatched @samp{)} matches just itself. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{(}.
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The alternation operator is @samp{|}.
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The characters @samp{^} and @samp{$} always represent the beginning and end of a string respectively, except within square brackets. Within brackets, @samp{^} can be used to invert the membership of the character class being specified.
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|
@samp{*}, @samp{+} and @samp{?} are special at any point in a regular expression except:
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@enumerate
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@item At the beginning of a regular expression
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@item After an open-group, signified by
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@samp{(}
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@item After the alternation operator @samp{|}
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@end enumerate
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Intervals are specified by @samp{@{} and @samp{@}}. Invalid intervals are treated as literals, for example @samp{a@{1} is treated as @samp{a\@{1}
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The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
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@node grep regular expression syntax
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@subsection @samp{grep} regular expression syntax
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The character @samp{.} matches any single character.
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@table @samp
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@item \+
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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@item \?
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indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
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@item + and ?
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match themselves.
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@end table
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|
|
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} is taken literally. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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|
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GNU extensions are supported:
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@enumerate
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|
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@item @samp{\w} matches a character within a word
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|
|
|
@item @samp{\W} matches a character which is not within a word
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|
|
|
@item @samp{\<} matches the beginning of a word
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|
@item @samp{\>} matches the end of a word
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|
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|
@item @samp{\b} matches a word boundary
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@item @samp{\B} matches characters which are not a word boundary
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@item @samp{\`} matches the beginning of the whole input
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@item @samp{\'} matches the end of the whole input
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@end enumerate
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|
|
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Grouping is performed with backslashes followed by parentheses @samp{\(}, @samp{\)}. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{\(}.
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|
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|
The alternation operator is @samp{\|}.
|
|
|
|
The character @samp{^} only represents the beginning of a string when it appears:
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@enumerate
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|
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|
@item
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At the beginning of a regular expression
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|
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@item After an open-group, signified by
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@samp{\(}
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@item After a newline
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@item After the alternation operator @samp{\|}
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@end enumerate
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The character @samp{$} only represents the end of a string when it appears:
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@enumerate
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@item At the end of a regular expression
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@item Before a close-group, signified by
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@samp{\)}
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@item Before a newline
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@item Before the alternation operator @samp{\|}
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@end enumerate
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@samp{\*}, @samp{\+} and @samp{\?} are special at any point in a regular expression except:
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@enumerate
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|
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@item At the beginning of a regular expression
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|
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@item After an open-group, signified by
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@samp{\(}
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@item After a newline
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@item After the alternation operator @samp{\|}
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@end enumerate
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|
|
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Intervals are specified by @samp{\@{} and @samp{\@}}. Invalid intervals such as @samp{a\@{1z} are not accepted.
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|
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|
The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
|
|
|
|
|
|
@node posix-awk regular expression syntax
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|
@subsection @samp{posix-awk} regular expression syntax
|
|
|
|
|
|
The character @samp{.} matches any single character except the null character.
|
|
|
|
|
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@table @samp
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|
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|
@item +
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indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
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|
@item ?
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|
indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
|
|
@item \+
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|
matches a @samp{+}
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|
@item \?
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|
matches a @samp{?}.
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|
@end table
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|
|
|
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|
Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} can be used to quote the following character. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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|
|
|
GNU extensions are not supported and so @samp{\w}, @samp{\W}, @samp{\<}, @samp{\>}, @samp{\b}, @samp{\B}, @samp{\`}, and @samp{\'} match @samp{w}, @samp{W}, @samp{<}, @samp{>}, @samp{b}, @samp{B}, @samp{`}, and @samp{'} respectively.
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|
|
|
Grouping is performed with parentheses @samp{()}. An unmatched @samp{)} matches just itself. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{(}.
|
|
|
|
The alternation operator is @samp{|}.
|
|
|
|
The characters @samp{^} and @samp{$} always represent the beginning and end of a string respectively, except within square brackets. Within brackets, @samp{^} can be used to invert the membership of the character class being specified.
|
|
|
|
@samp{*}, @samp{+} and @samp{?} are special at any point in a regular expression except the following places, where they are not allowed:
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|
@enumerate
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|
@item At the beginning of a regular expression
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|
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|
@item After an open-group, signified by
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|
@samp{(}
|
|
@item After the alternation operator @samp{|}
|
|
|
|
@end enumerate
|
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|
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Intervals are specified by @samp{@{} and @samp{@}}. Invalid intervals are treated as literals, for example @samp{a@{1} is treated as @samp{a\@{1}
|
|
|
|
The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
|
|
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|
|
@node posix-basic regular expression syntax
|
|
@subsection @samp{posix-basic} regular expression syntax
|
|
This is a synonym for ed.
|
|
@node posix-egrep regular expression syntax
|
|
@subsection @samp{posix-egrep} regular expression syntax
|
|
This is a synonym for egrep.
|
|
@node posix-extended regular expression syntax
|
|
@subsection @samp{posix-extended} regular expression syntax
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|
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|
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The character @samp{.} matches any single character except the null character.
|
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|
|
@table @samp
|
|
|
|
@item +
|
|
indicates that the regular expression should match one or more occurrences of the previous atom or regexp.
|
|
@item ?
|
|
indicates that the regular expression should match zero or one occurrence of the previous atom or regexp.
|
|
@item \+
|
|
matches a @samp{+}
|
|
@item \?
|
|
matches a @samp{?}.
|
|
@end table
|
|
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|
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Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} is taken literally. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
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|
|
|
GNU extensions are supported:
|
|
@enumerate
|
|
|
|
@item @samp{\w} matches a character within a word
|
|
|
|
@item @samp{\W} matches a character which is not within a word
|
|
|
|
@item @samp{\<} matches the beginning of a word
|
|
|
|
@item @samp{\>} matches the end of a word
|
|
|
|
@item @samp{\b} matches a word boundary
|
|
|
|
@item @samp{\B} matches characters which are not a word boundary
|
|
|
|
@item @samp{\`} matches the beginning of the whole input
|
|
|
|
@item @samp{\'} matches the end of the whole input
|
|
|
|
@end enumerate
|
|
|
|
|
|
Grouping is performed with parentheses @samp{()}. An unmatched @samp{)} matches just itself. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{(}.
|
|
|
|
The alternation operator is @samp{|}.
|
|
|
|
The characters @samp{^} and @samp{$} always represent the beginning and end of a string respectively, except within square brackets. Within brackets, @samp{^} can be used to invert the membership of the character class being specified.
|
|
|
|
@samp{*}, @samp{+} and @samp{?} are special at any point in a regular expression except the following places, where they are not allowed:
|
|
@enumerate
|
|
|
|
@item At the beginning of a regular expression
|
|
|
|
@item After an open-group, signified by
|
|
@samp{(}
|
|
@item After the alternation operator @samp{|}
|
|
|
|
@end enumerate
|
|
|
|
|
|
Intervals are specified by @samp{@{} and @samp{@}}. Invalid intervals such as @samp{a@{1z} are not accepted.
|
|
|
|
The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
|
|
|
|
|
|
@node posix-minimal-basic regular expression syntax
|
|
@subsection @samp{posix-minimal-basic} regular expression syntax
|
|
|
|
|
|
The character @samp{.} matches any single character except the null character.
|
|
|
|
|
|
|
|
Bracket expressions are used to match ranges of characters. Bracket expressions where the range is backward, for example @samp{[z-a]}, are invalid. Within square brackets, @samp{\} is taken literally. Character classes are supported; for example @samp{[[:digit:]]} will match a single decimal digit.
|
|
|
|
GNU extensions are supported:
|
|
@enumerate
|
|
|
|
@item @samp{\w} matches a character within a word
|
|
|
|
@item @samp{\W} matches a character which is not within a word
|
|
|
|
@item @samp{\<} matches the beginning of a word
|
|
|
|
@item @samp{\>} matches the end of a word
|
|
|
|
@item @samp{\b} matches a word boundary
|
|
|
|
@item @samp{\B} matches characters which are not a word boundary
|
|
|
|
@item @samp{\`} matches the beginning of the whole input
|
|
|
|
@item @samp{\'} matches the end of the whole input
|
|
|
|
@end enumerate
|
|
|
|
|
|
Grouping is performed with backslashes followed by parentheses @samp{\(}, @samp{\)}. A backslash followed by a digit acts as a back-reference and matches the same thing as the previous grouped expression indicated by that number. For example @samp{\2} matches the second group expression. The order of group expressions is determined by the position of their opening parenthesis @samp{\(}.
|
|
|
|
|
|
|
|
The character @samp{^} only represents the beginning of a string when it appears:
|
|
@enumerate
|
|
|
|
@item
|
|
At the beginning of a regular expression
|
|
|
|
@item After an open-group, signified by
|
|
@samp{\(}
|
|
|
|
@end enumerate
|
|
|
|
|
|
The character @samp{$} only represents the end of a string when it appears:
|
|
@enumerate
|
|
|
|
@item At the end of a regular expression
|
|
|
|
@item Before a close-group, signified by
|
|
@samp{\)}
|
|
@end enumerate
|
|
|
|
|
|
|
|
|
|
Intervals are specified by @samp{\@{} and @samp{\@}}. Invalid intervals such as @samp{a\@{1z} are not accepted.
|
|
|
|
The longest possible match is returned; this applies to the regular expression as a whole and (subject to this constraint) to subexpressions within groups.
|
|
|
|
|
|
@node sed regular expression syntax
|
|
@subsection @samp{sed} regular expression syntax
|
|
This is a synonym for ed.
|