regexprops, generated by findutils helper

diff --git a/doc/README b/doc/README
index a50ddda..551f539 100644 (file)
--- a/doc/README
+++ b/doc/README
@@ -1,16 +1 @@
-Sketchy start at information on using files in gnulib.
-
-for mktemp, need these files (including adding to EXTRA_DIST):
-$GNULIBSRC/m4/check-decl.m4    m4
-$GNULIBSRC/m4/mkstemp.m4       m4
-$GNULIBSRC/m4/prereq.m4                m4
-$GNULIBSRC/lib/tempname.c      lib
-$GNULIBSRC/lib/mkstemp.c       lib
-
-then in configure.ac:
-AC_DEFUN([texinfo_MACROS],
-[
-  AC_REQUIRE([gl_PREREQ_TEMPNAME])dnl for mkstemp
-  AC_REQUIRE([UTILS_FUNC_MKSTEMP])
-])dnl
-texinfo_MACROS
+regexprops-generic.texi is generated via a utility in findutils.

diff --git a/doc/gnulib.texi b/doc/gnulib.texi
index 8e434a2..cc82699 100644 (file)
--- a/doc/gnulib.texi
+++ b/doc/gnulib.texi
@@ -1,5 +1,5 @@
 \input texinfo   @c -*-texinfo-*-
-@comment $Id: gnulib.texi,v 1.13 2005-07-16 19:41:33 jas Exp $
+@comment $Id: gnulib.texi,v 1.14 2005-07-27 00:16:01 karl Exp $
 @comment %**start of header
 @setfilename gnulib.info
 @settitle GNU Gnulib
@@ -7,7 +7,7 @@
 @syncodeindex pg cp
 @comment %**end of header
 
-@set UPDATED $Date: 2005-07-16 19:41:33 $
+@set UPDATED $Date: 2005-07-27 00:16:01 $
 
 @copying
 This manual is for GNU Gnulib (updated @value{UPDATED}),
@@ -87,6 +87,7 @@ Getting started:
 * inet_ntoa::
 * Out of memory handling::
 * Library version handling::
+* Regular expressions::
 @end menu
 
 
@@ -346,6 +347,17 @@ Typical uses look like:
 @end example
 
 
+@node Regular expressions
+@section Regular expressions
+
+Gnulib supports many different types of regular expressions; although
+the underlying features are the same or identical, the syntax used
+varies.  The descriptions given here for the different types are
+generated automatically.
+
+@include regexprops-generic.texi
+
+
 @node Invoking gnulib-tool
 @chapter Invoking gnulib-tool
 

diff --git a/doc/regexprops-generic.texi b/doc/regexprops-generic.texi
new file mode 100644 (file)
index 0000000..cad909b
--- /dev/null
+++ b/doc/regexprops-generic.texi
@@ -0,0 +1,703 @@
+@menu
+* awk regular expression syntax::
+* egrep regular expression syntax::
+* ed regular expression syntax::
+* emacs regular expression syntax::
+* gnu-awk regular expression syntax::
+* grep regular expression syntax::
+* posix-awk regular expression syntax::
+* posix-basic regular expression syntax::
+* posix-egrep regular expression syntax::
+* posix-extended regular expression syntax::
+* posix-minimal-basic regular expression syntax::
+* sed regular expression syntax::
+@end menu
+
+@node awk regular expression syntax
+@subsection @samp{awk} regular expression syntax
+
+
+The character @samp{.} matches any single character except the null character.  
+
+
+@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
+
+
+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 not supported, so for example you would need to use @samp{[0-9]} instead of @samp{[[:digit:]]}.  
+
+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.  
+
+Grouping is performed with parentheses @samp{()}.  An unmatched @samp{)} matches just itself.  A backslash followed by a digit matches that digit.  
+
+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:
+@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
+
+
+
+
+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 egrep regular expression syntax
+@subsection @samp{egrep} regular expression syntax
+
+
+The character @samp{.} matches any single character except newline.  
+
+
+@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
+
+
+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 supported; for example @samp{[[:digit:]]} will match a single decimal digit.  Non-matching lists @samp{[^@dots{}]} do not ever match newline.  
+
+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{()}.  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.  
+
+The characters @samp{*}, @samp{+} and @samp{?} are special anywhere in a regular expression.  
+
+
+
+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 ed regular expression syntax
+@subsection @samp{ed} regular expression syntax
+
+
+The character @samp{.} matches any single character except the null character.  
+
+
+@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 + and ? 
+match themselves.  
+@end table
+
+
+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 alternation operator is @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{\(}
+
+@item After the alternation operator @samp{\|}
+
+@end enumerate
+
+
+The character @samp{$} only represents the end of a string when it appears:
+@enumerate
+
+@item At the end of a regular expression
+
+@item Before an close-group, signified by 
+@samp{\)}
+@item Before the alternation operator @samp{\|}
+
+@end enumerate
+
+
+@samp{\*}, @samp{\+} and @samp{\?} are special at any point in a regular expression except:
+@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 emacs regular expression syntax
+@subsection @samp{emacs} regular expression syntax
+
+
+The character @samp{.} matches any single character except newline.  
+
+
+@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
+
+
+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:]]}.  
+
+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 alternation operator is @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{\(}
+
+@item After the alternation operator @samp{\|}
+
+@end enumerate
+
+
+The character @samp{$} only represents the end of a string when it appears:
+@enumerate
+
+@item At the end of a regular expression
+
+@item Before an close-group, signified by 
+@samp{\)}
+@item Before the alternation operator @samp{\|}
+
+@end enumerate
+
+
+@samp{*}, @samp{+} and @samp{?} are special at any point in a regular expression except:
+@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
+
+
+
+
+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 gnu-awk regular expression syntax
+@subsection @samp{gnu-awk} regular expression syntax
+
+
+The character @samp{.} matches any single character.  
+
+
+@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
+
+
+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.  
+
+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:
+@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
+
+
+
+
+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 grep regular expression syntax
+@subsection @samp{grep} regular expression syntax
+
+
+The character @samp{.} matches any single character except newline.  
+
+
+@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 + and ? 
+match themselves.  
+@end table
+
+
+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 supported; for example @samp{[[:digit:]]} will match a single decimal digit.  Non-matching lists @samp{[^@dots{}]} do not ever match newline.  
+
+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 alternation operator is @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{\(}
+
+@item After a newline
+
+@item After the alternation operator @samp{\|}
+
+@end enumerate
+
+
+The character @samp{$} only represents the end of a string when it appears:
+@enumerate
+
+@item At the end of a regular expression
+
+@item Before an close-group, signified by 
+@samp{\)}
+@item Before a newline
+
+@item Before the alternation operator @samp{\|}
+
+@end enumerate
+
+
+@samp{\*}, @samp{\+} and @samp{\?} are special at any point in a regular expression except:
+@enumerate
+
+@item At the beginning of a regular expression
+
+@item After an open-group, signified by 
+@samp{\(}
+@item After a newline
+
+@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-awk regular expression syntax
+@subsection @samp{posix-awk} regular expression syntax
+
+
+The character @samp{.} matches any single character except the null character.  
+
+
+@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
+
+
+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.  
+
+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.  
+
+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 illegal:
+@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-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
+
+
+The character @samp{.} matches any single character except newline.  
+
+
+@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
+
+
+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 supported; for example @samp{[[:digit:]]} will match a single decimal digit.  Non-matching lists @samp{[^@dots{}]} do not ever match newline.  
+
+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{()}.  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.  
+
+The characters @samp{*}, @samp{+} and @samp{?} are special anywhere in a regular expression.  
+
+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.  
+
+
+@node posix-extended regular expression syntax
+@subsection @samp{posix-extended} regular expression syntax
+
+
+The character @samp{.} matches any single character except the null character.  
+
+
+@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
+
+
+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 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 illegal:
+@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{\(}
+
+@end enumerate
+
+
+The character @samp{$} only represents the end of a string when it appears:
+@enumerate
+
+@item At the end of a regular expression
+
+@item Before an close-group, signified by 
+@samp{\)}
+@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.
\ No newline at end of file