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Full Discussion: Regular expression with SED
Top Forums Shell Programming and Scripting Regular expression with SED Post 302387113 by Corona688 on Thursday 14th of January 2010 01:14:05 PM
Old 01-14-2010
Correct, it matches 0 or more charcters of that. The brackets surrounding it have a special meaning when you run sed with -r: it remembers that specific section in order to refer to it later. We match the entire string and keep the bit we want with brackets.

The .*$ lets the pattern match the entire string so it can replace the entire string. We want to delete everything after the hello, so we have to match it too.

Having matched the whole string, we keep the part we want as a backreference. \1 refers to the first section in brackets, \2 the second, and so forth. It needs the -r flag to work.

The last 'g' lets it match the pattern more than once if possible. Observe:
Code:
$ echo ababab | sed 's/a/b/'
bbabab
$ echo ababab | sed 's/a/b/g'
bbbbbb
$

Last edited by Corona688; 01-14-2010 at 02:20 PM..
 

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LEARN ABOUT OSX

ppi::token::regexp

PPI::Token::Regexp(3)					User Contributed Perl Documentation				     PPI::Token::Regexp(3)

NAME

       PPI::Token::Regexp - Regular expression abstract base class

INHERITANCE

	 PPI::Token::Regexp
	 isa PPI::Token
	     isa PPI::Element

DESCRIPTION

       The "PPI::Token::Regexp" class is never instantiated, and simply provides a common abstract base class for the three regular expression
       classes. These being:

       m// - PPI::Token::Regexp::Match
       s/// - PPI::Token::Regexp::Substitute
       tr/// - PPI::Token::Regexp::Transliterate

       The names are hopefully obvious enough not to have to explain what each class is. See their pages for more details.

       To save some confusion, it's worth pointing out here that "qr//" is not a regular expression (which PPI takes to mean something that will
       actually examine or modify a string), but rather a quote-like operator that acts as a constructor for compiled Regexp objects.

METHODS

       The following methods are inherited by this class' offspring:

   get_match_string
       The "get_match_string" method returns the portion of the regexp that performs the match.

   get_substitute_string
       The "get_substitute_string" method returns the portion of the regexp that is substituted for the match, if any.	If the regexp does not
       substitute, "undef" is returned.

   get_modifiers
       The "get_modifiers" method returns the modifiers of the regexp.

   get_delimiters
       The "get_delimiters" method returns the delimiters of the regexp as an array. The first element is the delimiters of the match string, and
       the second element (if any) is the delimiters of the substitute string (if any).

SUPPORT

       See the support section in the main module.

AUTHOR

       Adam Kennedy <adamk@cpan.org>

COPYRIGHT

       Copyright 2001 - 2011 Adam Kennedy.

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

       The full text of the license can be found in the LICENSE file included with this module.

perl v5.16.2							    2011-02-25						     PPI::Token::Regexp(3)
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