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Full Discussion: Regex learning.
Top Forums Shell Programming and Scripting Regex learning. Post 303044737 by RavinderSingh13 on Tuesday 3rd of March 2020 12:09:53 AM
Old 03-03-2020
Hello All,

Learnt an example of Lazy match in Regex in Perl, so thought to share here.
Let's say following is Input_file.

Code:
cat Input_file
abcdtest123^ DUMMYtestabcd12234 DUMMY bla blabla12231311313blabla bla.....,,,,,bla
test132131 ^ DUMMY blabla1213 121313_ 131y7351eg1eub wdfwfknfidh28e7ty;;;

Now we would like to have data between first occurrence of ^ to DUMMY , then we could use Lazy match like as follows:

Code:
perl -pe 's|(\^.*?DUMMY\s+)(.*)| new_text_here.... \2|'  Input_file

Output will be as follows for mentioned sample:
Code:
abcdtest123 new_text_here.... bla blabla12231311313blabla bla.....,,,,,bla
test132131  new_text_here.... blabla1213 121313_ 131y7351eg1eub wdfwfknfidh28e7ty;;;

Why is Lazy match Good here? Because .* is a GREEDY match and matches anything till last occurrence of any mentioned character etc but using Lazy match .*?DUMMY\s+ it matches very first occurrence of string DUMMY followed with space starting from ^

Tested and written this in PERL, thought/views/improvements are most welcome here.

Thanks,
R. Singh
This User Gave Thanks to RavinderSingh13 For This Post:
nezabudka
 

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LEARN ABOUT DEBIAN

css::dom::rule

CSS::DOM::Rule(3pm)					User Contributed Perl Documentation				       CSS::DOM::Rule(3pm)

NAME

       CSS::DOM::Rule - CSS rule class for CSS::DOM

VERSION

       Version 0.14

SYNOPSIS

	 use CSS::DOM::Rule ':all'; # import constants

	 use CSS::DOM;
	 $sheet = new CSS::DOM;
	 $sheet->insertRule('bla blah blah {}');
	 $rule = $sheet->cssRules->[0];

	 $rule->type; # STYLE_RULE
	 $rule->cssText; # 'bla blah blah {}' or similar
	 $rule->cssText('p { margin: 0 }'); # replace it
	 $rule->parentStyleSheet; # $sheet

DESCRIPTION

       This module provides the CSS rule class for CSS::DOM. It implements the CSSRule and CSSUnknownRule DOM interfaces.

METHODS

   Constructor
       Only call the constructor on this class to create an 'unknown' rule. You have to call the constructor on a particular subclass to get
       another type. Normally you do not need to call this directly anyway. (See CSS::DOM's "parse" and "insertRule" methods.) But just in case
       you do want to call it, here it is:

	 new CSS::DOM::Rule $parent; # unknown rule

	 require CSS::DOM::Rule::Style
	 new CSS::DOM::Rule::Style $parent;
	 # etc.

       $parent is the parent rule, if the rule is nested, or the parent style sheet otherwise.

   Object Methods
       type
	   Returns one of the constants below indicating the type of rule.

       cssText
	   Returns this rule's CSS code. If you pass an argument, it will be parsed as the new CSS code for this rule (replacing the existing
	   data), and the old value will be returned. This method will die if the replacement CSS code creates a different type of rule.

       parentStyleSheet
	   This returns the style sheet to which the rule belongs.

       parentRule
	   This returns the rule's parent rule, if there is one, or an empty list otherwise. There is only a parent rule if this one is nested,
	   e.g., inside a media rule.

EXPORTS

       The following constants that indicate the type of rule will be exported on request (individually or with the ':all' tag):

	 UNKNOWN_RULE
	 STYLE_RULE
	 CHARSET_RULE
	 IMPORT_RULE
	 MEDIA_RULE
	 FONT_FACE_RULE
	 PAGE_RULE

SEE ALSO

       CSS::DOM

       CSS::DOM::Rule::Style

       CSS::DOM::Rule::Media

       CSS::DOM::Rule::Page

       CSS::DOM::Rule::Import

perl v5.10.1							    2010-12-10						       CSS::DOM::Rule(3pm)
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