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Top Forums Shell Programming and Scripting Problem on understanding the regexp command Post 302745027 by Yoda on Sunday 16th of December 2012 10:41:22 AM
Old 12-16-2012
I ran this regex in PERL to show you what exactly is happening:-
Code:
#!/usr/bin/perl

my $str = 'abc/def/gh';
my @r_1 = $str =~ /(\S+)\//;
my @r_2 = $str =~ /\/(\S+)/;
print "String: ", $str, "\nRegex 1: ", @r_1, "\nRegex 2: ", @r_2, "\n";

Code:
./regex.pl
String: abc/def/gh
Regex 1: abc/def
Regex 2: def/gh

In 1st regex, the string is getting split considering last / sign.
In 2nd regex, the string is getting split considering first / sign.
So basically whatever is there before the first & last / is getting omitted. I hope you understood.
This User Gave Thanks to Yoda For This Post:
 

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textutil::trim(n)				    Text and string utilities, macro processing 				 textutil::trim(n)

__________________________________________________________________________________________________________________________________________________

NAME
textutil::trim - Procedures to trim strings SYNOPSIS
package require Tcl 8.2 package require textutil::trim ?0.7? ::textutil::trim::trim string ?regexp? ::textutil::trim::trimleft string ?regexp? ::textutil::trim::trimright string ?regexp? ::textutil::trim::trimPrefix string prefix ::textutil::trim::trimEmptyHeading string _________________________________________________________________ DESCRIPTION
The package textutil::trim provides commands that trim strings using arbitrary regular expressions. The complete set of procedures is described below. ::textutil::trim::trim string ?regexp? Remove in string any leading and trailing substring according to the regular expression regexp and return the result as a new string. This is done for all lines in the string, that is any substring between 2 newline chars, or between the beginning of the string and a newline, or between a newline and the end of the string, or, if the string contain no newline, between the beginning and the end of the string. The regular expression regexp defaults to "[ \t]+". ::textutil::trim::trimleft string ?regexp? Remove in string any leading substring according to the regular expression regexp and return the result as a new string. This apply on any line in the string, that is any substring between 2 newline chars, or between the beginning of the string and a newline, or between a newline and the end of the string, or, if the string contain no newline, between the beginning and the end of the string. The regular expression regexp defaults to "[ \t]+". ::textutil::trim::trimright string ?regexp? Remove in string any trailing substring according to the regular expression regexp and return the result as a new string. This apply on any line in the string, that is any substring between 2 newline chars, or between the beginning of the string and a newline, or between a newline and the end of the string, or, if the string contain no newline, between the beginning and the end of the string. The regular expression regexp defaults to "[ \t]+". ::textutil::trim::trimPrefix string prefix Removes the prefix from the beginning of string and returns the result. The string is left unchanged if it doesn't have prefix at its beginning. ::textutil::trim::trimEmptyHeading string Looks for empty lines (including lines consisting of only whitespace) at the beginning of the string and removes it. The modified string is returned as the result of the command. BUGS, IDEAS, FEEDBACK This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category textutil of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation. SEE ALSO
regexp(n), split(n), string(n) KEYWORDS
prefix, regular expression, string, trimming CATEGORY
Text processing textutil 0.7 textutil::trim(n)
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