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Top Forums Shell Programming and Scripting shell script for extracting out the shortest substring from the given starting and en Post 302141524 by drl on Friday 19th of October 2007 12:59:21 PM
Old 10-19-2007
Hi.

I like the solution from aigles. I don't see one yet on perl.

The perl RE syntax has special features for the shortest match. Here is the entire code, along with diagnostic code, minimal argument processing, etc:
Code:
#!/usr/bin/perl

# @(#) p1       Demonstrate non-greedy matching perl RE syntax.

use warnings;
use strict;

my ($debug);
$debug = 0;
$debug = 1;

my ($lines) = 0;

my ($usage) = "usage: $0 first last\n";
my ($first) = shift || die "$usage";
my ($last)  = shift || die "$usage";

my ($string);

while (<>) {
  print " Bounds on this search: $first, $last\n" unless $lines;
  $lines++;
  chomp;
  print "\n";
  print " Initial string = \"$_\"\n";
  if (/($first.*?$last)/) {
    $string = $1;
    print " Shortest substring = \"$string\"\n";
  }
  else {
    print STDERR " No substring found, continuing.\n";
  }
}

print STDERR " ( Lines read: $lines )\n";

exit(0);

Running this on your test line and a few others in file data1:
Code:
% ./p1 a d data1
 Bounds on this search: a, d

 Initial string = "abcdpqracdpqaserd"
 Shortest substring = "abcd"

 Initial string = "abc"
 No substring found, continuing.

 Initial string = "abcdddd"
 Shortest substring = "abcd"
 ( Lines read: 3 )

The heart of the match is in these characters .*?

See the man pages for:
Code:
perlre              Perl regular expressions, the rest of the story
perlreref           Perl regular expressions quick reference

for details ... cheers, drl
 

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textutil::trim(3tcl)				    Text and string utilities, macro processing 			      textutil::trim(3tcl)

__________________________________________________________________________________________________________________________________________________

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(3tcl), split(3tcl), string(3tcl) KEYWORDS
prefix, regular expression, string, trimming CATEGORY
Text processing textutil 0.7 textutil::trim(3tcl)
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