Shell Programming and Scripting

#!/usr/bin/perl

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

use warnings;
use strict;

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

my ($lines) = 0;

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

my ($string);
my ($input);
my ($winner);
my ($min) = 1.0E300;

while (<>) {
  print " Bounds on this search: $first, $last\n" unless $lines;
  $lines++;
  chomp;
  print "\n";
  print " Initial string = \"$_\"\n";
  $input = $_;
  pos $input = 0;
  $min    = 1.0E300;
  $winner = 0;

  # See Perl Best Practices, p 250 ff for details on loops like
  # this.
  while ( pos $input < length $input ) {
    if ( $input =~ m{ \G ($first.*?$last) }gcxms ) {
      $string = $1;
      print " matched string :$string:\n" if $debug;
      if ( length $string < $min ) {
        $winner = $string;
        $min    = length $winner;
      }
    }
    else {    # move pointer ahead
      $input =~ m/ \G (.) /gcxms;
    }
    print " so far, winner :$winner:, min :$min:\n" if $debug;
  }
  if ($winner) {
    print " Shortest substring = \"$winner\"\n";
  }
  else {
    print STDERR " No substring found, continuing.\n";
  }
}

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

exit(0);

% ./p1 a d data1
 Bounds on this search: a, d

 Initial string = "abcdpqracdpqaserd"
 Shortest substring = "acd"

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

 Initial string = "ad"
 Shortest substring = "ad"

 Initial string = "abcdabcadabcefdadabcd"
 Shortest substring = "ad"

 Initial string = "abc--------------------de"
 Shortest substring = "abc--------------------d"

 Initial string = "abc0123456789defgh   d"
 Shortest substring = "abc0123456789d"
 ( Lines read: 6 )

awk -v s="abcdpqracdpqaserd" -v start="a" -v end="d" 'BEGIN{
	re=start"[^"end"]*"end
	min=(length(s)+0)
		while (match(s,re)){
			all[length(substr(s,RSTART,RLENGTH))]=substr(s,RSTART,RLENGTH)
			s=substr(s,++i)
			}
	for(p in all)
		if((p+0)<min)
			{min=p;shortest=all[p]}
print shortest
}'