Re: Leading Spaces and split()

[Bill Luebkert]

On 8/19/2011 1:01 PM, Rothenmaier, Deane C. wrote:
> Greetings, O Wise Ones…
>
> I’m trying to understand the behavior I’m getting from this code:
...
> The red text illustrates the error (if such it be?). My SWAG is that the 
> “nothing” between Perl’s ‘^’ anchor and the first space in $string2 is what’s 
> causing the problem. Can someone confirm this? Or provide me with the correct 
> answer if I’m wrong?

perlfunc under split:
             As a special case, specifying a PATTERN of space (' ') will split 
on
             white space just as "split" with no arguments does. Thus,
             "split(' ')" can be used to emulate awk's default behavior, whereas
             "split(/ /)" will give you as many null initial fields as there are
             leading spaces. A "split" on "/\s+/" is like a "split(' ')" except
             that any leading whitespace produces a null first field. A "split"
             with no arguments really does a "split(' ', $_)" internally.

# My version:

use strict;
use warnings;
my $string1 =
   'Windows XP Professional Service Pack 2 (build 2600) Hewlett-Packard';

my @ary1 = split ' ', $string1;
my ($win_type1, $win_ver1, $svc_pack1, $win_build1);
$win_type1 = $ary1[1];
$win_ver1 = $ary1[2];
if ($win_type1 =~ /XP/) {
        $svc_pack1 = $ary1[5];
        ($win_build1 = $ary1[7]) =~ s/\)//;
}

print "Current Method...\n";
print "Type: '$win_type1', Version: "$win_ver1',\n";
print "Service Pack: '$svc_pack1', Build: '$win_build1'\n\n";

if ($string1 =~ /XP/) {
        my ($win_type2, $win_ver2, $svc_pack2, $win_build2) =
          (split /\s+/, $string1)[1, 2, 5, 7];
        $win_build2 =~ s/\)//;
        print "Proposed Method...\n";
        print "Type: '$win_type2', Version: '$win_ver2',\n";
        print "Service Pack: '$svc_pack2', Build: '$win_build2'\n";
}

@ary1 = split ' ', $string1;
$win_type1 = $ary1[1];
$win_ver1 = $ary1[2];
if ($win_type1 =~ /XP/) {
        $svc_pack1 = $ary1[5];
        ($win_build1 = $ary1[7]) =~ s{\)}{};
}

print "\nFILE string:\n";
print "Current Method...\n";
print "Type: '$win_type1', Version: '$win_ver1',\n";
print "Service Pack: '$svc_pack1', Build: '$win_build1'\n\n";

my $string2 =
   "      Windows XP Professional Service Pack 2 (build 2600) Hewlett-Packard ";

if ($string2 =~ /XP/) {
        $string2 =~ s/^\s*//;   # I would either use ' ' split or add this line
        my ($win_type2, $win_ver2, $svc_pack2, $win_build2) =
          (split /\s+/, $string2)[1, 2, 5, 7];
        $win_build2 =~ s/\)//;
        print "Proposed Method...\n";
        print "Type: '$win_type2', Version: '$win_ver2',\n";
        print "Service Pack: '$svc_pack2', Build: '$win_build2'\n";
}

__END__

Current Method...
Type: 'XP', Version: 'Professional',
Service Pack: '2', Build: '2600'

Proposed Method...
Type: 'XP', Version: 'Professional',
Service Pack: '2', Build: '2600'

FILE string:
Current Method...
Type: 'XP', Version: 'Professional',
Service Pack: '2', Build: '2600'

Proposed Method...
Type: 'XP', Version: 'Professional',
Service Pack: '2', Build: '2600'
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