hash with an initial key/value of ' '

mikejones has asked for the wisdom of the Perl Monks concerning the following question:

I think I understand why my hash has initial values of ' ' from Dumper, because first time through there is no data...duh, but is there a better way to do what I am doing here? thank you!

my %hash ;
my ($remote_mt,$local_mnt);

while (<DATA>) {
    unless ( /\A#|^$/ ) {
        ($remote_mt,$local_mt) = +(split)[0,1] if (/nfs/i);
        $hash {$remote_mt} = $local_mt;
    }
}
if ( %hash ) {
    while ( my ($k, $v) = each(%hash) ) {
        print "\nKicking my dog off my leg: $k => $v\n" ;
        print qx(date +%x" "%X) ;
    }
}
else {
    print "\n", qx(date +%x" "%X) ;
    die "YIKES, my dog is on my leg!\n" ;
}

use Data::Dumper;
print Dumper(\%hash);
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__OUTPUT__

$ perl foo
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### Here is what I refer to, no data initially ###
Kicking my dog off my leg: => 04/30/08 12:54:31 Kicking my dog off my leg: prdfs80:/var/opt/ha_prdfs80 => /var/opt/prd +fs80 04/30/08 12:54:31 Kicking my dog off my leg: dev0cl01:/home/admin => /home/admin 04/30/08 12:54:31 $VAR1 = { '' => undef, 'prdfs80:/var/opt/ha_prdfs80' => '/var/opt/prdfs80', 'dev0cl01:/home/admin' => '/home/admin' };
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__DATA__ # System /etc/fstab file. Static information about the file systems # See fstab(4) and sam(1M) for further details on configuring devices. /dev/vg00/lvol3 / vxfs delaylog 0 1 /dev/vg00/lvol1 /stand hfs defaults 0 1 /dev/vg00/lvol4 /home vxfs delaylog 0 2 /dev/vg00/lvol5 /opt vxfs delaylog 0 2 /dev/vg00/lvol6 /tmp vxfs delaylog 0 2 /dev/vg00/lvol7 /usr vxfs delaylog 0 2 /dev/vg00/lvol9 /var vxfs delaylog 0 2 prdfs80:/var/opt/ha_prdfs80 /var/opt/prdfs80 nfs defaults 0 0 dev0cl01:/home/admin /home/admin nfs defaults 0 2 ~
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Re: hash with an initial key/value of ' ' by pc88mxer (Vicar) on Apr 30, 2008 at 17:25 UTC
You are assigning to `$hash{$remote_mt}` even when the test `/nfs/` fails, and that case `$remote_mt` is `undef`. I think you want: `while (<DATA>) { unless ( /\A#\|^$/ ) { if (/nfs/) { ($remote_mt,$local_mt) = +(split)[0,1]; $hash{$remote_mt} = $local_mt; } } }` [download] I would probably write the loop like this: `while (<DATA>) { next if /^\s*#/; my @f = split(' ', $_); if ($f[2] eq "nfs") { $hash{$f[0]} = $f[1]; } }` [download] Just a little more robust in case some other field has 'nfs' in it.	[reply] [d/l] [select]
Re: hash with an initial key/value of ' ' by kyle (Abbot) on Apr 30, 2008 at 17:19 UTC
I think this: `($remote_mt,$local_mt) = +(split)[0,1] if (/nfs/i); $hash {$remote_mt} = $local_mt;` [download] ...should be this: `if ( /nfs/i ) { ($remote_mnt,$local_mnt) = +(split)[0,1]; $hash {$remote_mnt} = $local_mnt; }` [download] Also, you've misnamed/typoed your *_mnt variables in several places. If you'd Use strict and warnings, this would jump out.	[reply] [d/l] [select]