#!/usr/bin/perl
use strict;
use warnings;

my @headers = qw(name size used free capacity mount);
my @df = &readDFfile('test.dat');
shift @df;  # get rid of the header

my %devices;
for my $line (@df) {
    my %info;
    @info{@headers} = split /\s+/, $line;  # note the hash slice
    $info{capacity} = _percentage_to_decimal($info{capacity});
    $devices{ $info{mount} } = \%info;
}

# Change 12.3% to .123
sub _percentage_to_decimal {
    my $percentage = shift;
    $percentage =~ s{%}{};
    return $percentage / 100;
}
# Now the information for each device is in a hash of hashes.

# Show how much space is free in device /dev/ad4s1e
print $devices{"/production/log"}{free} ;
print "\n";
for my $info (values %devices) {
    # Skip to the next device if its capacity is not over 60%.
    next unless $info->{capacity} > .10;

    # Print some info about each device
    printf "%s is at %d%% with %dK remaining.\n",
        $info->{mount}, $info->{capacity}*100, $info->{free};
}

exit;

sub readDFfile
{
     my ($rdofnm, @arglst) = @_;
     if (!defined $rdofnm) { $rdofnm = ''; }

     # -----[ Was command, now reading from file for testing purposes ]--------------
     # my @df = `df -k`;
     # ------------------------------------------------------------------------------
     my @df = ();
     if (open RDOFIL, '<', $rdofnm)
     {
          @df = <RDOFIL>;
          close RDOFIL;
     }
     # ------------------------------------------------------------------------------

     return @df;
}

__END__

C:\Steve\Dev\PerlMonks\P-2013-12-18@1604-Hash-Undef>perl -v

This is perl 5, version 16, subversion 3 (v5.16.3) built for MSWin32-x64-multi-thread
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2012, Larry Wall

Binary build 1603 [296746] provided by ActiveState http://www.ActiveState.com
Built Mar 13 2013 13:31:10

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl".  If you have access to the
Internet, point your browser at http://www.perl.org/, the Perl Home Page.

C:\Steve\Dev\PerlMonks\P-2013-12-18@1604-Hash-Undef>type test.dat
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      28313732   9816924  17035356  37% /
/dev/sda1               101086     27516     68351  29% /boot
tmpfs                  2987896         0   2987896   0% /dev/shm
/dev/mapper/VolGroupPROD-ExportHome
                      15481840   3495504  11199904  24% /export/home
/dev/mapper/VolGroupPROD-Production
                      15481840   1523692  13171716  11% /production
/dev/mapper/VolGroupPROD-ProdLog
                      30963708  20410952   8979892  70% /production/log
/dev/mapper/VolGroupPROD-ProdArchive
                      10313016   1693640   8095500  18% /production/archive

C:\Steve\Dev\PerlMonks\P-2013-12-18@1604-Hash-Undef>perl testdf2.pl
Use of uninitialized value $percentage in substitution (s///) at testdf2.pl line 20.
Use of uninitialized value $percentage in division (/) at testdf2.pl line 21.
Use of uninitialized value $info{"mount"} in hash element at testdf2.pl line 14.
Use of uninitialized value $percentage in substitution (s///) at testdf2.pl line 20.
Use of uninitialized value $percentage in division (/) at testdf2.pl line 21.
Use of uninitialized value $info{"mount"} in hash element at testdf2.pl line 14.
Use of uninitialized value $percentage in substitution (s///) at testdf2.pl line 20.
Use of uninitialized value $percentage in division (/) at testdf2.pl line 21.
Use of uninitialized value $info{"mount"} in hash element at testdf2.pl line 14.
Use of uninitialized value $percentage in substitution (s///) at testdf2.pl line 20.
Use of uninitialized value $percentage in division (/) at testdf2.pl line 21.
Use of uninitialized value $info{"mount"} in hash element at testdf2.pl line 14.
Use of uninitialized value $percentage in substitution (s///) at testdf2.pl line 20.
Use of uninitialized value $percentage in division (/) at testdf2.pl line 21.
Use of uninitialized value $info{"mount"} in hash element at testdf2.pl line 14.
8979892
/production/log is at 70% with 8979892K remaining.
/ is at 37% with 17035356K remaining.
/boot is at 28% with 68351K remaining.
/export/home is at 24% with 11199904K remaining.
/production is at 11% with 13171716K remaining.
/production/archive is at 18% with 8095500K remaining.