push (@cmd, '-hda', $disks[0]) if defined $disks[0];
push (@cmd, '-hdb', $disks[1]) if defined $disks[1];
push (@cmd, '-hdc', $disks[2]) if defined $disks[2];
push (@cmd, '-hda', $disks[0]) if defined $disks[0];
push (@cmd, '-hdb', $disks[1]) if defined $disks[1];
push (@cmd, '-hdc', $disks[2]) if defined $disks[2];