The scalar context range operator (flip flop) can be powerful fu:

use strict;
use warnings;

my $match = 'lvol[35]';

while (<DATA>) {
    next if ! (my $it = /^LV Name/ .. /^LV Name/ && ! /$match/);
    
    if ($it =~ /E0/) {
        print "---\n";
        next;
    }
    
    print "$it: $_";
}

__DATA__
--- Logical volumes ---
LV Name                     /dev/vg00/lvol3
VG Name                     /dev/vg00
Various stuff omitted
LV Name                     /dev/vg00/lvol4
VG Name                     /dev/vg00
Various stuff omitted
LV Name                     /dev/vg00/lvol5
VG Name                     /dev/vg00
Various stuff omitted
LV Name                     /dev/vg00/lvol6
VG Name                     /dev/vg00
Various stuff omitted
[download]

Prints:

1: LV Name                     /dev/vg00/lvol3
2: VG Name                     /dev/vg00
3: Various stuff omitted
---
1: LV Name                     /dev/vg00/lvol5
2: VG Name                     /dev/vg00
3: Various stuff omitted
---
[download]

If you are unfamiliar with it take a look at Flipin good, or a total flop?.

Hi everybody, I'm just a perl newbie that entered through these monastery gates not so many weeks ago...I was wondering if I could add some extra functionality and fixes to the module Linux::LVM instead of forking it, as many people do with many modules around.

I believe I'm able to work on the module itself with the creator's permission, or to do it in some other way.

What shall I do? Any comments, help and guidelines would be very appreciated, fellow brothers. On the meantime, I'll try to contact the module creator.

Thank you!

(let my faith in Perl Best Practices, Perl::Critic and nice coding guidelines enlighten my path...)

I think I misplaced this post. I will try to do it in the correct way then...you will find the correct post there: Right ways to get things done: improving Linux::LVM

.

[Update: GrandFather beat me to it.]

This might be a good place to make use of the flip-flop operator. It can help you avoid the ugly $start / $end / $started variables to keep track of where you are:

use strict;
use warnings;

while (<DATA>){

    # Returns true after matching "LV Name",
    # and returns false after
    # matching "--- Logical extents ---".
    if (/^LV Name/ .. /--- Logical extents ---/){
        print "$_";
    }


}

__DATA__
Line above
--- Logical volumes ---
LV Name                     /dev/vg00/lvol3
VG Name                     /dev/vg00
LV Permission               read/write
...
   --- Logical extents ---
Line below
[download]

LV Name                     /dev/vg00/lvol3
VG Name                     /dev/vg00
LV Permission               read/write
...
   --- Logical extents ---
[download]

my $started = 0;
open(LVMINFO, '<', $filename);
while (<LVMINFO>) {
  $started = 1 if /^LV Name/;
  next unless $started;
  last if /--- Logical extents ---/;
  chomp;
  # Process
  # Process
  # Process
}
close(LVMINFO);
[download]

Alternately, you can play with the input record separator to get the chunks you need.

use strict;
use warnings;
use Data::Dumper;

my @filesys;

{
  local $/ = '--- Logical extents ---';
  while ( my $record = <DATA>) {
      chomp $record;
      next unless $record =~ /--- Logical volumes ---/;
      $record =~ s/^.*--- Logical volumes ---\n//s;
      my ($beginning, $end) = split /--- Distribution of logical volum
+e ---/, $record;
      my %params = split /  +|\n/, $beginning;
      my @lines = split /\n/, $end;
      for my $line(@lines) {
          next if $line =~ /PV Name/;
          next if $line !~ /\S/;
          my ($name, $le, $pe) = split ' ', $line;
          push @{$params{PV}}, {'Name', $name, 'LE on PV', $le, 'PE on
+ PV', $pe};
      }
      push @filesys, \%params;
  }
}

print Dumper \@filesys;



__DATA__
<---snipp--->
--- Logical volumes ---
LV Name                     /dev/vg00/lvol3
VG Name                     /dev/vg00
LV Permission               read/write
LV Status                   available/syncd
Mirror copies               1
Consistency Recovery        MWC
Schedule                    parallel
LV Size (Mbytes)            300
Current LE                  75
Allocated PE                150
Stripes                     0
Stripe Size (Kbytes)        0
Bad block                   off
Allocation                  strict/contiguous
IO Timeout (Seconds)        default

   --- Distribution of logical volume ---
   PV Name            LE on PV  PE on PV
   /dev/dsk/c3t6d0    75        75
   /dev/dsk/c38t6d0   75        75

   --- Logical extents ---
Some other bogus crap that 
needs to be ignored.
--- Logical volumes ---
LV Name                     /dev/vg00/lvol33
VG Name                     /dev/vg003
LV Permission               read/write
LV Status                   available/syncd
Mirror copies               1
Consistency Recovery        MWC
Schedule                    parallel
LV Size (Mbytes)            500
Current LE                  70
Allocated PE                150
Stripes                     0
Stripe Size (Kbytes)        0
Bad block                   off
Allocation                  strict/contiguous
IO Timeout (Seconds)        default

   --- Distribution of logical volume ---
   PV Name            LE on PV  PE on PV
   /dev/dsk/c3t6d03   75        75
   /dev/dsk/c38t6d03  75        75

   --- Logical extents ---
<---snip--->
[download]

sub Get_Sect  {
   my $targetLV = shift;
   my $section='';
   my ($name,$value);
   my %data;
         
   open my $IN,  '<', 'testpars.dat';
   LINE:
   while (<$IN>) {
      chomp;
      if (/^\s*$/) {
         return \%data     if ($data{'LV_Name'} = $targetLV);
         $section = '';
         next LINE;
      }
      if (/^--- Logical volumes ---/) {
         $section = 'vol';
         next LINE;
      }
      if ($section eq 'vol') {
         ($name,$value) = unpack('a28 a*',$_);
         $name =~ s/(\s+\(.+\))?\s+$//; #remove paren & spaces at end
         $name =~ s/\s/_/g;   
         $data{$name} = $value;
      }
   }
}
[download]