Re^3: Merging files

I think you should keep track of which filehandle is still open, and read it only in that case. And I am always wary of while(1) loops. But its probably just me ;--)

#!/usr/bin/perl -w
use strict;

use Fatal qw(open close);

my @files= @ARGV;

my %fh; # file => file handle
foreach my $file (@files)
  { open( my $fh, '<', $file);
    $fh{$file}= $fh;
  }

while( keys %fh)
  { foreach my $file (@files)
      { if( exists $fh{$file})
          { my $fh= $fh{$file};
            if( defined( my $line= <$fh>))
              { chomp $line; print $line;} # regular line
            else
              { delete $fh{$file};       } # eof reached for this file
          }
      }
    print "\n"; # end of line for all files
  }
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Comment on Re^3: Merging files Download Code

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Re^4: Merging files by sk (Curate) on Apr 11, 2005 at 09:23 UTC
Thanks again! Now i understand the undef issue. Also thanks for the one-liner, showed me how to use Dumper!!! Mirod, I agree, it is definitely better to keep track of filehandles and close them when they run of out data! Learnt a few nice things today :)	[reply]
Re^4: Merging files by cazz (Pilgrim) on Apr 11, 2005 at 14:26 UTC
I agree, while(1) loops can be bad. I'm fond of doing something similar to what you are doing instead of while(1). I have spent much more time than I care to remember debugging code that was due to poor while(1) implementations. I have a few minor nits to pick with your example. You don't close any of your file handles. Why keep em around once you are done? I would inject a close right before your delete Intead of repeatedly checking every file in the list you are processing, why not just check the list of files currently open? The foreach my $file (@files) loop is easy to swap out with a foreach my $fh (keys %fh) The change would look something like this: `while (keys %fh) { foreach my $fh (keys %fh) { if (defined(my $line = <$fh>)) { chomp $line; print $line; } else { close($fh); delete($fh{$fh}); } } }` [download]	[reply] [d/l]