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

Hello,

Is is possible to use the zless utility and Perl's open function to read a gzipped file?

I tried using open and piping to zless but that did not work. Ultimately, I would like to read a gzipped file line by line with a while loop without unzipping it such as: 

open(FILE, '<', $filename) #somehow using zless or other?
while <FILE>
{
  ...do action on each line...
}

[download]

Replies are listed 'Best First'.
Re: perl OPEN function and zless
by davido (Cardinal) on Jul 14, 2011 at 21:17 UTC

    CPAN: Perl's killer app: PerlIO::via::gzip

    I don't know how robust this is, but it worked on a simple test script I just tried myself.

    use strict;
use warnings;
use autodie;

use PerlIO::via::gzip;

my $filename = 'example.txt.gz';

open my $fh, "<:via(gzip)", $filename;
while ( <$fh> ) {
    print $. . $_;
}

    [download]

    I think that's what you seem to be looking for. You could always just open a pipe from the shell instead though.


    Dave

[reply]
[d/l]
      Thanks, I will look at that but I have used the pipe function from the shell instead for now
[reply]
Re: perl OPEN function and zless
by betterworld (Curate) on Jul 14, 2011 at 21:02 UTC

    Why would you want to read from zless? It's a pager, which is designed to scroll through a gzipped file (on a terminal). Better choices are 'gunzip' or 'zcat' (maybe look at the man pages).

    To use these tools with "open", you need to use "-|" rather than "<". perldoc -f open will tell you more about it.

    Searching CPAN for gzip might also help. IO::Uncompress::Gunzip is installed with perl by default.

[reply]
      Thanks,
      I used this to get it to work: 
      open(FILE, '-|', "gunzip -c $filename");

while (FILE) 
{
..do action..
}

      [download]
[reply]
[d/l]

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