CODEWITHSUNDEEP
perlftpgzipperl-io
kjo
kjo

Reputation: 35321

FTP + uncompress + readline

I want to extract some data from a large-ish (3+ GB, gzipped) FTP download, and do this on-the-fly, to avoid dumping then full download on my disk.

To extract the desired data I need to examine the uncompressed stream line-by-line.

So I'm looking for the moral equivalent of

use PerlIO::gzip;

my $handle = open '<:gzip', 'ftp://ftp.foobar.com/path/to/blotto.txt.gz'
             or die $!;
for my $line (<$handle>) {
    # etc.
}
close($handle);

FWIW: I know how to open a read handle to ftp://ftp.foobar.com/path/to/blotto.txt.gz (with Net::FTP::repr), but I have not yet figured out how to add a :gzip layer to this open handle.

It took me a lot longer than it should have to find the answer to the question above, so I thought I'd post it for the next person who needs it.

Upvotes: 0

Views: 122

Answers (2)

pmqs
pmqs

Reputation: 3705

The code below is from IO::Compress FAQ

use Net::FTP;
use IO::Uncompress::Gunzip qw(:all);

my $ftp = new Net::FTP ...

my $retr_fh = $ftp->retr($compressed_filename);
gunzip $retr_fh => $outFilename, AutoClose => 1
    or die "Cannot uncompress '$compressed_file': $GunzipError\n";

To get the data line by line, change it to this

use Net::FTP;
use IO::Uncompress::Gunzip qw(:all);

my $ftp = new Net::FTP ...

my $retr_fh = $ftp->retr($compressed_filename);
my $gunzip = new IO::Uncompress::Gunzip $retr_fh, AutoClose => 1
    or die "Cannot uncompress '$compressed_file': $GunzipError\n";

while(<$gunzip>)
{
    ...
}

Upvotes: 1

kjo
kjo

Reputation: 35321

OK, the answer is (IMO) not at all obvious: binmode($handle, ':gzip').

Here's a fleshed-out example:

use strict;
use Net::FTP;
use PerlIO::gzip;

my $ftp = Net::FTP->new('ftp.foobar.com') or die $@;
$ftp->login or die $ftp->message;  # anonymous FTP
my $handle = $ftp->retr('/path/to/blotto.txt.gz') or die $ftp->message;

binmode($handle, ':gzip');

for my $line (<$handle>) {
    # etc.
}
close($handle);

Upvotes: 1

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