perlquestion
Monk::Thomas
<p>(This is part of a larger program. I stripped the code example down.)</p>
<p>I'd like to get a file from somewhere (HTTP, SCP, FTP, local file) and make a local copy via fetch(), pass the file descriptor around, modify the content and later on write the file content to one or more other files.</p>
<p>Alternative a) It would be easy to do this via actual file names but I would like to use open filehandles without an actual filename. This way I wouldn't have to worry about someone tampering with my data while I'm working on it.</p>
<p>Alternative b) I don't want to slurp the file content into main memory.</p>
<p>Script output:</p>
<pre>
[FETCH] The file '/etc/services' has inode 2105201 and size 19398
[FETCH] The file 'GLOB(0x10c7c78)' has inode 142159 and size 19398
[STORE] The file 'GLOB(0x10c7c78)' has inode 142159 and size 19398
[STORE] The file '/tmp/services.d1JH' has inode 142160 and size 0
[STORE] Copying filehandle tmp1 (GLOB(0x10c7c78)) to tmp2 (/tmp/services.d1JH) file.
[STORE] The file 'GLOB(0x10c7c78)' has inode 142159 and size 19398
[STORE] The file '/tmp/services.d1JH' has inode 142160 and size 0
-rw------- 1 thomas thomas 0 Jan 16 21:15 /tmp/services_copy
</pre>
<p>As you can see, the store() function seems to receive the correct data to the file object, but copy does not actually copy the file. I seriously scratched my head on this, but so far no enlightenment has occured. Buffering issue? Copy not happy with the GLOBs? Something totally different?</p>
<p>Time to confess my non-knowledge and ask a senior monk. Hopefully I get something more then just a koan. ;)</p>
<code>
#!/usr/bin/env perl
use strict;
use warnings;
use 5.010_001;
use English qw( -no_match_vars ); # avoid regex performance penalty
use File::Copy;
use File::Temp qw(tempfile);
use Readonly;
Readonly my $STAT_INODE => '1';
Readonly my $STAT_SIZE => '7';
my $tmp_fh = fetch();
store($tmp_fh);
exit 0;
sub fetch {
my $src_file = '/etc/services';
show_filestats('FETCH', $src_file);
my ( $tmp1_fh, $tmp1_filename ) = tempfile();
unlink $tmp1_filename; #
copy $src_file, $tmp1_fh
or die "$ERRNO\n";
show_filestats('FETCH', $tmp1_fh);
return $tmp1_fh;
}
sub store {
my $tmp1_fh = shift;
my $tmp2_file = File::Temp->new( TEMPLATE => '/tmp/services.XXXX', UNLINK => 0 );
my $dst_file = '/tmp/services_copy';
show_filestats('STORE', $tmp1_fh);
show_filestats('STORE', $tmp2_file);
print "[STORE] Copying filehandle tmp1 ($tmp1_fh) to tmp2 ($tmp2_file) file.\n"
or croak();
copy $tmp1_fh, $tmp2_file
or die "E: $ERRNO\n";
show_filestats('STORE', $tmp1_fh);
show_filestats('STORE', $tmp2_file);
# apply permissions and ACLs
rename $tmp2_file, $dst_file
or die "E: $ERRNO\n";
}
sub show_filestats {
my $id = shift;
my $fh = shift;
my ( $inode, $size ) = ( stat $fh )[ $STAT_INODE, $STAT_SIZE ];
print "[$id] The file '$fh' has inode $inode and size $size\n"
or croak();
return;
}
</code>