IO::Zlib - IO:: style interface to Compress::Zlib
With any version of Perl 5 you can use the basic OO interface:
use IO::Zlib;
$fh = new IO::Zlib;
if ($fh->open("file.gz", "rb")) {
print <$fh>;
$fh->close;
}
$fh = IO::Zlib->new("file.gz", "wb9");
if (defined $fh) {
print $fh "bar\n";
$fh->close;
}
$fh = IO::Zlib->new("file.gz", "rb");
if (defined $fh) {
print <$fh>;
undef $fh; # automatically closes the file
}
With Perl 5.004 you can also use the TIEHANDLE interface to access compressed files just like ordinary files:
use IO::Zlib;
tie *FILE, 'IO::Zlib', "file.gz", "wb";
print FILE "line 1\nline2\n";
tie *FILE, 'IO::Zlib', "file.gz", "rb";
while (<FILE>) { print "LINE: ", $_ };
IO::Zlib provides an IO:: style interface to Compress::Zlib and
hence to gzip/zlib compressed files. It provides many of the same methods
as the IO::Handle interface.
Starting from IO::Zlib version 1.02, IO::Zlib can also use an
external gzip command. The default behaviour is to try to use
an external gzip if no Compress::Zlib can be loaded, unless
explicitly disabled by
use IO::Zlib qw(:gzip_external 0);
If explicitly enabled by
use IO::Zlib qw(:gzip_external 1);
then the external gzip is used instead of Compress::Zlib.
IO::Zlib object. If it receives any parameters, they are
passed to the method open; if the open fails, the object is destroyed.
Otherwise, it is returned to the caller.
open takes two arguments. The first is the name of the file to open
and the second is the open mode. The mode can be anything acceptable to
Compress::Zlib and by extension anything acceptable to zlib (that
basically means POSIX fopen() style mode strings plus an optional number
to indicate the compression level).
getpos().
Not yet supported.
If the external gzip is used, the following opens are used:
open(FH, "gzip -dc $filename |") # for read opens
open(FH, " | gzip > $filename") # for write opens
You can modify the 'commands' for example to hardwire an absolute path by e.g.
use IO::Zlib ':gzip_read_open' => '/some/where/gunzip -c %s |';
use IO::Zlib ':gzip_write_open' => '| /some/where/gzip.exe > %s';
The %s is expanded to be the filename (sprintf is used, so be
careful to escape any other % signs). The 'commands' are checked
for sanity - they must contain the %s, and the read open must end
with the pipe sign, and the write open must begin with the pipe sign.
Compress::Zlib is available. Note that this does
not mean that Compress::Zlib is being used: see /gzip_external
and gzip_used.
Compress::Zlib is
not available (see /has_Compress_Zlib), true if an external gzip
is explicitly used, false if an external gzip must not be used.
See /gzip_used.
:gzip_external, :gzip_read_open,
and :gzip_write_open. Anything else is not recognized.
:gzip_external requires one boolean argument.
:gzip_external requires one string argument.
:gzip_read_open argument must end with the pipe sign (|)
and have the %s for the filename. See /"USING THE EXTERNAL GZIP".
:gzip_external requires one string argument.
:gzip_write_open argument must begin with the pipe sign (|)
and have the %s for the filename. An output redirect (>) is also
often a good idea, depending on your operating system shell syntax.
See /"USING THE EXTERNAL GZIP".
Compress::Zlib and that the use of
an external gzip was disabled, IO::Zlib has not much chance of working.
perlfunc, perlop/"I/O Operators", IO::Handle, Compress::Zlib
Created by Tom Hughes <tom@compton.nu>.
Support for external gzip added by Jarkko Hietaniemi <jhi@iki.fi>.
Copyright (c) 1998-2004 Tom Hughes <tom@compton.nu>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.