tar.pm

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C<IO::Zlib> filehandle instead.

The remaining arguments list the files to be included in the tar file.
These files must all exist. Any files which don't exist or can't be
read are silently ignored.

If the archive creation fails for any reason, C<create_archive> will
return false. Please use the C<error> method to find the cause of the
failure.

Note that this method does not write C<on the fly> as it were; it
still reads all the files into memory before writing out the archive.
Consult the FAQ below if this is a problem.

=cut

sub create_archive {
    my $class = shift;

    my $file    = shift; return unless defined $file;
    my $gzip    = shift || 0;
    my @files   = @_;

    unless( @files ) {
        return $class->_error( qq[Cowardly refusing to create empty archive!] );
    }

    my $tar = $class->new;
    $tar->add_files( @files );
    return $tar->write( $file, $gzip );
}

=head2 Archive::Tar->list_archive ($file, $compressed, [\@properties])

Returns a list of the names of all the files in the archive.  The
first argument can either be the name of the tar file to list or a
reference to an open file handle (e.g. a GLOB reference).

If C<list_archive()> is passed an array reference as its third
argument it returns a list of hash references containing the requested
properties of each file.  The following list of properties is
supported: full_path, name, size, mtime (last modified date), mode, 
uid, gid, linkname, uname, gname, devmajor, devminor, prefix.

See C<Archive::Tar::File> for details about supported properties.

Passing an array reference containing only one element, 'name', is
special cased to return a list of names rather than a list of hash
references.

=cut

sub list_archive {
    my $class   = shift;
    my $file    = shift; return unless defined $file;
    my $gzip    = shift || 0;

    my $tar = $class->new($file, $gzip);
    return unless $tar;

    return $tar->list_files( @_ );
}

=head2 Archive::Tar->extract_archive ($file, $gzip)

Extracts the contents of the tar file.  The first argument can either
be the name of the tar file to create or a reference to an open file
handle (e.g. a GLOB reference).  All relative paths in the tar file will
be created underneath the current working directory.

C<extract_archive> will return a list of files it extracted.
If the archive extraction fails for any reason, C<extract_archive>
will return false.  Please use the C<error> method to find the cause
of the failure.

=cut

sub extract_archive {
    my $class   = shift;
    my $file    = shift; return unless defined $file;
    my $gzip    = shift || 0;

    my $tar = $class->new( ) or return;

    return $tar->read( $file, $gzip, { extract => 1 } );
}

=head2 Archive::Tar->can_handle_compressed_files

A simple checking routine, which will return true if C<Archive::Tar>
is able to uncompress compressed archives on the fly with C<IO::Zlib>,
or false if C<IO::Zlib> is not installed.

You can use this as a shortcut to determine whether C<Archive::Tar>
will do what you think before passing compressed archives to its
C<read> method.

=cut

sub can_handle_compressed_files { return ZLIB ? 1 : 0 }

sub no_string_support {
    croak("You have to install IO::String to support writing archives to strings");
}

1;

__END__

=head1 GLOBAL VARIABLES

=head2 $Archive::Tar::FOLLOW_SYMLINK

Set this variable to C<1> to make C<Archive::Tar> effectively make a
copy of the file when extracting. Default is C<0>, which
means the symlink stays intact. Of course, you will have to pack the
file linked to as well.

This option is checked when you write out the tarfile using C<write>
or C<create_archive>.

This works just like C</bin/tar>'s C<-h> option.

=head2 $Archive::Tar::CHOWN

By default, C<Archive::Tar> will try to C<chown> your files if it is
able to. In some cases, this may not be desired. In that case, set
this variable to C<0> to disable C<chown>-ing, even if it were
possible.

The default is C<1>.

=head2 $Archive::Tar::CHMOD

By default, C<Archive::Tar> will try to C<chmod> your files to
whatever mode was specified for the particular file in the archive.
In some cases, this may not be desired. In that case, set this
variable to C<0> to disable C<chmod>-ing.

The default is C<1>.

=head2 $Archive::Tar::DO_NOT_USE_PREFIX

By default, C<Archive::Tar> will try to put paths that are over 
100 characters in the C<prefix> field of your tar header, as
defined per POSIX-standard. However, some (older) tar programs 
do not implement this spec. To retain compatibility with these older 
or non-POSIX compliant versions, you can set the C<$DO_NOT_USE_PREFIX> 
variable to a true value, and C<Archive::Tar> will use an alternate 
way of dealing with paths over 100 characters by using the 
C<GNU Extended Header> feature.

Note that clients who do not support the C<GNU Extended Header>
feature will not be able to read these archives. Such clients include
tars on C<Solaris>, C<Irix> and C<AIX>.

The default is C<0>.

=head2 $Archive::Tar::DEBUG

Set this variable to C<1> to always get the C<Carp::longmess> output
of the warnings, instead of the regular C<carp>. This is the same
message you would get by doing:

    $tar->error(1);

Defaults to C<0>.

=head2 $Archive::Tar::WARN

Set this variable to C<0> if you do not want any warnings printed.
Personally I recommend against doing this, but people asked for the
option. Also, be advised that this is of course not threadsafe.

Defaults to C<1>.

=head2 $Archive::Tar::error

Holds the last reported error. Kept for historical reasons, but its
use is very much discouraged. Use the C<error()> method instead:

    warn $tar->error unless $tar->extract;

=head2 $Archive::Tar::INSECURE_EXTRACT_MODE

This variable indicates whether C<Archive::Tar> should allow
files to be extracted outside their current working directory.

Allowing this could have security implications, as a malicious
tar archive could alter or replace any file the extracting user
has permissions to. Therefor, the default is to not allow 
insecure extractions. 

If you trust the archive, or have other reasons to allow the 
archive to write files outside your current working directory, 
set this variable to C<true>.

Note that this is a backwards incompatible change from version
C<1.36> and before.

=head2 $Archive::Tar::HAS_PERLIO

This variable holds a boolean indicating if we currently have 
C<perlio> support loaded. This will be enabled for any perl
greater than C<5.8> compiled with C<perlio>. 

If you feel strongly about disabling it, set this variable to
C<false>. Note that you will then need C<IO::String> installed
to support writing stringified archives.

Don't change this variable unless you B<really> know what you're
doing.

=head2 $Archive::Tar::HAS_IO_STRING

This variable holds a boolean indicating if we currently have 
C<IO::String> support loaded. This will be enabled for any perl
that has a loadable C<IO::String> module.

If you feel strongly about disabling it, set this variable to
C<false>. Note that you will then need C<perlio> support from
your perl to be able to  write stringified archives.

Don't change this variable unless you B<really> know what you're
doing.

=head1 FAQ

=over 4

=item What's the minimum perl version required to run Archive::Tar?

You will need perl version 5.005_03 or newer.

=item Isn't Archive::Tar slow?

Yes it is. It's pure perl, so it's a lot slower then your C</bin/tar>
However, it's very portable. If speed is an issue, consider using
C</bin/tar> instead.

=item Isn't Archive::Tar heavier on memory than /bin/tar?

Yes it is, see previous answer. Since C<Compress::Zlib> and therefore
C<IO::Zlib> doesn't support C<seek> on their filehandles, there is little
choice but to read the archive into memory.
This is ok if you want to do in-memory manipulation of the archive.
If you just want to extract, use the C<extract_archive> class method
instead. It will optimize and write to disk immediately.

=item Can't you lazy-load data instead?

No, not easily. See previous question.

=item How much memory will an X kb tar file need?

Probably more than X kb, since it will all be read into memory. If
this is a problem, and you don't need to do in memory manipulation
of the archive, consider using C</bin/tar> instead.

=item What do you do with unsupported filetypes in an archive?

C<Unix> has a few filetypes that aren't supported on other platforms,
like C<Win32>. If we encounter a C<hardlink> or C<symlink> we'll just
try to make a copy of the original file, rather than throwing an error.

This does require you to read the entire archive in to memory first,
since otherwise we wouldn't know what data to fill the copy with.
(This means that you cannot use the class methods on archives that
have incompatible filetypes and still expect things to work).

For other filetypes, like C<chardevs> and C<blockdevs> we'll warn that
the extraction of this particular item didn't work.

=item I'm using WinZip, or some other non-POSIX client, and files are not being extracted properly!

By default, C<Archive::Tar> is in a completely POSIX-compatible
mode, which uses the POSIX-specification of C<tar> to store files.
For paths greather than 100 characters, this is done using the
C<POSIX header prefix>. Non-POSIX-compatible clients may not support
this part of the specification, and may only support the C<GNU Extended
Header> functionality. To facilitate those clients, you can set the
C<$Archive::Tar::DO_NOT_USE_PREFIX> variable to C<true>. See the 
C<GLOBAL VARIABLES> section for details on this variable.

Note that GNU tar earlier than version 1.14 does not cope well with
the C<POSIX header prefix>. If you use such a version, consider setting
the C<$Archive::Tar::DO_NOT_USE_PREFIX> variable to C<true>.

=item How do I extract only files that have property X from an archive?

Sometimes, you might not wish to extract a complete archive, just
the files that are relevant to you, based on some criteria.

You can do this by filtering a list of C<Archive::Tar::File> objects
based on your criteria. For example, to extract only files that have
the string C<foo> in their title, you would use:

    $tar->extract( 
        grep { $_->full_path =~ /foo/ } $tar->get_files
    ); 

This way, you can filter on any attribute of the files in the archive.
Consult the C<Archive::Tar::File> documentation on how to use these
objects.

=item How do I access .tar.Z files?

The C<Archive::Tar> module can optionally use C<Compress::Zlib> (via
the C<IO::Zlib> module) to access tar files that have been compressed
with C<gzip>. Unfortunately tar files compressed with the Unix C<compress>
utility cannot be read by C<Compress::Zlib> and so cannot be directly
accesses by C<Archive::Tar>.

If the C<uncompress> or C<gunzip> programs are available, you can use
one of these workarounds to read C<.tar.Z> files from C<Archive::Tar>

Firstly with C<uncompress>

    use Archive::Tar;

    open F, "uncompress -c $filename |";
    my $tar = Archive::Tar->new(*F);
    ...

and this with C<gunzip>

    use Archive::Tar;

    open F, "gunzip -c $filename |";
    my $tar = Archive::Tar->new(*F);
    ...

Similarly, if the C<compress> program is available, you can use this to
write a C<.tar.Z> file

    use Archive::Tar;
    use IO::File;

    my $fh = new IO::File "| compress -c >$filename";
    my $tar = Archive::Tar->new();
    ...
    $tar->write($fh);
    $fh->close ;

=item How do I handle Unicode strings?

C<Archive::Tar> uses byte semantics for any files it reads from or writes
to disk. This is not a problem if you only deal with files and never
look at their content or work solely with byte strings. But if you use
Unicode strings with character semantics, some additional steps need
to be taken.

For example, if you add a Unicode string like

    # Problem
    $tar->add_data('file.txt', "Euro: \x{20AC}");

then there will be a problem later when the tarfile gets written out
to disk via C<$tar->write()>:

    Wide character in print at .../Archive/Tar.pm line 1014.

The data was added as a Unicode string and when writing it out to disk,
the C<:utf8> line discipline wasn't set by C<Archive::Tar>, so Perl
tried to convert the string to ISO-8859 and failed. The written file
now contains garbage.

For this reason, Unicode strings need to be converted to UTF-8-encoded
bytestrings before they are handed off to C<add_data()>:

    use Encode;
    my $data = "Accented character: \x{20AC}";
    $data = encode('utf8', $data);

    $tar->add_data('file.txt', $data);

A opposite problem occurs if you extract a UTF8-encoded file from a 
tarball. Using C<get_content()> on the C<Archive::Tar::File> object
will return its content as a bytestring, not as a Unicode string.

If you want it to be a Unicode string (because you want character
semantics with operations like regular expression matching), you need
to decode the UTF8-encoded content and have Perl convert it into 
a Unicode string:

    use Encode;
    my $data = $tar->get_content();
    
    # Make it a Unicode string
    $data = decode('utf8', $data);

There is no easy way to provide this functionality in C<Archive::Tar>, 
because a tarball can contain many files, and each of which could be
encoded in a different way.

=back

=head1 TODO

=over 4

=item Check if passed in handles are open for read/write

Currently I don't know of any portable pure perl way to do this.
Suggestions welcome.

=item Allow archives to be passed in as string

Currently, we only allow opened filehandles or filenames, but
not strings. The internals would need some reworking to facilitate
stringified archives.

=item Facilitate processing an opened filehandle of a compressed archive

Currently, we only support this if the filehandle is an IO::Zlib object.
Environments, like apache, will present you with an opened filehandle
to an uploaded file, which might be a compressed archive.

=back

=head1 SEE ALSO

=over 4

=item The GNU tar specification

C<http://www.gnu.org/software/tar/manual/tar.html>

=item The PAX format specication

The specifcation which tar derives from; C< http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html>

=item A comparison of GNU and POSIX tar standards; C<http://www.delorie.com/gnu/docs/tar/tar_114.html>

=item GNU tar intends to switch to POSIX compatibility

GNU Tar authors have expressed their intention to become completely
POSIX-compatible; C<http://www.gnu.org/software/tar/manual/html_node/Formats.html>

=item A Comparison between various tar implementations

Lists known issues and incompatibilities; C<http://gd.tuwien.ac.at/utils/archivers/star/README.otherbugs>

=back

=head1 AUTHOR

This module by Jos Boumans E<lt>[e-mail]<gt>.

Please reports bugs to E<lt>[e-mail]<gt>.

=head1 ACKNOWLEDGEMENTS

Thanks to Sean Burke, Chris Nandor, Chip Salzenberg, Tim Heaney and
especially Andrew Savige for their help and suggestions.

=head1 COPYRIGHT

This module is copyright (c) 2002 - 2007 Jos Boumans 
E<lt>[e-mail]<gt>. All rights reserved.

This library is free software; you may redistribute and/or modify 
it under the same terms as Perl itself.

=cut