archive::tar.3

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of the warnings, instead of the regular \f(CW\*(C`carp\*(C'\fR. This is the same
message you would get by doing:
.PP
.Vb 1
\&    $tar\->error(1);
.Ve
.PP
Defaults to \f(CW0\fR.
.ie n .Sh "$Archive::Tar::WARN"
.el .Sh "\f(CW$Archive::Tar::WARN\fP"
.IX Subsection "$Archive::Tar::WARN"
Set this variable to \f(CW0\fR 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.
.PP
Defaults to \f(CW1\fR.
.ie n .Sh "$Archive::Tar::error"
.el .Sh "\f(CW$Archive::Tar::error\fP"
.IX Subsection "$Archive::Tar::error"
Holds the last reported error. Kept for historical reasons, but its
use is very much discouraged. Use the \f(CW\*(C`error()\*(C'\fR method instead:
.PP
.Vb 1
\&    warn $tar\->error unless $tar\->extract;
.Ve
.ie n .Sh "$Archive::Tar::INSECURE_EXTRACT_MODE"
.el .Sh "\f(CW$Archive::Tar::INSECURE_EXTRACT_MODE\fP"
.IX Subsection "$Archive::Tar::INSECURE_EXTRACT_MODE"
This variable indicates whether \f(CW\*(C`Archive::Tar\*(C'\fR should allow
files to be extracted outside their current working directory.
.PP
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.
.PP
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 \f(CW\*(C`true\*(C'\fR.
.PP
Note that this is a backwards incompatible change from version
\&\f(CW1.36\fR and before.
.ie n .Sh "$Archive::Tar::HAS_PERLIO"
.el .Sh "\f(CW$Archive::Tar::HAS_PERLIO\fP"
.IX Subsection "$Archive::Tar::HAS_PERLIO"
This variable holds a boolean indicating if we currently have 
\&\f(CW\*(C`perlio\*(C'\fR support loaded. This will be enabled for any perl
greater than \f(CW5.8\fR compiled with \f(CW\*(C`perlio\*(C'\fR.
.PP
If you feel strongly about disabling it, set this variable to
\&\f(CW\*(C`false\*(C'\fR. Note that you will then need \f(CW\*(C`IO::String\*(C'\fR installed
to support writing stringified archives.
.PP
Don't change this variable unless you \fBreally\fR know what you're
doing.
.ie n .Sh "$Archive::Tar::HAS_IO_STRING"
.el .Sh "\f(CW$Archive::Tar::HAS_IO_STRING\fP"
.IX Subsection "$Archive::Tar::HAS_IO_STRING"
This variable holds a boolean indicating if we currently have 
\&\f(CW\*(C`IO::String\*(C'\fR support loaded. This will be enabled for any perl
that has a loadable \f(CW\*(C`IO::String\*(C'\fR module.
.PP
If you feel strongly about disabling it, set this variable to
\&\f(CW\*(C`false\*(C'\fR. Note that you will then need \f(CW\*(C`perlio\*(C'\fR support from
your perl to be able to  write stringified archives.
.PP
Don't change this variable unless you \fBreally\fR know what you're
doing.
.SH "FAQ"
.IX Header "FAQ"
.IP "What's the minimum perl version required to run Archive::Tar?" 4
.IX Item "What's the minimum perl version required to run Archive::Tar?"
You will need perl version 5.005_03 or newer.
.IP "Isn't Archive::Tar slow?" 4
.IX Item "Isn't Archive::Tar slow?"
Yes it is. It's pure perl, so it's a lot slower then your \f(CW\*(C`/bin/tar\*(C'\fR
However, it's very portable. If speed is an issue, consider using
\&\f(CW\*(C`/bin/tar\*(C'\fR instead.
.IP "Isn't Archive::Tar heavier on memory than /bin/tar?" 4
.IX Item "Isn't Archive::Tar heavier on memory than /bin/tar?"
Yes it is, see previous answer. Since \f(CW\*(C`Compress::Zlib\*(C'\fR and therefore
\&\f(CW\*(C`IO::Zlib\*(C'\fR doesn't support \f(CW\*(C`seek\*(C'\fR 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 \f(CW\*(C`extract_archive\*(C'\fR class method
instead. It will optimize and write to disk immediately.
.IP "Can't you lazy-load data instead?" 4
.IX Item "Can't you lazy-load data instead?"
No, not easily. See previous question.
.IP "How much memory will an X kb tar file need?" 4
.IX 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 \f(CW\*(C`/bin/tar\*(C'\fR instead.
.IP "What do you do with unsupported filetypes in an archive?" 4
.IX Item "What do you do with unsupported filetypes in an archive?"
\&\f(CW\*(C`Unix\*(C'\fR has a few filetypes that aren't supported on other platforms,
like \f(CW\*(C`Win32\*(C'\fR. If we encounter a \f(CW\*(C`hardlink\*(C'\fR or \f(CW\*(C`symlink\*(C'\fR we'll just
try to make a copy of the original file, rather than throwing an error.
.Sp
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).
.Sp
For other filetypes, like \f(CW\*(C`chardevs\*(C'\fR and \f(CW\*(C`blockdevs\*(C'\fR we'll warn that
the extraction of this particular item didn't work.
.IP "I'm using WinZip, or some other non-POSIX client, and files are not being extracted properly!" 4
.IX Item "I'm using WinZip, or some other non-POSIX client, and files are not being extracted properly!"
By default, \f(CW\*(C`Archive::Tar\*(C'\fR is in a completely POSIX-compatible
mode, which uses the POSIX-specification of \f(CW\*(C`tar\*(C'\fR to store files.
For paths greather than 100 characters, this is done using the
\&\f(CW\*(C`POSIX header prefix\*(C'\fR. Non-POSIX-compatible clients may not support
this part of the specification, and may only support the \f(CW\*(C`GNU Extended
Header\*(C'\fR functionality. To facilitate those clients, you can set the
\&\f(CW$Archive::Tar::DO_NOT_USE_PREFIX\fR variable to \f(CW\*(C`true\*(C'\fR. See the 
\&\f(CW\*(C`GLOBAL VARIABLES\*(C'\fR section for details on this variable.
.Sp
Note that \s-1GNU\s0 tar earlier than version 1.14 does not cope well with
the \f(CW\*(C`POSIX header prefix\*(C'\fR. If you use such a version, consider setting
the \f(CW$Archive::Tar::DO_NOT_USE_PREFIX\fR variable to \f(CW\*(C`true\*(C'\fR.
.IP "How do I extract only files that have property X from an archive?" 4
.IX 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.
.Sp
You can do this by filtering a list of \f(CW\*(C`Archive::Tar::File\*(C'\fR objects
based on your criteria. For example, to extract only files that have
the string \f(CW\*(C`foo\*(C'\fR in their title, you would use:
.Sp
.Vb 3
\&    $tar\->extract( 
\&        grep { $_\->full_path =~ /foo/ } $tar\->get_files
\&    );
.Ve
.Sp
This way, you can filter on any attribute of the files in the archive.
Consult the \f(CW\*(C`Archive::Tar::File\*(C'\fR documentation on how to use these
objects.
.IP "How do I access .tar.Z files?" 4
.IX Item "How do I access .tar.Z files?"
The \f(CW\*(C`Archive::Tar\*(C'\fR module can optionally use \f(CW\*(C`Compress::Zlib\*(C'\fR (via
the \f(CW\*(C`IO::Zlib\*(C'\fR module) to access tar files that have been compressed
with \f(CW\*(C`gzip\*(C'\fR. Unfortunately tar files compressed with the Unix \f(CW\*(C`compress\*(C'\fR
utility cannot be read by \f(CW\*(C`Compress::Zlib\*(C'\fR and so cannot be directly
accesses by \f(CW\*(C`Archive::Tar\*(C'\fR.
.Sp
If the \f(CW\*(C`uncompress\*(C'\fR or \f(CW\*(C`gunzip\*(C'\fR programs are available, you can use
one of these workarounds to read \f(CW\*(C`.tar.Z\*(C'\fR files from \f(CW\*(C`Archive::Tar\*(C'\fR
.Sp
Firstly with \f(CW\*(C`uncompress\*(C'\fR
.Sp
.Vb 1
\&    use Archive::Tar;
\&
\&    open F, "uncompress \-c $filename |";
\&    my $tar = Archive::Tar\->new(*F);
\&    ...
.Ve
.Sp
and this with \f(CW\*(C`gunzip\*(C'\fR
.Sp
.Vb 1
\&    use Archive::Tar;
\&
\&    open F, "gunzip \-c $filename |";
\&    my $tar = Archive::Tar\->new(*F);
\&    ...
.Ve
.Sp
Similarly, if the \f(CW\*(C`compress\*(C'\fR program is available, you can use this to
write a \f(CW\*(C`.tar.Z\*(C'\fR file
.Sp
.Vb 2
\&    use Archive::Tar;
\&    use IO::File;
\&
\&    my $fh = new IO::File "| compress \-c >$filename";
\&    my $tar = Archive::Tar\->new();
\&    ...
\&    $tar\->write($fh);
\&    $fh\->close ;
.Ve
.IP "How do I handle Unicode strings?" 4
.IX Item "How do I handle Unicode strings?"
\&\f(CW\*(C`Archive::Tar\*(C'\fR 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.
.Sp
For example, if you add a Unicode string like
.Sp
.Vb 2
\&    # Problem
\&    $tar\->add_data(\*(Aqfile.txt\*(Aq, "Euro: \ex{20AC}");
.Ve
.Sp
then there will be a problem later when the tarfile gets written out
to disk via \f(CW\*(C`$tar\-\*(C'\fR\fIwrite()\fR>:
.Sp
.Vb 1
\&    Wide character in print at .../Archive/Tar.pm line 1014.
.Ve
.Sp
The data was added as a Unicode string and when writing it out to disk,
the \f(CW\*(C`:utf8\*(C'\fR line discipline wasn't set by \f(CW\*(C`Archive::Tar\*(C'\fR, so Perl
tried to convert the string to \s-1ISO\-8859\s0 and failed. The written file
now contains garbage.
.Sp
For this reason, Unicode strings need to be converted to UTF\-8\-encoded
bytestrings before they are handed off to \f(CW\*(C`add_data()\*(C'\fR:
.Sp
.Vb 3
\&    use Encode;
\&    my $data = "Accented character: \ex{20AC}";
\&    $data = encode(\*(Aqutf8\*(Aq, $data);
\&
\&    $tar\->add_data(\*(Aqfile.txt\*(Aq, $data);
.Ve
.Sp
A opposite problem occurs if you extract a UTF8\-encoded file from a 
tarball. Using \f(CW\*(C`get_content()\*(C'\fR on the \f(CW\*(C`Archive::Tar::File\*(C'\fR object
will return its content as a bytestring, not as a Unicode string.
.Sp
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:
.Sp
.Vb 2
\&    use Encode;
\&    my $data = $tar\->get_content();
\&    
\&    # Make it a Unicode string
\&    $data = decode(\*(Aqutf8\*(Aq, $data);
.Ve
.Sp
There is no easy way to provide this functionality in \f(CW\*(C`Archive::Tar\*(C'\fR, 
because a tarball can contain many files, and each of which could be
encoded in a different way.
.SH "TODO"
.IX Header "TODO"
.IP "Check if passed in handles are open for read/write" 4
.IX 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.
.IP "Allow archives to be passed in as string" 4
.IX 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.
.IP "Facilitate processing an opened filehandle of a compressed archive" 4
.IX 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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP "The \s-1GNU\s0 tar specification" 4
.IX Item "The GNU tar specification"
\&\f(CW\*(C`http://www.gnu.org/software/tar/manual/tar.html\*(C'\fR
.IP "The \s-1PAX\s0 format specication" 4
.IX Item "The PAX format specication"
The specifcation which tar derives from; \f(CW\*(C` http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html\*(C'\fR
.ie n .IP "A comparison of \s-1GNU\s0 and \s-1POSIX\s0 tar standards; ""http://www.delorie.com/gnu/docs/tar/tar_114.html""" 4
.el .IP "A comparison of \s-1GNU\s0 and \s-1POSIX\s0 tar standards; \f(CWhttp://www.delorie.com/gnu/docs/tar/tar_114.html\fR" 4
.IX Item "A comparison of GNU and POSIX tar standards; http://www.delorie.com/gnu/docs/tar/tar_114.html"
.PD 0
.IP "\s-1GNU\s0 tar intends to switch to \s-1POSIX\s0 compatibility" 4
.IX Item "GNU tar intends to switch to POSIX compatibility"
.PD
\&\s-1GNU\s0 Tar authors have expressed their intention to become completely
POSIX-compatible; \f(CW\*(C`http://www.gnu.org/software/tar/manual/html_node/Formats.html\*(C'\fR
.IP "A Comparison between various tar implementations" 4
.IX Item "A Comparison between various tar implementations"
Lists known issues and incompatibilities; \f(CW\*(C`http://gd.tuwien.ac.at/utils/archivers/star/README.otherbugs\*(C'\fR
.SH "AUTHOR"
.IX Header "AUTHOR"
This module by Jos Boumans <[e-mail]>.
.PP
Please reports bugs to <bug\-archive\[e-mail]>.
.SH "ACKNOWLEDGEMENTS"
.IX Header "ACKNOWLEDGEMENTS"
Thanks to Sean Burke, Chris Nandor, Chip Salzenberg, Tim Heaney and
especially Andrew Savige for their help and suggestions.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
This module is copyright (c) 2002 \- 2007 Jos Boumans 
<[e-mail]>. All rights reserved.
.PP
This library is free software; you may redistribute and/or modify 
it under the same terms as Perl itself.