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Archive::Tar(3perl) Perl Programmers Reference Guide Archive::Tar(3perl)
NAME
Archive::Tar - module for manipulations of tar archives
SYNOPSIS
use Archive::Tar;
my $tar = Archive::Tar->new;
$tar->read('origin.tgz',1);
$tar->extract();
$tar->add_files('file/foo.pl', 'docs/README');
$tar->add_data('file/baz.txt', 'This is the contents now');
$tar->rename('oldname', 'new/file/name');
$tar->write('files.tar');
DESCRIPTION
Archive::Tar provides an object oriented mechanism for handling tar files. It provides
class methods for quick and easy files handling while also allowing for the creation of
tar file objects for custom manipulation. If you have the IO::Zlib module installed,
Archive::Tar will also support compressed or gzipped tar files.
An object of class Archive::Tar represents a .tar(.gz) archive full of files and things.
Object Methods
Archive::Tar->new( [$file, $compressed] )
Returns a new Tar object. If given any arguments, "new()" calls the "read()" method
automatically, passing on the arguments provided to the "read()" method.
If "new()" is invoked with arguments and the "read()" method fails for any reason, "new()"
returns undef.
$tar->read ( $filename|$handle, $compressed, {opt => 'val'} )
Read the given tar file into memory. The first argument can either be the name of a file
or a reference to an already open filehandle (or an IO::Zlib object if it's compressed)
The second argument indicates whether the file referenced by the first argument is
compressed.
The "read" will replace any previous content in $tar!
The second argument may be considered optional if IO::Zlib is installed, since it will
transparently Do The Right Thing. Archive::Tar will warn if you try to pass a compressed
file if IO::Zlib is not available and simply return.
Note that you can currently not pass a "gzip" compressed filehandle, which is not opened
with "IO::Zlib", nor a string containing the full archive information (either compressed
or uncompressed). These are worth while features, but not currently implemented. See the
"TODO" section.
The third argument can be a hash reference with options. Note that all options are case-
sensitive.
limit
Do not read more than "limit" files. This is useful if you have very big archives, and
are only interested in the first few files.
extract
If set to true, immediately extract entries when reading them. This gives you the same
memory break as the "extract_archive" function. Note however that entries will not be
read into memory, but written straight to disk.
All files are stored internally as "Archive::Tar::File" objects. Please consult the
Archive::Tar::File documentation for details.
Returns the number of files read in scalar context, and a list of "Archive::Tar::File"
objects in list context.
$tar->contains_file( $filename )
Check if the archive contains a certain file. It will return true if the file is in the
archive, false otherwise.
Note however, that this function does an exact match using "eq" on the full path. So it
cannot compensate for case-insensitive file- systems or compare 2 paths to see if they
would point to the same underlying file.
$tar->extract( [@filenames] )
Write files whose names are equivalent to any of the names in @filenames to disk, creating
subdirectories as necessary. This might not work too well under VMS. Under MacPerl, the
file's modification time will be converted to the MacOS zero of time, and appropriate
conversions will be done to the path. However, the length of each element of the path is
not inspected to see whether it's longer than MacOS currently allows (32 characters).
If "extract" is called without a list of file names, the entire contents of the archive
are extracted.
Returns a list of filenames extracted.
$tar->extract_file( $file, [$extract_path] )
Write an entry, whose name is equivalent to the file name provided to disk. Optionally
takes a second parameter, which is the full native path (including filename) the entry
will be written to.
For example:
$tar->extract_file( 'name/in/archive', 'name/i/want/to/give/it' );
$tar->extract_file( $at_file_object, 'name/i/want/to/give/it' );
Returns true on success, false on failure.
$tar->list_files( [\@properties] )
Returns a list of the names of all the files in the archive.
If "list_files()" is passed an array reference as its first argument it returns a list of
hash references containing the requested properties of each file. The following list of
properties is supported: name, size, mtime (last modified date), mode, uid, gid, linkname,
uname, gname, devmajor, devminor, prefix.
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, making it equivalent to calling
"list_files" without arguments.
$tar->get_files( [@filenames] )
Returns the "Archive::Tar::File" objects matching the filenames provided. If no filename
list was passed, all "Archive::Tar::File" objects in the current Tar object are returned.
Please refer to the "Archive::Tar::File" documentation on how to handle these objects.
$tar->get_content( $file )
Return the content of the named file.
$tar->replace_content( $file, $content )
Make the string $content be the content for the file named $file.
$tar->rename( $file, $new_name )
Rename the file of the in-memory archive to $new_name.
Note that you must specify a Unix path for $new_name, since per tar standard, all files in
the archive must be Unix paths.
Returns true on success and false on failure.
$tar->remove (@filenamelist)
Removes any entries with names matching any of the given filenames from the in-memory
archive. Returns a list of "Archive::Tar::File" objects that remain.
$tar->clear
"clear" clears the current in-memory archive. This effectively gives you a 'blank' object,
ready to be filled again. Note that "clear" only has effect on the object, not the
underlying tarfile.
$tar->write ( [$file, $compressed, $prefix] )
Write the in-memory archive to disk. The first argument can either be the name of a file
or a reference to an already open filehandle (a GLOB reference). If the second argument is
true, the module will use IO::Zlib to write the file in a compressed format. If IO::Zlib
is not available, the "write" method will fail and return.
Note that when you pass in a filehandle, the compression argument is ignored, as all files
are printed verbatim to your filehandle. If you wish to enable compression with
filehandles, use an "IO::Zlib" filehandle instead.
Specific levels of compression can be chosen by passing the values 2 through 9 as the
second parameter.
The third argument is an optional prefix. All files will be tucked away in the directory
you specify as prefix. So if you have files 'a' and 'b' in your archive, and you specify
'foo' as prefix, they will be written to the archive as 'foo/a' and 'foo/b'.
If no arguments are given, "write" returns the entire formatted archive as a string, which
could be useful if you'd like to stuff the archive into a socket or a pipe to gzip or
something.
$tar->add_files( @filenamelist )
Takes a list of filenames and adds them to the in-memory archive.
The path to the file is automatically converted to a Unix like equivalent for use in the
archive, and, if on MacOS, the file's modification time is converted from the MacOS epoch
to the Unix epoch. So tar archives created on MacOS with Archive::Tar can be read both
with tar on Unix and applications like suntar or Stuffit Expander on MacOS.
Be aware that the file's type/creator and resource fork will be lost, which is usually
what you want in cross-platform archives.
Returns a list of "Archive::Tar::File" objects that were just added.
$tar->add_data ( $filename, $data, [$opthashref] )
Takes a filename, a scalar full of data and optionally a reference to a hash with specific
options.
Will add a file to the in-memory archive, with name $filename and content $data. Specific
properties can be set using $opthashref. The following list of properties is supported:
name, size, mtime (last modified date), mode, uid, gid, linkname, uname, gname, devmajor,
devminor, prefix, type. (On MacOS, the file's path and modification times are converted
to Unix equivalents.)
Valid values for the file type are the following constants defined in
Archive::Tar::Constants:
FILE
Regular file.
HARDLINK
SYMLINK
Hard and symbolic ("soft") links; linkname should specify target.
CHARDEV
BLOCKDEV
Character and block devices. devmajor and devminor should specify the major and minor
device numbers.
DIR Directory.
FIFO
FIFO (named pipe).
SOCKET
Socket.
Returns the "Archive::Tar::File" object that was just added, or "undef" on failure.
$tar->error( [$BOOL] )
Returns the current errorstring (usually, the last error reported). If a true value was
specified, it will give the "Carp::longmess" equivalent of the error, in effect giving you
a stacktrace.
For backwards compatibility, this error is also available as $Archive::Tar::error although
it is much recommended you use the method call instead.
$tar->setcwd( $cwd );
"Archive::Tar" needs to know the current directory, and it will run "Cwd::cwd()" every
time it extracts a relative entry from the tarfile and saves it in the file system. (As of
version 1.30, however, "Archive::Tar" will use the speed optimization described below
automatically, so it's only relevant if you're using "extract_file()").
Since "Archive::Tar" doesn't change the current directory internally while it is
extracting the items in a tarball, all calls to "Cwd::cwd()" can be avoided if we can
guarantee that the current directory doesn't get changed externally.
To use this performance boost, set the current directory via
use Cwd;
$tar->setcwd( cwd() );
once before calling a function like "extract_file" and "Archive::Tar" will use the current
directory setting from then on and won't call "Cwd::cwd()" internally.
To switch back to the default behaviour, use
$tar->setcwd( undef );
and "Archive::Tar" will call "Cwd::cwd()" internally again.
If you're using "Archive::Tar"'s "exract()" method, "setcwd()" will be called for you.
$bool = $tar->has_io_string
Returns true if we currently have "IO::String" support loaded.
Either "IO::String" or "perlio" support is needed to support writing stringified archives.
Currently, "perlio" is the preferred method, if available.
See the "GLOBAL VARIABLES" section to see how to change this preference.
$bool = $tar->has_perlio
Returns true if we currently have "perlio" support loaded.
This requires "perl-5.8" or higher, compiled with "perlio"
Either "IO::String" or "perlio" support is needed to support writing stringified archives.
Currently, "perlio" is the preferred method, if available.
See the "GLOBAL VARIABLES" section to see how to change this preference.
Class Methods
Archive::Tar->create_archive($file, $compression, @filelist)
Creates a tar file from the list of files provided. The first argument can either be the
name of the tar file to create or a reference to an open file handle (e.g. a GLOB
reference).
The second argument specifies the level of compression to be used, if any. Compression of
tar files requires the installation of the IO::Zlib module. Specific levels of
compression may be requested by passing a value between 2 and 9 as the second argument.
Any other value evaluating as true will result in the default compression level being
used.
Note that when you pass in a filehandle, the compression argument is ignored, as all files
are printed verbatim to your filehandle. If you wish to enable compression with
filehandles, use an "IO::Zlib" filehandle instead.
The remaining arguments list the files to be included in the tar file. These files must
all exist. Any files which don't exist or can't be read are silently ignored.
If the archive creation fails for any reason, "create_archive" will return false. Please
use the "error" method to find the cause of the failure.
Note that this method does not write "on the fly" as it were; it still reads all the files
into memory before writing out the archive. Consult the FAQ below if this is a problem.
Archive::Tar->list_archive ($file, $compressed, [\@properties])
Returns a list of the names of all the files in the archive. The first argument can
either be the name of the tar file to list or a reference to an open file handle (e.g. a
GLOB reference).
If "list_archive()" is passed an array reference as its third argument it returns a list
of hash references containing the requested properties of each file. The following list
of properties is supported: full_path, name, size, mtime (last modified date), mode, uid,
gid, linkname, uname, gname, devmajor, devminor, prefix.
See "Archive::Tar::File" for details about supported properties.
Passing an array reference containing only one element, 'name', is special cased to return
a list of names rather than a list of hash references.
Archive::Tar->extract_archive ($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.
"extract_archive" will return a list of files it extracted. If the archive extraction
fails for any reason, "extract_archive" will return false. Please use the "error" method
to find the cause of the failure.
Archive::Tar->can_handle_compressed_files
A simple checking routine, which will return true if "Archive::Tar" is able to uncompress
compressed archives on the fly with "IO::Zlib", or false if "IO::Zlib" is not installed.
You can use this as a shortcut to determine whether "Archive::Tar" will do what you think
before passing compressed archives to its "read" method.
GLOBAL VARIABLES
$Archive::Tar::FOLLOW_SYMLINK
Set this variable to 1 to make "Archive::Tar" effectively make a copy of the file when
extracting. Default is 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 "write" or "create_archive".
This works just like "/bin/tar"'s "-h" option.
$Archive::Tar::CHOWN
By default, "Archive::Tar" will try to "chown" your files if it is able to. In some cases,
this may not be desired. In that case, set this variable to 0 to disable "chown"-ing, even
if it were possible.
The default is 1.
$Archive::Tar::CHMOD
By default, "Archive::Tar" will try to "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 0 to disable "chmod"-ing.
The default is 1.
$Archive::Tar::DO_NOT_USE_PREFIX
By default, "Archive::Tar" will try to put paths that are over 100 characters in the
"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 $DO_NOT_USE_PREFIX variable to a true value, and
"Archive::Tar" will use an alternate way of dealing with paths over 100 characters by
using the "GNU Extended Header" feature.
Note that clients who do not support the "GNU Extended Header" feature will not be able to
read these archives. Such clients include tars on "Solaris", "Irix" and "AIX".
The default is 0.
$Archive::Tar::DEBUG
Set this variable to 1 to always get the "Carp::longmess" output of the warnings, instead
of the regular "carp". This is the same message you would get by doing:
$tar->error(1);
Defaults to 0.
$Archive::Tar::WARN
Set this variable to 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 1.
$Archive::Tar::error
Holds the last reported error. Kept for historical reasons, but its use is very much
discouraged. Use the "error()" method instead:
warn $tar->error unless $tar->extract;
$Archive::Tar::INSECURE_EXTRACT_MODE
This variable indicates whether "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 "true".
Note that this is a backwards incompatible change from version 1.36 and before.
$Archive::Tar::HAS_PERLIO
This variable holds a boolean indicating if we currently have "perlio" support loaded.
This will be enabled for any perl greater than 5.8 compiled with "perlio".
If you feel strongly about disabling it, set this variable to "false". Note that you will
then need "IO::String" installed to support writing stringified archives.
Don't change this variable unless you really know what you're doing.
$Archive::Tar::HAS_IO_STRING
This variable holds a boolean indicating if we currently have "IO::String" support loaded.
This will be enabled for any perl that has a loadable "IO::String" module.
If you feel strongly about disabling it, set this variable to "false". Note that you will
then need "perlio" support from your perl to be able to write stringified archives.
Don't change this variable unless you really know what you're doing.
FAQ
What's the minimum perl version required to run Archive::Tar?
You will need perl version 5.005_03 or newer.
Isn't Archive::Tar slow?
Yes it is. It's pure perl, so it's a lot slower then your "/bin/tar" However, it's
very portable. If speed is an issue, consider using "/bin/tar" instead.
Isn't Archive::Tar heavier on memory than /bin/tar?
Yes it is, see previous answer. Since "Compress::Zlib" and therefore "IO::Zlib"
doesn't support "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 "extract_archive" class method instead.
It will optimize and write to disk immediately.
Can't you lazy-load data instead?
No, not easily. See previous question.
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
"/bin/tar" instead.
What do you do with unsupported filetypes in an archive?
"Unix" has a few filetypes that aren't supported on other platforms, like "Win32". If
we encounter a "hardlink" or "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 "chardevs" and "blockdevs" we'll warn that the extraction of
this particular item didn't work.
I'm using WinZip, or some other non-POSIX client, and files are not being extracted
properly!
By default, "Archive::Tar" is in a completely POSIX-compatible mode, which uses the
POSIX-specification of "tar" to store files. For paths greather than 100 characters,
this is done using the "POSIX header prefix". Non-POSIX-compatible clients may not
support this part of the specification, and may only support the "GNU Extended Header"
functionality. To facilitate those clients, you can set the
$Archive::Tar::DO_NOT_USE_PREFIX variable to "true". See the "GLOBAL VARIABLES"
section for details on this variable.
Note that GNU tar earlier than version 1.14 does not cope well with the "POSIX header
prefix". If you use such a version, consider setting the
$Archive::Tar::DO_NOT_USE_PREFIX variable to "true".
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 "Archive::Tar::File" objects based on your
criteria. For example, to extract only files that have the string "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
"Archive::Tar::File" documentation on how to use these objects.
How do I access .tar.Z files?
The "Archive::Tar" module can optionally use "Compress::Zlib" (via the "IO::Zlib"
module) to access tar files that have been compressed with "gzip". Unfortunately tar
files compressed with the Unix "compress" utility cannot be read by "Compress::Zlib"
and so cannot be directly accesses by "Archive::Tar".
If the "uncompress" or "gunzip" programs are available, you can use one of these
workarounds to read ".tar.Z" files from "Archive::Tar"
Firstly with "uncompress"
use Archive::Tar;
open F, "uncompress -c $filename |";
my $tar = Archive::Tar->new(*F);
...
and this with "gunzip"
use Archive::Tar;
open F, "gunzip -c $filename |";
my $tar = Archive::Tar->new(*F);
...
Similarly, if the "compress" program is available, you can use this to write a
".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 ;
How do I handle Unicode strings?
"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
$tar->add_data('file.txt', "Euro: \x{20AC}");
then there will be a problem later when the tarfile gets written out to disk via
"$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 ":utf8"
line discipline wasn't set by "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 "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
"get_content()" on the "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 "Archive::Tar", because a
tarball can contain many files, and each of which could be encoded in a different way.
TODO
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.
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.
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.
SEE ALSO
The GNU tar specification
"http://www.gnu.org/software/tar/manual/tar.html"
The PAX format specication
The specifcation which tar derives from; "
http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html"
A comparison of GNU and POSIX tar standards;
"http://www.delorie.com/gnu/docs/tar/tar_114.html"
GNU tar intends to switch to POSIX compatibility
GNU Tar authors have expressed their intention to become completely POSIX-compatible;
"http://www.gnu.org/software/tar/manual/html_node/Formats.html"
A Comparison between various tar implementations
Lists known issues and incompatibilities;
"http://gd.tuwien.ac.at/utils/archivers/star/README.otherbugs"
AUTHOR
This module by Jos Boumans <kane AT cpan.org>.
Please reports bugs to <bug-archive-tar AT rt.org>.
ACKNOWLEDGEMENTS
Thanks to Sean Burke, Chris Nandor, Chip Salzenberg, Tim Heaney and especially Andrew
Savige for their help and suggestions.
COPYRIGHT
This module is copyright (c) 2002 - 2007 Jos Boumans <kane AT cpan.org>. All rights reserved.
This library is free software; you may redistribute and/or modify it under the same terms
as Perl itself.
perl v5.10.0 2011-06-30 Archive::Tar(3perl)
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