Archive::Tar(3) User Contributed Perl Documentation Archive::Tar(3)
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 (unix) 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::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 POSIXspecification
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.
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 ;
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@cpan.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 Jos Boumans <kane@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 v5.8.8 2006-08-01 Archive::Tar(3)
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