Archive::Tar man page on aLinux

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Archive::Tar(3)	       Perl Programmers Reference Guide	       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 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@cpan.org>.

       Please reports bugs to <bug-archive-tar@rt.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 - 2007 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 v5.10.0			  2007-12-18		       Archive::Tar(3)
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