Provided by: libarchive-tar-wrapper-perl_0.38-2_all 
NAME
Archive::Tar::Wrapper - API wrapper around the 'tar' utility
SYNOPSIS
use Archive::Tar::Wrapper;
my $arch = Archive::Tar::Wrapper->new();
# Open a tarball, expand it into a temporary directory
$arch->read("archive.tgz");
# Iterate over all entries in the archive
$arch->list_reset(); # Reset Iterator
# Iterate through archive
while(my $entry = $arch->list_next()) {
my($tar_path, $phys_path) = @$entry;
print "$tar_path\n";
}
# Get a huge list with all entries
for my $entry (@{$arch->list_all()}) {
my($tar_path, $real_path) = @$entry;
print "Tarpath: $tar_path Tempfile: $real_path\n";
}
# Add a new entry
$arch->add($logic_path, $file_or_stringref);
# Remove an entry
$arch->remove($logic_path);
# Find the physical location of a temporary file
my($tmp_path) = $arch->locate($tar_path);
# Create a tarball
$arch->write($tarfile, $compress);
DESCRIPTION
Archive::Tar::Wrapper is an API wrapper around the "tar" command line program. It never
stores anything in memory, but works on temporary directory structures on disk instead. It
provides a mapping between the logical paths in the tarball and the 'real' files in the
temporary directory on disk.
It differs from Archive::Tar in two ways:
• Archive::Tar::Wrapper almost doesn't hold anything in memory (see "write" method),
instead using disk as storage.
• Archive::Tar::Wrapper is 100% compliant with the platform's "tar" utility because it
uses it internally.
METHODS
new
my $arch = Archive::Tar::Wrapper->new();
Constructor for the "tar" wrapper class. Finds the "tar" executable by searching "PATH"
and returning the first hit. In case you want to use a different tar executable, you can
specify it as a parameter:
my $arch = Archive::Tar::Wrapper->new(tar => '/path/to/tar');
Since Archive::Tar::Wrapper creates temporary directories to store "tar" data, the
location of the temporary directory can be specified:
my $arch = Archive::Tar::Wrapper->new(tmpdir => '/path/to/tmpdir');
Tremendous performance increases can be achieved if the temporary directory is located on
a RAM disk. Check the "Using RAM Disks" in Archive::Tar::Wrapper section for details.
Additional options can be passed to the "tar" command by using the "tar_read_options" and
"tar_write_options" parameters. Example:
my $arch = Archive::Tar::Wrapper->new(
tar_read_options => 'p'
);
will use "tar xfp archive.tgz" to extract the tarball instead of just "tar xf
archive.tgz". GNU tar supports even more options, these can be passed in via
my $arch = Archive::Tar::Wrapper->new(
tar_gnu_read_options => ["--numeric-owner"],
);
Similarly, "tar_gnu_write_options" can be used to provide additional options for GNU tar
implementations. For example, the tar object
my $tar = Archive::Tar::Wrapper->new(
tar_gnu_write_options => ["--exclude=foo"],
);
will call the "tar" utility internally like
tar cf tarfile --exclude=foo ...
when the "write" method gets called.
By default, the "list_*()" functions will return only file entries: directories will be
suppressed. To have "list_*()" return directories as well, use
my $arch = Archive::Tar::Wrapper->new(
dirs => 1
);
If more files are added to a tarball than the command line can handle,
Archive::Tar::Wrapper will switch from using the command
tar cfv tarfile file1 file2 file3 ...
to
tar cfv tarfile -T filelist
where "filelist" is a file containing all file to be added. The default for this switch is
512, but it can be changed by setting the parameter "max_cmd_line_args":
my $arch = Archive::Tar::Wrapper->new(
max_cmd_line_args => 1024
);
The expectable parameters are:
• tar
• tmpdir
• tar_read_options
• tar_write_options
• tar_gnu_read_options
• tar_gnu_write_options
• max_cmd_line_args: defaults to 512
• ramdisk
Returns a new instance of the class.
read
$arch->read("archive.tgz");
"read()" opens the given tarball, expands it into a temporary directory and returns 1 on
success or "undef" on failure. The temporary directory holding the tar data gets cleaned
up when $arch goes out of scope.
"read" handles both compressed and uncompressed files. To find out if a file is compressed
or uncompressed, it tries to guess by extension, then by checking the first couple of
bytes in the tarfile.
If only a limited number of files is needed from a tarball, they can be specified after
the tarball name:
$arch->read("archive.tgz", "path/file.dat", "path/sub/another.txt");
The file names are passed unmodified to the "tar" command, make sure that the file paths
match exactly what's in the tarball, otherwise "read()" will fail.
list_reset
$arch->list_reset()
Resets the list iterator. To be used before the first call to "list_next()".
tardir
$arch->tardir();
Return the directory the tarball was unpacked in. This is sometimes useful to play dirty
tricks on Archive::Tar::Wrapper by mass-manipulating unpacked files before wrapping them
back up into the tarball.
is_compressed
Returns a string to identify if the tarball is compressed or not.
Expect as parameter a string with the path to the tarball.
Returns:
• a "z" character if the file is compressed with gzip.
• a "j" character if the file is compressed with bzip2.
• a "" character if the file is not compressed at all.
locate
$arch->locate($logic_path);
Finds the physical location of a file, specified by $logic_path, which is the virtual path
of the file within the tarball. Returns a path to the temporary file Archive::Tar::Wrapper
created to manipulate the tarball on disk.
add
$arch->add($logic_path, $file_or_stringref, [$options]);
Add a new file to the tarball. $logic_path is the virtual path of the file within the
tarball. $file_or_stringref is either a scalar, in which case it holds the physical path
of a file on disk to be transferred (i.e. copied) to the tarball, or it is a reference to
a scalar, in which case its content is interpreted to be the data of the file.
If no additional parameters are given, permissions and user/group id settings of a file to
be added are copied. If you want different settings, specify them in the options hash:
$arch->add($logic_path, $stringref,
{ perm => 0755, uid => 123, gid => 10 });
If $file_or_stringref is a reference to a Unicode string, the "binmode" option has to be
set to make sure the string gets written as proper UTF-8 into the tarfile:
$arch->add($logic_path, $stringref, { binmode => ":utf8" });
perm_cp
Copies the permissions from a file to another.
Expects as parameters:
1. string of the path to the file which permissions will be copied from.
2. string of the path to the file which permissions will be copied to.
Returns 1 if everything works as expected.
perm_get
Gets the permissions from a file.
Expects as parameter the path to the source file.
Returns an array reference with only the permissions values, as returned by "stat".
perm_set
Sets the permission on a file.
Expects as parameters:
1. The path to the file where the permissions should be applied to.
2. An array reference with the permissions (see "perm_set")
Returns 1 if everything goes fine.
Ignore errors here, as we can't change uid/gid unless we're the superuser (see LIMITATIONS
section).
remove
$arch->remove($logic_path);
Removes a file from the tarball. $logic_path is the virtual path of the file within the
tarball.
list_all
my $items = $arch->list_all();
Returns a reference to a (possibly huge) array of items in the tarfile. Each item is a
reference to an array, containing two elements: the relative path of the item in the
tarfile and the physical path to the unpacked file or directory on disk.
To iterate over the list, the following construct can be used:
# Get a huge list with all entries
for my $entry (@{$arch->list_all()}) {
my($tar_path, $real_path) = @$entry;
print "Tarpath: $tar_path Tempfile: $real_path\n";
}
If the list of items in the tarfile is big, use "list_reset()" and "list_next()" instead
of "list_all".
list_next
my ($tar_path, $phys_path, $type) = $arch->list_next();
Returns the next item in the tarfile. It returns a list of three scalars: the relative
path of the item in the tarfile, the physical path to the unpacked file or directory on
disk, and the type of the entry (f=file, d=directory, l=symlink). Note that by default,
Archive::Tar::Wrapper won't display directories, unless the "dirs" parameter is set when
running the constructor.
write
$arch->write($tarfile, $compress);
Write out the tarball by tarring up all temporary files and directories and store it in
$tarfile on disk. If $compress holds a true value, compression is used.
is_gnu
$arch->is_gnu();
Checks if the tar executable is a GNU tar by running 'tar --version' and parsing the
output for "GNU".
Returns true or false (in Perl terms).
is_bsd
$arch->is_bsd();
Same as "is_gnu()", but for BSD.
ramdisk_mount
Mounts a RAM disk.
It executes the "mount" program under the hood to mount a RAM disk.
Expects as parameter a hash with options to mount the RAM disk, like:
• size
• type (most probably "tmpfs")
• tmpdir
Returns 1 if everything goes fine.
Be sure to check the "Using RAM Disks" in Archive::Tar::Wrapper for full details on using
RAM disks.
ramdisk_unmount
Unmounts the RAM disk already mounted with "ramdisk_mount".
Don't expect parameters and returns 1 if everything goes fine.
Be sure to check the "Using RAM Disks" in Archive::Tar::Wrapper for full details on using
RAM disks.
Using RAM Disks
On Linux, it's quite easy to create a RAM disk and achieve tremendous speedups while
untarring or modifying a tarball. You can either create the RAM disk by hand by running
# mkdir -p /mnt/myramdisk
# mount -t tmpfs -o size=20m tmpfs /mnt/myramdisk
and then feeding the ramdisk as a temporary directory to Archive::Tar::Wrapper, like
my $tar = Archive::Tar::Wrapper->new( tmpdir => '/mnt/myramdisk' );
or using Archive::Tar::Wrapper's built-in option "ramdisk":
my $tar = Archive::Tar::Wrapper->new(
ramdisk => {
type => 'tmpfs',
size => '20m', # 20 MB
},
);
Only drawback with the latter option is that creating the RAM disk needs to be performed
as root, which often isn't desirable for security reasons. For this reason,
Archive::Tar::Wrapper offers a utility functions that mounts the RAM disk and returns the
temporary directory it's located in:
# Create new ramdisk (as root):
my $tmpdir = Archive::Tar::Wrapper->ramdisk_mount(
type => 'tmpfs',
size => '20m', # 20 MB
);
# Delete a ramdisk (as root):
Archive::Tar::Wrapper->ramdisk_unmount();
Optionally, the "ramdisk_mount()" command accepts a "tmpdir" parameter pointing to a
temporary directory for the RAM disk if you wish to set it yourself instead of letting
Archive::Tar::Wrapper create it automatically.
KNOWN LIMITATIONS
• Currently, only "tar" programs supporting the "z" option (for
compressing/decompressing) are supported. Future version will use "gzip"
alternatively.
• Currently, you can't add empty directories to a tarball directly. You could add a
temporary file within a directory, and then "remove()" the file.
• If you delete a file, the empty directories it was located in stay in the tarball. You
could try to "locate()" them and delete them. This will be fixed, though.
• Filenames containing newlines are causing problems with the list iterators. To be
fixed.
• If you ask Archive::Tar::Wrapper to add a file to a tarball, it copies it into a
temporary directory and then calls the system tar to wrap up that directory into a
tarball.
This approach has limitations when it comes to file permissions: If the file to be
added belongs to a different user/group, Archive::Tar::Wrapper will adjust the
uid/gid/permissions of the target file in the temporary directory to reflect the
original file's settings, to make sure the system tar will add it like that to the
tarball, just like a regular tar run on the original file would. But this will fail of
course if the original file's uid is different from the current user's, unless the
script is running with superuser rights. The tar program by itself (without
Archive::Tar::Wrapper) works differently: It'll just make a note of a file's
uid/gid/permissions in the tarball (which it can do without superuser rights) and upon
extraction, it'll adjust the permissions of newly generated files if the -p option is
given (default for superuser).
BUGS
Archive::Tar::Wrapper doesn't currently handle filenames with embedded newlines.
Microsoft Windows support
Support on Microsoft Windows is limited.
Versions below Windows 10 will not be supported for desktops, and for servers only Windows
2012 and above.
The GNU "tar.exe" program doesn't work properly with the current interface of
Archive::Tar::Wrapper.
You must use the "bsdtar.exe" and make sure it appears first in the "PATH" environment
variable than the GNU tar (if it is installed). See <http://libarchive.org/> for details
about how to download and install "bsdtar.exe", or go to
<http://gnuwin32.sourceforge.net/packages.html> for a direct download. Be sure to look for
the "bzip2" program package to install it as well.
Windows 10 might come already with "bsdtar" program already installed. Please search for
that on the appropriate page (Microsoft keeps changing the link to keep track of it here).
Having spaces in the path string to the tar program might be an issue too. Although there
is some effort in terms of workaround it, you best might avoid it completely by installing
in a different path than "C:\Program Files". Installing both "bsdtar" and "bzip2" in
"C:\GnuWin32" will probably be enough when running the installers.
LEGALESE
This software is copyright (c) 2005 of Mike Schilli.
This program is free software: you can redistribute it and/or modify it under the terms of
the GNU General Public License as published by the Free Software Foundation, either
version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with Archive-Tar-
Wrapper. If not, see <http://www.gnu.org/licenses/>.
SEE ALSO
• Linux Gazette article from Ben Okopnik, issue 87
<https://linuxgazette.net/87/okopnik.html>.
AUTHOR
2005, Mike Schilli <cpan@perlmeister.com>
MAINTAINER
2018, Alceu Rodrigues de Freitas Junior <arfreitas@cpan.org>