719 lines
25 KiB
ReStructuredText
719 lines
25 KiB
ReStructuredText
:mod:`tarfile` --- Read and write tar archive files
|
|
===================================================
|
|
|
|
.. module:: tarfile
|
|
:synopsis: Read and write tar-format archive files.
|
|
|
|
|
|
.. moduleauthor:: Lars Gustäbel <lars@gustaebel.de>
|
|
.. sectionauthor:: Lars Gustäbel <lars@gustaebel.de>
|
|
|
|
|
|
The :mod:`tarfile` module makes it possible to read and write tar
|
|
archives, including those using gzip or bz2 compression.
|
|
(:file:`.zip` files can be read and written using the :mod:`zipfile` module.)
|
|
|
|
Some facts and figures:
|
|
|
|
* reads and writes :mod:`gzip` and :mod:`bz2` compressed archives.
|
|
|
|
* read/write support for the POSIX.1-1988 (ustar) format.
|
|
|
|
* read/write support for the GNU tar format including *longname* and *longlink*
|
|
extensions, read-only support for the *sparse* extension.
|
|
|
|
* read/write support for the POSIX.1-2001 (pax) format.
|
|
|
|
* handles directories, regular files, hardlinks, symbolic links, fifos,
|
|
character devices and block devices and is able to acquire and restore file
|
|
information like timestamp, access permissions and owner.
|
|
|
|
|
|
.. function:: open(name=None, mode='r', fileobj=None, bufsize=10240, \*\*kwargs)
|
|
|
|
Return a :class:`TarFile` object for the pathname *name*. For detailed
|
|
information on :class:`TarFile` objects and the keyword arguments that are
|
|
allowed, see :ref:`tarfile-objects`.
|
|
|
|
*mode* has to be a string of the form ``'filemode[:compression]'``, it defaults
|
|
to ``'r'``. Here is a full list of mode combinations:
|
|
|
|
+------------------+---------------------------------------------+
|
|
| mode | action |
|
|
+==================+=============================================+
|
|
| ``'r' or 'r:*'`` | Open for reading with transparent |
|
|
| | compression (recommended). |
|
|
+------------------+---------------------------------------------+
|
|
| ``'r:'`` | Open for reading exclusively without |
|
|
| | compression. |
|
|
+------------------+---------------------------------------------+
|
|
| ``'r:gz'`` | Open for reading with gzip compression. |
|
|
+------------------+---------------------------------------------+
|
|
| ``'r:bz2'`` | Open for reading with bzip2 compression. |
|
|
+------------------+---------------------------------------------+
|
|
| ``'a' or 'a:'`` | Open for appending with no compression. The |
|
|
| | file is created if it does not exist. |
|
|
+------------------+---------------------------------------------+
|
|
| ``'w' or 'w:'`` | Open for uncompressed writing. |
|
|
+------------------+---------------------------------------------+
|
|
| ``'w:gz'`` | Open for gzip compressed writing. |
|
|
+------------------+---------------------------------------------+
|
|
| ``'w:bz2'`` | Open for bzip2 compressed writing. |
|
|
+------------------+---------------------------------------------+
|
|
|
|
Note that ``'a:gz'`` or ``'a:bz2'`` is not possible. If *mode* is not suitable
|
|
to open a certain (compressed) file for reading, :exc:`ReadError` is raised. Use
|
|
*mode* ``'r'`` to avoid this. If a compression method is not supported,
|
|
:exc:`CompressionError` is raised.
|
|
|
|
If *fileobj* is specified, it is used as an alternative to a file object opened
|
|
for *name*. It is supposed to be at position 0.
|
|
|
|
For special purposes, there is a second format for *mode*:
|
|
``'filemode|[compression]'``. :func:`tarfile.open` will return a :class:`TarFile`
|
|
object that processes its data as a stream of blocks. No random seeking will
|
|
be done on the file. If given, *fileobj* may be any object that has a
|
|
:meth:`read` or :meth:`write` method (depending on the *mode*). *bufsize*
|
|
specifies the blocksize and defaults to ``20 * 512`` bytes. Use this variant
|
|
in combination with e.g. ``sys.stdin``, a socket file object or a tape
|
|
device. However, such a :class:`TarFile` object is limited in that it does
|
|
not allow to be accessed randomly, see :ref:`tar-examples`. The currently
|
|
possible modes:
|
|
|
|
+-------------+--------------------------------------------+
|
|
| Mode | Action |
|
|
+=============+============================================+
|
|
| ``'r|*'`` | Open a *stream* of tar blocks for reading |
|
|
| | with transparent compression. |
|
|
+-------------+--------------------------------------------+
|
|
| ``'r|'`` | Open a *stream* of uncompressed tar blocks |
|
|
| | for reading. |
|
|
+-------------+--------------------------------------------+
|
|
| ``'r|gz'`` | Open a gzip compressed *stream* for |
|
|
| | reading. |
|
|
+-------------+--------------------------------------------+
|
|
| ``'r|bz2'`` | Open a bzip2 compressed *stream* for |
|
|
| | reading. |
|
|
+-------------+--------------------------------------------+
|
|
| ``'w|'`` | Open an uncompressed *stream* for writing. |
|
|
+-------------+--------------------------------------------+
|
|
| ``'w|gz'`` | Open an gzip compressed *stream* for |
|
|
| | writing. |
|
|
+-------------+--------------------------------------------+
|
|
| ``'w|bz2'`` | Open an bzip2 compressed *stream* for |
|
|
| | writing. |
|
|
+-------------+--------------------------------------------+
|
|
|
|
|
|
.. class:: TarFile
|
|
|
|
Class for reading and writing tar archives. Do not use this class directly,
|
|
better use :func:`tarfile.open` instead. See :ref:`tarfile-objects`.
|
|
|
|
|
|
.. function:: is_tarfile(name)
|
|
|
|
Return :const:`True` if *name* is a tar archive file, that the :mod:`tarfile`
|
|
module can read.
|
|
|
|
|
|
The :mod:`tarfile` module defines the following exceptions:
|
|
|
|
|
|
.. exception:: TarError
|
|
|
|
Base class for all :mod:`tarfile` exceptions.
|
|
|
|
|
|
.. exception:: ReadError
|
|
|
|
Is raised when a tar archive is opened, that either cannot be handled by the
|
|
:mod:`tarfile` module or is somehow invalid.
|
|
|
|
|
|
.. exception:: CompressionError
|
|
|
|
Is raised when a compression method is not supported or when the data cannot be
|
|
decoded properly.
|
|
|
|
|
|
.. exception:: StreamError
|
|
|
|
Is raised for the limitations that are typical for stream-like :class:`TarFile`
|
|
objects.
|
|
|
|
|
|
.. exception:: ExtractError
|
|
|
|
Is raised for *non-fatal* errors when using :meth:`TarFile.extract`, but only if
|
|
:attr:`TarFile.errorlevel`\ ``== 2``.
|
|
|
|
|
|
.. exception:: HeaderError
|
|
|
|
Is raised by :meth:`TarInfo.frombuf` if the buffer it gets is invalid.
|
|
|
|
|
|
|
|
Each of the following constants defines a tar archive format that the
|
|
:mod:`tarfile` module is able to create. See section :ref:`tar-formats` for
|
|
details.
|
|
|
|
|
|
.. data:: USTAR_FORMAT
|
|
|
|
POSIX.1-1988 (ustar) format.
|
|
|
|
|
|
.. data:: GNU_FORMAT
|
|
|
|
GNU tar format.
|
|
|
|
|
|
.. data:: PAX_FORMAT
|
|
|
|
POSIX.1-2001 (pax) format.
|
|
|
|
|
|
.. data:: DEFAULT_FORMAT
|
|
|
|
The default format for creating archives. This is currently :const:`GNU_FORMAT`.
|
|
|
|
|
|
The following variables are available on module level:
|
|
|
|
|
|
.. data:: ENCODING
|
|
|
|
The default character encoding i.e. the value from either
|
|
:func:`sys.getfilesystemencoding` or :func:`sys.getdefaultencoding`.
|
|
|
|
|
|
.. seealso::
|
|
|
|
Module :mod:`zipfile`
|
|
Documentation of the :mod:`zipfile` standard module.
|
|
|
|
`GNU tar manual, Basic Tar Format <http://www.gnu.org/software/tar/manual/html_node/Standard.html>`_
|
|
Documentation for tar archive files, including GNU tar extensions.
|
|
|
|
|
|
.. _tarfile-objects:
|
|
|
|
TarFile Objects
|
|
---------------
|
|
|
|
The :class:`TarFile` object provides an interface to a tar archive. A tar
|
|
archive is a sequence of blocks. An archive member (a stored file) is made up of
|
|
a header block followed by data blocks. It is possible to store a file in a tar
|
|
archive several times. Each archive member is represented by a :class:`TarInfo`
|
|
object, see :ref:`tarinfo-objects` for details.
|
|
|
|
A :class:`TarFile` object can be used as a context manager in a :keyword:`with`
|
|
statement. It will automatically be closed when the block is completed. Please
|
|
note that in the event of an exception an archive opened for writing will not
|
|
be finalized; only the internally used file object will be closed. See the
|
|
:ref:`tar-examples` section for a use case.
|
|
|
|
.. versionadded:: 3.2
|
|
Added support for the context manager protocol.
|
|
|
|
.. class:: TarFile(name=None, mode='r', fileobj=None, format=DEFAULT_FORMAT, tarinfo=TarInfo, dereference=False, ignore_zeros=False, encoding=ENCODING, errors='surrogateescape', pax_headers=None, debug=0, errorlevel=0)
|
|
|
|
All following arguments are optional and can be accessed as instance attributes
|
|
as well.
|
|
|
|
*name* is the pathname of the archive. It can be omitted if *fileobj* is given.
|
|
In this case, the file object's :attr:`name` attribute is used if it exists.
|
|
|
|
*mode* is either ``'r'`` to read from an existing archive, ``'a'`` to append
|
|
data to an existing file or ``'w'`` to create a new file overwriting an existing
|
|
one.
|
|
|
|
If *fileobj* is given, it is used for reading or writing data. If it can be
|
|
determined, *mode* is overridden by *fileobj*'s mode. *fileobj* will be used
|
|
from position 0.
|
|
|
|
.. note::
|
|
|
|
*fileobj* is not closed, when :class:`TarFile` is closed.
|
|
|
|
*format* controls the archive format. It must be one of the constants
|
|
:const:`USTAR_FORMAT`, :const:`GNU_FORMAT` or :const:`PAX_FORMAT` that are
|
|
defined at module level.
|
|
|
|
The *tarinfo* argument can be used to replace the default :class:`TarInfo` class
|
|
with a different one.
|
|
|
|
If *dereference* is :const:`False`, add symbolic and hard links to the archive. If it
|
|
is :const:`True`, add the content of the target files to the archive. This has no
|
|
effect on systems that do not support symbolic links.
|
|
|
|
If *ignore_zeros* is :const:`False`, treat an empty block as the end of the archive.
|
|
If it is :const:`True`, skip empty (and invalid) blocks and try to get as many members
|
|
as possible. This is only useful for reading concatenated or damaged archives.
|
|
|
|
*debug* can be set from ``0`` (no debug messages) up to ``3`` (all debug
|
|
messages). The messages are written to ``sys.stderr``.
|
|
|
|
If *errorlevel* is ``0``, all errors are ignored when using :meth:`TarFile.extract`.
|
|
Nevertheless, they appear as error messages in the debug output, when debugging
|
|
is enabled. If ``1``, all *fatal* errors are raised as :exc:`OSError` or
|
|
:exc:`IOError` exceptions. If ``2``, all *non-fatal* errors are raised as
|
|
:exc:`TarError` exceptions as well.
|
|
|
|
The *encoding* and *errors* arguments define the character encoding to be
|
|
used for reading or writing the archive and how conversion errors are going
|
|
to be handled. The default settings will work for most users.
|
|
See section :ref:`tar-unicode` for in-depth information.
|
|
|
|
.. versionchanged:: 3.2
|
|
Use ``'surrogateescape'`` as the default for the *errors* argument.
|
|
|
|
The *pax_headers* argument is an optional dictionary of strings which
|
|
will be added as a pax global header if *format* is :const:`PAX_FORMAT`.
|
|
|
|
|
|
.. method:: TarFile.open(...)
|
|
|
|
Alternative constructor. The :func:`tarfile.open` function is actually a
|
|
shortcut to this classmethod.
|
|
|
|
|
|
.. method:: TarFile.getmember(name)
|
|
|
|
Return a :class:`TarInfo` object for member *name*. If *name* can not be found
|
|
in the archive, :exc:`KeyError` is raised.
|
|
|
|
.. note::
|
|
|
|
If a member occurs more than once in the archive, its last occurrence is assumed
|
|
to be the most up-to-date version.
|
|
|
|
|
|
.. method:: TarFile.getmembers()
|
|
|
|
Return the members of the archive as a list of :class:`TarInfo` objects. The
|
|
list has the same order as the members in the archive.
|
|
|
|
|
|
.. method:: TarFile.getnames()
|
|
|
|
Return the members as a list of their names. It has the same order as the list
|
|
returned by :meth:`getmembers`.
|
|
|
|
|
|
.. method:: TarFile.list(verbose=True)
|
|
|
|
Print a table of contents to ``sys.stdout``. If *verbose* is :const:`False`,
|
|
only the names of the members are printed. If it is :const:`True`, output
|
|
similar to that of :program:`ls -l` is produced.
|
|
|
|
|
|
.. method:: TarFile.next()
|
|
|
|
Return the next member of the archive as a :class:`TarInfo` object, when
|
|
:class:`TarFile` is opened for reading. Return :const:`None` if there is no more
|
|
available.
|
|
|
|
|
|
.. method:: TarFile.extractall(path=".", members=None)
|
|
|
|
Extract all members from the archive to the current working directory or
|
|
directory *path*. If optional *members* is given, it must be a subset of the
|
|
list returned by :meth:`getmembers`. Directory information like owner,
|
|
modification time and permissions are set after all members have been extracted.
|
|
This is done to work around two problems: A directory's modification time is
|
|
reset each time a file is created in it. And, if a directory's permissions do
|
|
not allow writing, extracting files to it will fail.
|
|
|
|
.. warning::
|
|
|
|
Never extract archives from untrusted sources without prior inspection.
|
|
It is possible that files are created outside of *path*, e.g. members
|
|
that have absolute filenames starting with ``"/"`` or filenames with two
|
|
dots ``".."``.
|
|
|
|
|
|
.. method:: TarFile.extract(member, path="")
|
|
|
|
Extract a member from the archive to the current working directory, using its
|
|
full name. Its file information is extracted as accurately as possible. *member*
|
|
may be a filename or a :class:`TarInfo` object. You can specify a different
|
|
directory using *path*.
|
|
|
|
.. note::
|
|
|
|
The :meth:`extract` method does not take care of several extraction issues.
|
|
In most cases you should consider using the :meth:`extractall` method.
|
|
|
|
.. warning::
|
|
|
|
See the warning for :meth:`extractall`.
|
|
|
|
|
|
.. method:: TarFile.extractfile(member)
|
|
|
|
Extract a member from the archive as a file object. *member* may be a filename
|
|
or a :class:`TarInfo` object. If *member* is a regular file, a file-like object
|
|
is returned. If *member* is a link, a file-like object is constructed from the
|
|
link's target. If *member* is none of the above, :const:`None` is returned.
|
|
|
|
.. note::
|
|
|
|
The file-like object is read-only. It provides the methods
|
|
:meth:`read`, :meth:`readline`, :meth:`readlines`, :meth:`seek`, :meth:`tell`,
|
|
and :meth:`close`, and also supports iteration over its lines.
|
|
|
|
|
|
.. method:: TarFile.add(name, arcname=None, recursive=True, exclude=None, filter=None)
|
|
|
|
Add the file *name* to the archive. *name* may be any type of file (directory,
|
|
fifo, symbolic link, etc.). If given, *arcname* specifies an alternative name
|
|
for the file in the archive. Directories are added recursively by default. This
|
|
can be avoided by setting *recursive* to :const:`False`. If *exclude* is given,
|
|
it must be a function that takes one filename argument and returns a boolean
|
|
value. Depending on this value the respective file is either excluded
|
|
(:const:`True`) or added (:const:`False`). If *filter* is specified it must
|
|
be a function that takes a :class:`TarInfo` object argument and returns the
|
|
changed :class:`TarInfo` object. If it instead returns :const:`None` the :class:`TarInfo`
|
|
object will be excluded from the archive. See :ref:`tar-examples` for an
|
|
example.
|
|
|
|
.. versionchanged:: 3.2
|
|
Added the *filter* parameter.
|
|
|
|
.. deprecated:: 3.2
|
|
The *exclude* parameter is deprecated, please use the *filter* parameter
|
|
instead.
|
|
|
|
|
|
.. method:: TarFile.addfile(tarinfo, fileobj=None)
|
|
|
|
Add the :class:`TarInfo` object *tarinfo* to the archive. If *fileobj* is given,
|
|
``tarinfo.size`` bytes are read from it and added to the archive. You can
|
|
create :class:`TarInfo` objects using :meth:`gettarinfo`.
|
|
|
|
.. note::
|
|
|
|
On Windows platforms, *fileobj* should always be opened with mode ``'rb'`` to
|
|
avoid irritation about the file size.
|
|
|
|
|
|
.. method:: TarFile.gettarinfo(name=None, arcname=None, fileobj=None)
|
|
|
|
Create a :class:`TarInfo` object for either the file *name* or the file object
|
|
*fileobj* (using :func:`os.fstat` on its file descriptor). You can modify some
|
|
of the :class:`TarInfo`'s attributes before you add it using :meth:`addfile`.
|
|
If given, *arcname* specifies an alternative name for the file in the archive.
|
|
|
|
|
|
.. method:: TarFile.close()
|
|
|
|
Close the :class:`TarFile`. In write mode, two finishing zero blocks are
|
|
appended to the archive.
|
|
|
|
|
|
.. attribute:: TarFile.pax_headers
|
|
|
|
A dictionary containing key-value pairs of pax global headers.
|
|
|
|
|
|
|
|
.. _tarinfo-objects:
|
|
|
|
TarInfo Objects
|
|
---------------
|
|
|
|
A :class:`TarInfo` object represents one member in a :class:`TarFile`. Aside
|
|
from storing all required attributes of a file (like file type, size, time,
|
|
permissions, owner etc.), it provides some useful methods to determine its type.
|
|
It does *not* contain the file's data itself.
|
|
|
|
:class:`TarInfo` objects are returned by :class:`TarFile`'s methods
|
|
:meth:`getmember`, :meth:`getmembers` and :meth:`gettarinfo`.
|
|
|
|
|
|
.. class:: TarInfo(name="")
|
|
|
|
Create a :class:`TarInfo` object.
|
|
|
|
|
|
.. method:: TarInfo.frombuf(buf)
|
|
|
|
Create and return a :class:`TarInfo` object from string buffer *buf*.
|
|
|
|
Raises :exc:`HeaderError` if the buffer is invalid..
|
|
|
|
|
|
.. method:: TarInfo.fromtarfile(tarfile)
|
|
|
|
Read the next member from the :class:`TarFile` object *tarfile* and return it as
|
|
a :class:`TarInfo` object.
|
|
|
|
|
|
.. method:: TarInfo.tobuf(format=DEFAULT_FORMAT, encoding=ENCODING, errors='surrogateescape')
|
|
|
|
Create a string buffer from a :class:`TarInfo` object. For information on the
|
|
arguments see the constructor of the :class:`TarFile` class.
|
|
|
|
.. versionchanged:: 3.2
|
|
Use ``'surrogateescape'`` as the default for the *errors* argument.
|
|
|
|
|
|
A ``TarInfo`` object has the following public data attributes:
|
|
|
|
|
|
.. attribute:: TarInfo.name
|
|
|
|
Name of the archive member.
|
|
|
|
|
|
.. attribute:: TarInfo.size
|
|
|
|
Size in bytes.
|
|
|
|
|
|
.. attribute:: TarInfo.mtime
|
|
|
|
Time of last modification.
|
|
|
|
|
|
.. attribute:: TarInfo.mode
|
|
|
|
Permission bits.
|
|
|
|
|
|
.. attribute:: TarInfo.type
|
|
|
|
File type. *type* is usually one of these constants: :const:`REGTYPE`,
|
|
:const:`AREGTYPE`, :const:`LNKTYPE`, :const:`SYMTYPE`, :const:`DIRTYPE`,
|
|
:const:`FIFOTYPE`, :const:`CONTTYPE`, :const:`CHRTYPE`, :const:`BLKTYPE`,
|
|
:const:`GNUTYPE_SPARSE`. To determine the type of a :class:`TarInfo` object
|
|
more conveniently, use the ``is_*()`` methods below.
|
|
|
|
|
|
.. attribute:: TarInfo.linkname
|
|
|
|
Name of the target file name, which is only present in :class:`TarInfo` objects
|
|
of type :const:`LNKTYPE` and :const:`SYMTYPE`.
|
|
|
|
|
|
.. attribute:: TarInfo.uid
|
|
|
|
User ID of the user who originally stored this member.
|
|
|
|
|
|
.. attribute:: TarInfo.gid
|
|
|
|
Group ID of the user who originally stored this member.
|
|
|
|
|
|
.. attribute:: TarInfo.uname
|
|
|
|
User name.
|
|
|
|
|
|
.. attribute:: TarInfo.gname
|
|
|
|
Group name.
|
|
|
|
|
|
.. attribute:: TarInfo.pax_headers
|
|
|
|
A dictionary containing key-value pairs of an associated pax extended header.
|
|
|
|
|
|
A :class:`TarInfo` object also provides some convenient query methods:
|
|
|
|
|
|
.. method:: TarInfo.isfile()
|
|
|
|
Return :const:`True` if the :class:`Tarinfo` object is a regular file.
|
|
|
|
|
|
.. method:: TarInfo.isreg()
|
|
|
|
Same as :meth:`isfile`.
|
|
|
|
|
|
.. method:: TarInfo.isdir()
|
|
|
|
Return :const:`True` if it is a directory.
|
|
|
|
|
|
.. method:: TarInfo.issym()
|
|
|
|
Return :const:`True` if it is a symbolic link.
|
|
|
|
|
|
.. method:: TarInfo.islnk()
|
|
|
|
Return :const:`True` if it is a hard link.
|
|
|
|
|
|
.. method:: TarInfo.ischr()
|
|
|
|
Return :const:`True` if it is a character device.
|
|
|
|
|
|
.. method:: TarInfo.isblk()
|
|
|
|
Return :const:`True` if it is a block device.
|
|
|
|
|
|
.. method:: TarInfo.isfifo()
|
|
|
|
Return :const:`True` if it is a FIFO.
|
|
|
|
|
|
.. method:: TarInfo.isdev()
|
|
|
|
Return :const:`True` if it is one of character device, block device or FIFO.
|
|
|
|
|
|
.. _tar-examples:
|
|
|
|
Examples
|
|
--------
|
|
|
|
How to extract an entire tar archive to the current working directory::
|
|
|
|
import tarfile
|
|
tar = tarfile.open("sample.tar.gz")
|
|
tar.extractall()
|
|
tar.close()
|
|
|
|
How to extract a subset of a tar archive with :meth:`TarFile.extractall` using
|
|
a generator function instead of a list::
|
|
|
|
import os
|
|
import tarfile
|
|
|
|
def py_files(members):
|
|
for tarinfo in members:
|
|
if os.path.splitext(tarinfo.name)[1] == ".py":
|
|
yield tarinfo
|
|
|
|
tar = tarfile.open("sample.tar.gz")
|
|
tar.extractall(members=py_files(tar))
|
|
tar.close()
|
|
|
|
How to create an uncompressed tar archive from a list of filenames::
|
|
|
|
import tarfile
|
|
tar = tarfile.open("sample.tar", "w")
|
|
for name in ["foo", "bar", "quux"]:
|
|
tar.add(name)
|
|
tar.close()
|
|
|
|
The same example using the :keyword:`with` statement::
|
|
|
|
import tarfile
|
|
with tarfile.open("sample.tar", "w") as tar:
|
|
for name in ["foo", "bar", "quux"]:
|
|
tar.add(name)
|
|
|
|
How to read a gzip compressed tar archive and display some member information::
|
|
|
|
import tarfile
|
|
tar = tarfile.open("sample.tar.gz", "r:gz")
|
|
for tarinfo in tar:
|
|
print(tarinfo.name, "is", tarinfo.size, "bytes in size and is", end="")
|
|
if tarinfo.isreg():
|
|
print("a regular file.")
|
|
elif tarinfo.isdir():
|
|
print("a directory.")
|
|
else:
|
|
print("something else.")
|
|
tar.close()
|
|
|
|
How to create an archive and reset the user information using the *filter*
|
|
parameter in :meth:`TarFile.add`::
|
|
|
|
import tarfile
|
|
def reset(tarinfo):
|
|
tarinfo.uid = tarinfo.gid = 0
|
|
tarinfo.uname = tarinfo.gname = "root"
|
|
return tarinfo
|
|
tar = tarfile.open("sample.tar.gz", "w:gz")
|
|
tar.add("foo", filter=reset)
|
|
tar.close()
|
|
|
|
|
|
.. _tar-formats:
|
|
|
|
Supported tar formats
|
|
---------------------
|
|
|
|
There are three tar formats that can be created with the :mod:`tarfile` module:
|
|
|
|
* The POSIX.1-1988 ustar format (:const:`USTAR_FORMAT`). It supports filenames
|
|
up to a length of at best 256 characters and linknames up to 100 characters. The
|
|
maximum file size is 8 gigabytes. This is an old and limited but widely
|
|
supported format.
|
|
|
|
* The GNU tar format (:const:`GNU_FORMAT`). It supports long filenames and
|
|
linknames, files bigger than 8 gigabytes and sparse files. It is the de facto
|
|
standard on GNU/Linux systems. :mod:`tarfile` fully supports the GNU tar
|
|
extensions for long names, sparse file support is read-only.
|
|
|
|
* The POSIX.1-2001 pax format (:const:`PAX_FORMAT`). It is the most flexible
|
|
format with virtually no limits. It supports long filenames and linknames, large
|
|
files and stores pathnames in a portable way. However, not all tar
|
|
implementations today are able to handle pax archives properly.
|
|
|
|
The *pax* format is an extension to the existing *ustar* format. It uses extra
|
|
headers for information that cannot be stored otherwise. There are two flavours
|
|
of pax headers: Extended headers only affect the subsequent file header, global
|
|
headers are valid for the complete archive and affect all following files. All
|
|
the data in a pax header is encoded in *UTF-8* for portability reasons.
|
|
|
|
There are some more variants of the tar format which can be read, but not
|
|
created:
|
|
|
|
* The ancient V7 format. This is the first tar format from Unix Seventh Edition,
|
|
storing only regular files and directories. Names must not be longer than 100
|
|
characters, there is no user/group name information. Some archives have
|
|
miscalculated header checksums in case of fields with non-ASCII characters.
|
|
|
|
* The SunOS tar extended format. This format is a variant of the POSIX.1-2001
|
|
pax format, but is not compatible.
|
|
|
|
.. _tar-unicode:
|
|
|
|
Unicode issues
|
|
--------------
|
|
|
|
The tar format was originally conceived to make backups on tape drives with the
|
|
main focus on preserving file system information. Nowadays tar archives are
|
|
commonly used for file distribution and exchanging archives over networks. One
|
|
problem of the original format (which is the basis of all other formats) is
|
|
that there is no concept of supporting different character encodings. For
|
|
example, an ordinary tar archive created on a *UTF-8* system cannot be read
|
|
correctly on a *Latin-1* system if it contains non-*ASCII* characters. Textual
|
|
metadata (like filenames, linknames, user/group names) will appear damaged.
|
|
Unfortunately, there is no way to autodetect the encoding of an archive. The
|
|
pax format was designed to solve this problem. It stores non-ASCII metadata
|
|
using the universal character encoding *UTF-8*.
|
|
|
|
The details of character conversion in :mod:`tarfile` are controlled by the
|
|
*encoding* and *errors* keyword arguments of the :class:`TarFile` class.
|
|
|
|
*encoding* defines the character encoding to use for the metadata in the
|
|
archive. The default value is :func:`sys.getfilesystemencoding` or ``'ascii'``
|
|
as a fallback. Depending on whether the archive is read or written, the
|
|
metadata must be either decoded or encoded. If *encoding* is not set
|
|
appropriately, this conversion may fail.
|
|
|
|
The *errors* argument defines how characters are treated that cannot be
|
|
converted. Possible values are listed in section :ref:`codec-base-classes`.
|
|
The default scheme is ``'surrogateescape'`` which Python also uses for its
|
|
file system calls, see :ref:`os-filenames`.
|
|
|
|
In case of :const:`PAX_FORMAT` archives, *encoding* is generally not needed
|
|
because all the metadata is stored using *UTF-8*. *encoding* is only used in
|
|
the rare cases when binary pax headers are decoded or when strings with
|
|
surrogate characters are stored.
|
|
|