:mod:`tarfile` --- Read and write tar archive files =================================================== .. module:: tarfile :synopsis: Read and write tar-format archive files. .. moduleauthor:: Lars Gustäbel .. sectionauthor:: Lars Gustäbel **Source code:** :source:`Lib/tarfile.py` -------------- The :mod:`tarfile` module makes it possible to read and write tar archives, including those using gzip, bz2 and lzma compression. Use the :mod:`zipfile` module to read or write :file:`.zip` files, or the higher-level functions in :ref:`shutil `. Some facts and figures: * reads and writes :mod:`gzip`, :mod:`bz2` and :mod:`lzma` compressed archives if the respective modules are available. * 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 all variants of the *sparse* extension including restoration of sparse files. * 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. .. versionchanged:: 3.3 Added support for :mod:`lzma` compression. .. 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. | +------------------+---------------------------------------------+ | ``'r:xz'`` | Open for reading with lzma compression. | +------------------+---------------------------------------------+ | ``'x'`` or | Create a tarfile exclusively without | | ``'x:'`` | compression. | | | Raise an :exc:`FileExistsError` exception | | | if it already exists. | +------------------+---------------------------------------------+ | ``'x:gz'`` | Create a tarfile with gzip compression. | | | Raise an :exc:`FileExistsError` exception | | | if it already exists. | +------------------+---------------------------------------------+ | ``'x:bz2'`` | Create a tarfile with bzip2 compression. | | | Raise an :exc:`FileExistsError` exception | | | if it already exists. | +------------------+---------------------------------------------+ | ``'x:xz'`` | Create a tarfile with lzma compression. | | | Raise an :exc:`FileExistsError` exception | | | if it already exists. | +------------------+---------------------------------------------+ | ``'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. | +------------------+---------------------------------------------+ | ``'w:xz'`` | Open for lzma compressed writing. | +------------------+---------------------------------------------+ Note that ``'a:gz'``, ``'a:bz2'`` or ``'a:xz'`` 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 :term:`file object` opened in binary mode for *name*. It is supposed to be at position 0. For modes ``'w:gz'``, ``'r:gz'``, ``'w:bz2'``, ``'r:bz2'``, ``'x:gz'``, ``'x:bz2'``, :func:`tarfile.open` accepts the keyword argument *compresslevel* (default ``9``) to specify the compression level of the file. 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 :term:`file object` or a tape device. However, such a :class:`TarFile` object is limited in that it does not allow random access, 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. | +-------------+--------------------------------------------+ | ``'r|xz'`` | Open an lzma compressed *stream* for | | | reading. | +-------------+--------------------------------------------+ | ``'w|'`` | Open an uncompressed *stream* for writing. | +-------------+--------------------------------------------+ | ``'w|gz'`` | Open a gzip compressed *stream* for | | | writing. | +-------------+--------------------------------------------+ | ``'w|bz2'`` | Open a bzip2 compressed *stream* for | | | writing. | +-------------+--------------------------------------------+ | ``'w|xz'`` | Open an lzma compressed *stream* for | | | writing. | +-------------+--------------------------------------------+ .. versionchanged:: 3.5 The ``'x'`` (exclusive creation) mode was added. .. versionchanged:: 3.6 The *name* parameter accepts a :term:`path-like object`. .. class:: TarFile Class for reading and writing tar archives. Do not use this class directly: 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. The following constants are available at the module level: .. data:: ENCODING The default character encoding: ``'utf-8'`` on Windows, the value returned by :func:`sys.getfilesystemencoding` otherwise. 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`. .. seealso:: Module :mod:`zipfile` Documentation of the :mod:`zipfile` standard module. :ref:`archiving-operations` Documentation of the higher-level archiving facilities provided by the standard :mod:`shutil` module. `GNU tar manual, Basic Tar Format `_ 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 management 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. *name* may be a :term:`path-like object`. 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, ``'w'`` to create a new file overwriting an existing one, or ``'x'`` to create a new file only if it does not already exist. 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` 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. 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`. .. versionchanged:: 3.2 Use ``'surrogateescape'`` as the default for the *errors* argument. .. versionchanged:: 3.5 The ``'x'`` (exclusive creation) mode was added. .. versionchanged:: 3.6 The *name* parameter accepts a :term:`path-like object`. .. classmethod:: 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, *, members=None) 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. If optional *members* is given, it must be a subset of the list returned by :meth:`getmembers`. .. versionchanged:: 3.5 Added the *members* parameter. .. 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, *, numeric_owner=False) 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. If *numeric_owner* is :const:`True`, the uid and gid numbers from the tarfile are used to set the owner/group for the extracted files. Otherwise, the named values from the tarfile are used. .. 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 ``".."``. .. versionchanged:: 3.5 Added the *numeric_owner* parameter. .. versionchanged:: 3.6 The *path* parameter accepts a :term:`path-like object`. .. method:: TarFile.extract(member, path="", set_attrs=True, *, numeric_owner=False) 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*. *path* may be a :term:`path-like object`. File attributes (owner, mtime, mode) are set unless *set_attrs* is false. If *numeric_owner* is :const:`True`, the uid and gid numbers from the tarfile are used to set the owner/group for the extracted files. Otherwise, the named values from the tarfile are used. .. 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`. .. versionchanged:: 3.2 Added the *set_attrs* parameter. .. versionchanged:: 3.5 Added the *numeric_owner* parameter. .. versionchanged:: 3.6 The *path* parameter accepts a :term:`path-like object`. .. 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 or a link, an :class:`io.BufferedReader` object is returned. Otherwise, :const:`None` is returned. .. versionchanged:: 3.3 Return an :class:`io.BufferedReader` object. .. method:: TarFile.add(name, arcname=None, recursive=True, *, 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 *filter* is given, it should 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. .. method:: TarFile.addfile(tarinfo, fileobj=None) Add the :class:`TarInfo` object *tarinfo* to the archive. If *fileobj* is given, it should be a :term:`binary file`, and ``tarinfo.size`` bytes are read from it and added to the archive. You can create :class:`TarInfo` objects directly, or by using :meth:`gettarinfo`. .. method:: TarFile.gettarinfo(name=None, arcname=None, fileobj=None) Create a :class:`TarInfo` object from the result of :func:`os.stat` or equivalent on an existing file. The file is either named by *name*, or specified as a :term:`file object` *fileobj* with a file descriptor. *name* may be a :term:`path-like object`. If given, *arcname* specifies an alternative name for the file in the archive, otherwise, the name is taken from *fileobj*’s :attr:`~io.FileIO.name` attribute, or the *name* argument. The name should be a text string. You can modify some of the :class:`TarInfo`’s attributes before you add it using :meth:`addfile`. If the file object is not an ordinary file object positioned at the beginning of the file, attributes such as :attr:`~TarInfo.size` may need modifying. This is the case for objects such as :class:`~gzip.GzipFile`. The :attr:`~TarInfo.name` may also be modified, in which case *arcname* could be a dummy string. .. versionchanged:: 3.6 The *name* parameter accepts a :term:`path-like object`. .. 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. .. classmethod:: TarInfo.frombuf(buf, encoding, errors) Create and return a :class:`TarInfo` object from string buffer *buf*. Raises :exc:`HeaderError` if the buffer is invalid. .. classmethod:: 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. .. _tarfile-commandline: .. program:: tarfile Command-Line Interface ---------------------- .. versionadded:: 3.4 The :mod:`tarfile` module provides a simple command-line interface to interact with tar archives. If you want to create a new tar archive, specify its name after the :option:`-c` option and then list the filename(s) that should be included: .. code-block:: shell-session $ python -m tarfile -c monty.tar spam.txt eggs.txt Passing a directory is also acceptable: .. code-block:: shell-session $ python -m tarfile -c monty.tar life-of-brian_1979/ If you want to extract a tar archive into the current directory, use the :option:`-e` option: .. code-block:: shell-session $ python -m tarfile -e monty.tar You can also extract a tar archive into a different directory by passing the directory's name: .. code-block:: shell-session $ python -m tarfile -e monty.tar other-dir/ For a list of the files in a tar archive, use the :option:`-l` option: .. code-block:: shell-session $ python -m tarfile -l monty.tar Command-line options ~~~~~~~~~~~~~~~~~~~~ .. cmdoption:: -l --list List files in a tarfile. .. cmdoption:: -c ... --create ... Create tarfile from source files. .. cmdoption:: -e [] --extract [] Extract tarfile into the current directory if *output_dir* is not specified. .. cmdoption:: -t --test Test whether the tarfile is valid or not. .. cmdoption:: -v, --verbose Verbose output. .. _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 GiB. 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 GiB 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:`error-handlers`. 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.