"tarfile" --- 讀取與寫入 tar 封存檔案
*************************************

**原始碼：**Lib/tarfile.py

======================================================================

The "tarfile" module makes it possible to read and write tar archives,
including those using gzip, bz2 and lzma compression. Use the
"zipfile" module to read or write ".zip" files, or the higher-level
functions in shutil.

Some facts and figures:

* reads and writes "gzip", "bz2" and "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.

在 3.3 版的變更: Added support for "lzma" compression.

在 3.12 版的變更: Archives are extracted using a filter, which makes
it possible to either limit surprising/dangerous features, or to
acknowledge that they are expected and the archive is fully trusted.
By default, archives are fully trusted, but this default is deprecated
and slated to change in Python 3.14.

tarfile.open(name=None, mode='r', fileobj=None, bufsize=10240, **kwargs)

   Return a "TarFile" object for the pathname *name*. For detailed
   information on "TarFile" objects and the keyword arguments that are
   allowed, see TarFile 物件.

   *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' 或 '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'" 或 "'x:'"    | Create a tarfile exclusively without          |
   |                    | compression. Raise a "FileExistsError"        |
   |                    | exception if it already exists.               |
   +--------------------+-----------------------------------------------+
   | "'x:gz'"           | Create a tarfile with gzip compression. Raise |
   |                    | a "FileExistsError" exception if it already   |
   |                    | exists.                                       |
   +--------------------+-----------------------------------------------+
   | "'x:bz2'"          | Create a tarfile with bzip2 compression.      |
   |                    | Raise a "FileExistsError" exception if it     |
   |                    | already exists.                               |
   +--------------------+-----------------------------------------------+
   | "'x:xz'"           | Create a tarfile with lzma compression. Raise |
   |                    | a "FileExistsError" exception if it already   |
   |                    | exists.                                       |
   +--------------------+-----------------------------------------------+
   | "'a' 或 'a:'"      | Open for appending with no compression. The   |
   |                    | file is created if it does not exist.         |
   +--------------------+-----------------------------------------------+
   | "'w' 或 '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, "ReadError" is raised. Use *mode* "'r'" to avoid this.  If
   a compression method is not supported, "CompressionError" is
   raised.

   If *fileobj* is specified, it is used as an alternative to a *file
   object* opened in binary mode for *name*. It is supposed to be at
   position 0.

   For modes "'w:gz'", "'x:gz'", "'w|gz'", "'w:bz2'", "'x:bz2'",
   "'w|bz2'", "tarfile.open()" accepts the keyword argument
   *compresslevel* (default "9") to specify the compression level of
   the file.

   For modes "'w:xz'" and "'x:xz'", "tarfile.open()" accepts the
   keyword argument *preset* to specify the compression level of the
   file.

   For special purposes, there is a second format for *mode*:
   "'filemode|[compression]'".  "tarfile.open()" will return a
   "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 "read()" or "write()" method (depending on
   the *mode*) that works with bytes. *bufsize* specifies the
   blocksize and defaults to "20 * 512" bytes. Use this variant in
   combination with e.g. "sys.stdin.buffer", a socket *file object* or
   a tape device. However, such a "TarFile" object is limited in that
   it does not allow random access, see 範例.  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.                                     |
   +---------------+----------------------------------------------+

   在 3.5 版的變更: The "'x'" (exclusive creation) mode was added.

   在 3.6 版的變更: The *name* parameter accepts a *path-like object*.

   在 3.12 版的變更: The *compresslevel* keyword argument also works
   for streams.

class tarfile.TarFile

   Class for reading and writing tar archives. Do not use this class
   directly: use "tarfile.open()" instead. See TarFile 物件.

tarfile.is_tarfile(name)

   Return "True" if *name* is a tar archive file, that the "tarfile"
   module can read. *name* may be a "str", file, or file-like object.

   在 3.9 版的變更: Support for file and file-like objects.

The "tarfile" module defines the following exceptions:

exception tarfile.TarError

   Base class for all "tarfile" exceptions.

exception tarfile.ReadError

   Is raised when a tar archive is opened, that either cannot be
   handled by the "tarfile" module or is somehow invalid.

exception tarfile.CompressionError

   Is raised when a compression method is not supported or when the
   data cannot be decoded properly.

exception tarfile.StreamError

   Is raised for the limitations that are typical for stream-like
   "TarFile" objects.

exception tarfile.ExtractError

   Is raised for *non-fatal* errors when using "TarFile.extract()",
   but only if "TarFile.errorlevel""== 2".

exception tarfile.HeaderError

   Is raised by "TarInfo.frombuf()" if the buffer it gets is invalid.

exception tarfile.FilterError

   Base class for members refused by filters.

   tarinfo

      Information about the member that the filter refused to extract,
      as TarInfo.

exception tarfile.AbsolutePathError

   Raised to refuse extracting a member with an absolute path.

exception tarfile.OutsideDestinationError

   Raised to refuse extracting a member outside the destination
   directory.

exception tarfile.SpecialFileError

   Raised to refuse extracting a special file (e.g. a device or pipe).

exception tarfile.AbsoluteLinkError

   Raised to refuse extracting a symbolic link with an absolute path.

exception tarfile.LinkOutsideDestinationError

   Raised to refuse extracting a symbolic link pointing outside the
   destination directory.

The following constants are available at the module level:

tarfile.ENCODING

   The default character encoding: "'utf-8'" on Windows, the value
   returned by "sys.getfilesystemencoding()" otherwise.

tarfile.REGTYPE
tarfile.AREGTYPE

   A regular file "type".

tarfile.LNKTYPE

   A link (inside tarfile) "type".

tarfile.SYMTYPE

   A symbolic link "type".

tarfile.CHRTYPE

   A character special device "type".

tarfile.BLKTYPE

   A block special device "type".

tarfile.DIRTYPE

   A directory "type".

tarfile.FIFOTYPE

   A FIFO special device "type".

tarfile.CONTTYPE

   A contiguous file "type".

tarfile.GNUTYPE_LONGNAME

   A GNU tar longname "type".

tarfile.GNUTYPE_LONGLINK

   A GNU tar longlink "type".

tarfile.GNUTYPE_SPARSE

   A GNU tar sparse file "type".

Each of the following constants defines a tar archive format that the
"tarfile" module is able to create. See section Supported tar formats
for details.

tarfile.USTAR_FORMAT

   POSIX.1-1988 (ustar) format.

tarfile.GNU_FORMAT

   GNU tar format.

tarfile.PAX_FORMAT

   POSIX.1-2001 (pax) format.

tarfile.DEFAULT_FORMAT

   The default format for creating archives. This is currently
   "PAX_FORMAT".

   在 3.8 版的變更: The default format for new archives was changed to
   "PAX_FORMAT" from "GNU_FORMAT".

也參考:

  "zipfile" 模組
     Documentation of the "zipfile" standard module.

  Archiving operations
     Documentation of the higher-level archiving facilities provided
     by the standard "shutil" module.

  GNU tar manual, Basic Tar Format
     Documentation for tar archive files, including GNU tar
     extensions.


TarFile 物件
============

The "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 "TarInfo" object, see TarInfo 物件 for details.

A "TarFile" object can be used as a context manager in a "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 範例 section for a use case.

在 3.2 版被加入: Added support for the context management protocol.

class tarfile.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=1, stream=False)

   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 *path-like
   object*. It can be omitted if *fileobj* is given. In this case, the
   file object's "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.

   備註:

     *fileobj* is not closed, when "TarFile" is closed.

   *format* controls the archive format for writing. It must be one of
   the constants "USTAR_FORMAT", "GNU_FORMAT" or "PAX_FORMAT" that are
   defined at module level. When reading, format will be automatically
   detected, even if different formats are present in a single
   archive.

   The *tarinfo* argument can be used to replace the default "TarInfo"
   class with a different one.

   If *dereference* is "False", add symbolic and hard links to the
   archive. If it is "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 "False", treat an empty block as the end of
   the archive. If it is "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".

   *errorlevel* controls how extraction errors are handled, see "the
   corresponding attribute".

   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 Unicode issues 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
   "PAX_FORMAT".

   If *stream* is set to "True" then while reading the archive info
   about files in the archive are not cached, saving memory.

   在 3.2 版的變更: Use "'surrogateescape'" as the default for the
   *errors* argument.

   在 3.5 版的變更: The "'x'" (exclusive creation) mode was added.

   在 3.6 版的變更: The *name* parameter accepts a *path-like object*.

   在 3.13 版的變更: 新增 *stream* 參數。

classmethod TarFile.open(...)

   Alternative constructor. The "tarfile.open()" function is actually
   a shortcut to this classmethod.

TarFile.getmember(name)

   Return a "TarInfo" object for member *name*. If *name* can not be
   found in the archive, "KeyError" is raised.

   備註:

     If a member occurs more than once in the archive, its last
     occurrence is assumed to be the most up-to-date version.

TarFile.getmembers()

   Return the members of the archive as a list of "TarInfo" objects.
   The list has the same order as the members in the archive.

TarFile.getnames()

   Return the members as a list of their names. It has the same order
   as the list returned by "getmembers()".

TarFile.list(verbose=True, *, members=None)

   Print a table of contents to "sys.stdout". If *verbose* is "False",
   only the names of the members are printed. If it is "True", output
   similar to that of **ls -l** is produced. If optional *members* is
   given, it must be a subset of the list returned by "getmembers()".

   在 3.5 版的變更: 新增 *members* 參數。

TarFile.next()

   Return the next member of the archive as a "TarInfo" object, when
   "TarFile" is opened for reading. Return "None" if there is no more
   available.

TarFile.extractall(path='.', members=None, *, numeric_owner=False, filter=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 "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 "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.

   The *filter* argument specifies how "members" are modified or
   rejected before extraction. See Extraction filters for details. It
   is recommended to set this explicitly depending on which *tar*
   features you need to support.

   警告:

     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 "".."".Set "filter='data'" to
     prevent the most dangerous security issues, and read the
     Extraction filters section for details.

   在 3.5 版的變更: 新增 *numeric_owner* 參數。

   在 3.6 版的變更: The *path* parameter accepts a *path-like object*.

   在 3.12 版的變更: 新增 *filter* 參數。

TarFile.extract(member, path='', set_attrs=True, *, numeric_owner=False, filter=None)

   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 "TarInfo"
   object. You can specify a different directory using *path*. *path*
   may be a *path-like object*. File attributes (owner, mtime, mode)
   are set unless *set_attrs* is false.

   The *numeric_owner* and *filter* arguments are the same as for
   "extractall()".

   備註:

     The "extract()" method does not take care of several extraction
     issues. In most cases you should consider using the
     "extractall()" method.

   警告:

     參閱 "extractall()" 的警告。Set "filter='data'" to prevent the
     most dangerous security issues, and read the Extraction filters
     section for details.

   在 3.2 版的變更: 增加 *set_attrs* 參數。

   在 3.5 版的變更: 新增 *numeric_owner* 參數。

   在 3.6 版的變更: The *path* parameter accepts a *path-like object*.

   在 3.12 版的變更: 新增 *filter* 參數。

TarFile.extractfile(member)

   Extract a member from the archive as a file object. *member* may be
   a filename or a "TarInfo" object. If *member* is a regular file or
   a link, an "io.BufferedReader" object is returned. For all other
   existing members, "None" is returned. If *member* does not appear
   in the archive, "KeyError" is raised.

   在 3.3 版的變更: Return an "io.BufferedReader" object.

   在 3.13 版的變更: The returned "io.BufferedReader" object has the
   "mode" attribute which is always equal to "'rb'".

TarFile.errorlevel: int

   If *errorlevel* is "0", errors are ignored when using
   "TarFile.extract()" and "TarFile.extractall()". Nevertheless, they
   appear as error messages in the debug output when *debug* is
   greater than 0. If "1" (the default), all *fatal* errors are raised
   as "OSError" or "FilterError" exceptions. If "2", all *non-fatal*
   errors are raised as "TarError" exceptions as well.

   Some exceptions, e.g. ones caused by wrong argument types or data
   corruption, are always raised.

   Custom extraction filters should raise "FilterError" for *fatal*
   errors and "ExtractError" for *non-fatal* ones.

   Note that when an exception is raised, the archive may be partially
   extracted. It is the user’s responsibility to clean up.

TarFile.extraction_filter

   在 3.12 版被加入.

   The extraction filter used as a default for the *filter* argument
   of "extract()" and "extractall()".

   The attribute may be "None" or a callable. String names are not
   allowed for this attribute, unlike the *filter* argument to
   "extract()".

   If "extraction_filter" is "None" (the default), calling an
   extraction method without a *filter* argument will raise a
   "DeprecationWarning", and fall back to the "fully_trusted" filter,
   whose dangerous behavior matches previous versions of Python.

   In Python 3.14+, leaving "extraction_filter=None" will cause
   extraction methods to use the "data" filter by default.

   The attribute may be set on instances or overridden in subclasses.
   It also is possible to set it on the "TarFile" class itself to set
   a global default, although, since it affects all uses of *tarfile*,
   it is best practice to only do so in top-level applications or
   "site configuration". To set a global default this way, a filter
   function needs to be wrapped in "staticmethod()" to prevent
   injection of a "self" argument.

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 "False". Recursion adds entries in sorted
   order. If *filter* is given, it should be a function that takes a
   "TarInfo" object argument and returns the changed "TarInfo" object.
   If it instead returns "None" the "TarInfo" object will be excluded
   from the archive. See 範例 for an example.

   在 3.2 版的變更: 新增 *filter* 參數。

   在 3.7 版的變更: Recursion adds entries in sorted order.

TarFile.addfile(tarinfo, fileobj=None)

   Add the "TarInfo" object *tarinfo* to the archive. If *tarinfo*
   represents a non zero-size regular file, the *fileobj* argument
   should be a *binary file*, and "tarinfo.size" bytes are read from
   it and added to the archive.  You can create "TarInfo" objects
   directly, or by using "gettarinfo()".

   在 3.13 版的變更: *fileobj* must be given for non-zero-sized
   regular files.

TarFile.gettarinfo(name=None, arcname=None, fileobj=None)

   Create a "TarInfo" object from the result of "os.stat()" or
   equivalent on an existing file.  The file is either named by
   *name*, or specified as a *file object* *fileobj* with a file
   descriptor. *name* may be a *path-like object*.  If given,
   *arcname* specifies an alternative name for the file in the
   archive, otherwise, the name is taken from *fileobj*’s "name"
   attribute, or the *name* argument.  The name should be a text
   string.

   You can modify some of the "TarInfo"’s attributes before you add it
   using "addfile()". If the file object is not an ordinary file
   object positioned at the beginning of the file, attributes such as
   "size" may need modifying.  This is the case for objects such as
   "GzipFile". The "name" may also be modified, in which case
   *arcname* could be a dummy string.

   在 3.6 版的變更: The *name* parameter accepts a *path-like object*.

TarFile.close()

   Close the "TarFile". In write mode, two finishing zero blocks are
   appended to the archive.

TarFile.pax_headers: dict

   A dictionary containing key-value pairs of pax global headers.


TarInfo 物件
============

A "TarInfo" object represents one member in a "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.

"TarInfo" objects are returned by "TarFile"'s methods "getmember()",
"getmembers()" and "gettarinfo()".

Modifying the objects returned by "getmember()" or "getmembers()" will
affect all subsequent operations on the archive. For cases where this
is unwanted, you can use "copy.copy()" or call the "replace()" method
to create a modified copy in one step.

Several attributes can be set to "None" to indicate that a piece of
metadata is unused or unknown. Different "TarInfo" methods handle
"None" differently:

* The "extract()" or "extractall()" methods will ignore the
  corresponding metadata, leaving it set to a default.

* "addfile()" will fail.

* "list()" will print a placeholder string.

class tarfile.TarInfo(name='')

   Create a "TarInfo" object.

classmethod TarInfo.frombuf(buf, encoding, errors)

   Create and return a "TarInfo" object from string buffer *buf*.

   Raises "HeaderError" if the buffer is invalid.

classmethod TarInfo.fromtarfile(tarfile)

   Read the next member from the "TarFile" object *tarfile* and return
   it as a "TarInfo" object.

TarInfo.tobuf(format=DEFAULT_FORMAT, encoding=ENCODING, errors='surrogateescape')

   Create a string buffer from a "TarInfo" object. For information on
   the arguments see the constructor of the "TarFile" class.

   在 3.2 版的變更: Use "'surrogateescape'" as the default for the
   *errors* argument.

A "TarInfo" object has the following public data attributes:

TarInfo.name: str

   Name of the archive member.

TarInfo.size: int

   Size in bytes.

TarInfo.mtime: int | float

   Time of last modification in seconds since the epoch, as in
   "os.stat_result.st_mtime".

   在 3.12 版的變更: Can be set to "None" for "extract()" and
   "extractall()", causing extraction to skip applying this attribute.

TarInfo.mode: int

   Permission bits, as for "os.chmod()".

   在 3.12 版的變更: Can be set to "None" for "extract()" and
   "extractall()", causing extraction to skip applying this attribute.

TarInfo.type

   File type.  *type* is usually one of these constants: "REGTYPE",
   "AREGTYPE", "LNKTYPE", "SYMTYPE", "DIRTYPE", "FIFOTYPE",
   "CONTTYPE", "CHRTYPE", "BLKTYPE", "GNUTYPE_SPARSE".  To determine
   the type of a "TarInfo" object more conveniently, use the "is*()"
   methods below.

TarInfo.linkname: str

   Name of the target file name, which is only present in "TarInfo"
   objects of type "LNKTYPE" and "SYMTYPE".

   For symbolic links ("SYMTYPE"), the *linkname* is relative to the
   directory that contains the link. For hard links ("LNKTYPE"), the
   *linkname* is relative to the root of the archive.

TarInfo.uid: int

   User ID of the user who originally stored this member.

   在 3.12 版的變更: Can be set to "None" for "extract()" and
   "extractall()", causing extraction to skip applying this attribute.

TarInfo.gid: int

   Group ID of the user who originally stored this member.

   在 3.12 版的變更: Can be set to "None" for "extract()" and
   "extractall()", causing extraction to skip applying this attribute.

TarInfo.uname: str

   User name.

   在 3.12 版的變更: Can be set to "None" for "extract()" and
   "extractall()", causing extraction to skip applying this attribute.

TarInfo.gname: str

   Group name.

   在 3.12 版的變更: Can be set to "None" for "extract()" and
   "extractall()", causing extraction to skip applying this attribute.

TarInfo.chksum: int

   Header checksum.

TarInfo.devmajor: int

   Device major number.

TarInfo.devminor: int

   Device minor number.

TarInfo.offset: int

   The tar header starts here.

TarInfo.offset_data: int

   The file's data starts here.

TarInfo.sparse

   Sparse member information.

TarInfo.pax_headers: dict

   A dictionary containing key-value pairs of an associated pax
   extended header.

TarInfo.replace(name=..., mtime=..., mode=..., linkname=..., uid=..., gid=..., uname=..., gname=..., deep=True)

   在 3.12 版被加入.

   Return a *new* copy of the "TarInfo" object with the given
   attributes changed. For example, to return a "TarInfo" with the
   group name set to "'staff'", use:

      new_tarinfo = old_tarinfo.replace(gname='staff')

   By default, a deep copy is made. If *deep* is false, the copy is
   shallow, i.e. "pax_headers" and any custom attributes are shared
   with the original "TarInfo" object.

A "TarInfo" object also provides some convenient query methods:

TarInfo.isfile()

   Return "True" if the "TarInfo" object is a regular file.

TarInfo.isreg()

   Same as "isfile()".

TarInfo.isdir()

   Return "True" if it is a directory.

TarInfo.issym()

   Return "True" if it is a symbolic link.

TarInfo.islnk()

   Return "True" if it is a hard link.

TarInfo.ischr()

   Return "True" if it is a character device.

TarInfo.isblk()

   Return "True" if it is a block device.

TarInfo.isfifo()

   Return "True" if it is a FIFO.

TarInfo.isdev()

   Return "True" if it is one of character device, block device or
   FIFO.


Extraction filters
==================

在 3.12 版被加入.

The *tar* format is designed to capture all details of a UNIX-like
filesystem, which makes it very powerful. Unfortunately, the features
make it easy to create tar files that have unintended -- and possibly
malicious -- effects when extracted. For example, extracting a tar
file can overwrite arbitrary files in various ways (e.g.  by using
absolute paths, ".." path components, or symlinks that affect later
members).

In most cases, the full functionality is not needed. Therefore,
*tarfile* supports extraction filters: a mechanism to limit
functionality, and thus mitigate some of the security issues.

也參考:

  **PEP 706**
     Contains further motivation and rationale behind the design.

The *filter* argument to "TarFile.extract()" or "extractall()" can be:

* the string "'fully_trusted'": Honor all metadata as specified in the
  archive. Should be used if the user trusts the archive completely,
  or implements their own complex verification.

* the string "'tar'": Honor most *tar*-specific features (i.e.
  features of UNIX-like filesystems), but block features that are very
  likely to be surprising or malicious. See "tar_filter()" for
  details.

* the string "'data'": Ignore or block most features specific to UNIX-
  like filesystems. Intended for extracting cross-platform data
  archives. See "data_filter()" for details.

* "None" (default): Use "TarFile.extraction_filter".

  If that is also "None" (the default), raise a "DeprecationWarning",
  and fall back to the "'fully_trusted'" filter, whose dangerous
  behavior matches previous versions of Python.

  In Python 3.14, the "'data'" filter will become the default instead.
  It's possible to switch earlier; see "TarFile.extraction_filter".

* A callable which will be called for each extracted member with a
  TarInfo describing the member and the destination path to where the
  archive is extracted (i.e. the same path is used for all members):

     filter(member: TarInfo, path: str, /) -> TarInfo | None

  The callable is called just before each member is extracted, so it
  can take the current state of the disk into account. It can:

  * return a "TarInfo" object which will be used instead of the
    metadata in the archive, or

  * return "None", in which case the member will be skipped, or

  * raise an exception to abort the operation or skip the member,
    depending on "errorlevel". Note that when extraction is aborted,
    "extractall()" may leave the archive partially extracted. It does
    not attempt to clean up.


Default named filters
---------------------

The pre-defined, named filters are available as functions, so they can
be reused in custom filters:

tarfile.fully_trusted_filter(member, path)

   Return *member* unchanged.

   This implements the "'fully_trusted'" filter.

tarfile.tar_filter(member, path)

   Implements the "'tar'" filter.

   * Strip leading slashes ("/" and "os.sep") from filenames.

   * Refuse to extract files with absolute paths (in case the name is
     absolute even after stripping slashes, e.g. "C:/foo" on Windows).
     This raises "AbsolutePathError".

   * Refuse to extract files whose absolute path (after following
     symlinks) would end up outside the destination. This raises
     "OutsideDestinationError".

   * Clear high mode bits (setuid, setgid, sticky) and group/other
     write bits ("S_IWGRP" | "S_IWOTH").

   Return the modified "TarInfo" member.

tarfile.data_filter(member, path)

   Implements the "'data'" filter. In addition to what "tar_filter"
   does:

   * Refuse to extract links (hard or soft) that link to absolute
     paths, or ones that link outside the destination.

     This raises "AbsoluteLinkError" or "LinkOutsideDestinationError".

     Note that such files are refused even on platforms that do not
     support symbolic links.

   * Refuse to extract device files (including pipes). This raises
     "SpecialFileError".

   * For regular files, including hard links:

     * Set the owner read and write permissions ("S_IRUSR" |
       "S_IWUSR").

     * Remove the group & other executable permission ("S_IXGRP" |
       "S_IXOTH") if the owner doesn’t have it ("S_IXUSR").

   * For other files (directories), set "mode" to "None", so that
     extraction methods skip applying permission bits.

   * Set user and group info ("uid", "gid", "uname", "gname") to
     "None", so that extraction methods skip setting it.

   Return the modified "TarInfo" member.


Filter errors
-------------

When a filter refuses to extract a file, it will raise an appropriate
exception, a subclass of "FilterError". This will abort the extraction
if "TarFile.errorlevel" is 1 or more. With "errorlevel=0" the error
will be logged and the member will be skipped, but extraction will
continue.


Hints for further verification
------------------------------

Even with "filter='data'", *tarfile* is not suited for extracting
untrusted files without prior inspection. Among other issues, the pre-
defined filters do not prevent denial-of-service attacks. Users should
do additional checks.

Here is an incomplete list of things to consider:

* Extract to a "new temporary directory" to prevent e.g. exploiting
  pre-existing links, and to make it easier to clean up after a failed
  extraction.

* When working with untrusted data, use external (e.g. OS-level)
  limits on disk, memory and CPU usage.

* Check filenames against an allow-list of characters (to filter out
  control characters, confusables, foreign path separators, etc.).

* Check that filenames have expected extensions (discouraging files
  that execute when you “click on them”, or extension-less files like
  Windows special device names).

* Limit the number of extracted files, total size of extracted data,
  filename length (including symlink length), and size of individual
  files.

* Check for files that would be shadowed on case-insensitive
  filesystems.

Also note that:

* Tar files may contain multiple versions of the same file. Later ones
  are expected to overwrite any earlier ones. This feature is crucial
  to allow updating tape archives, but can be abused maliciously.

* *tarfile* does not protect against issues with “live” data, e.g. an
  attacker tinkering with the destination (or source) directory while
  extraction (or archiving) is in progress.


Supporting older Python versions
--------------------------------

Extraction filters were added to Python 3.12, but may be backported to
older versions as security updates. To check whether the feature is
available, use e.g. "hasattr(tarfile, 'data_filter')" rather than
checking the Python version.

The following examples show how to support Python versions with and
without the feature. Note that setting "extraction_filter" will affect
any subsequent operations.

* Fully trusted archive:

     my_tarfile.extraction_filter = (lambda member, path: member)
     my_tarfile.extractall()

* Use the "'data'" filter if available, but revert to Python 3.11
  behavior ("'fully_trusted'") if this feature is not available:

     my_tarfile.extraction_filter = getattr(tarfile, 'data_filter',
                                            (lambda member, path: member))
     my_tarfile.extractall()

* Use the "'data'" filter; *fail* if it is not available:

     my_tarfile.extractall(filter=tarfile.data_filter)

  或：

     my_tarfile.extraction_filter = tarfile.data_filter
     my_tarfile.extractall()

* Use the "'data'" filter; *warn* if it is not available:

     if hasattr(tarfile, 'data_filter'):
         my_tarfile.extractall(filter='data')
     else:
         # remove this when no longer needed
         warn_the_user('Extracting may be unsafe; consider updating Python')
         my_tarfile.extractall()


Stateful extraction filter example
----------------------------------

While *tarfile*'s extraction methods take a simple *filter* callable,
custom filters may be more complex objects with an internal state. It
may be useful to write these as context managers, to be used like
this:

   with StatefulFilter() as filter_func:
       tar.extractall(path, filter=filter_func)

Such a filter can be written as, for example:

   class StatefulFilter:
       def __init__(self):
           self.file_count = 0

       def __enter__(self):
           return self

       def __call__(self, member, path):
           self.file_count += 1
           return member

       def __exit__(self, *exc_info):
           print(f'{self.file_count} files extracted')


Command-Line Interface
======================

在 3.4 版被加入.

The "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
"-c" option and then list the filename(s) that should be included:

   $ python -m tarfile -c monty.tar  spam.txt eggs.txt

Passing a directory is also acceptable:

   $ python -m tarfile -c monty.tar life-of-brian_1979/

If you want to extract a tar archive into the current directory, use
the "-e" option:

   $ python -m tarfile -e monty.tar

You can also extract a tar archive into a different directory by
passing the directory's name:

   $ python -m tarfile -e monty.tar  other-dir/

For a list of the files in a tar archive, use the "-l" option:

   $ python -m tarfile -l monty.tar


命令列選項
----------

-l <tarfile>
--list <tarfile>

   List files in a tarfile.

-c <tarfile> <source1> ... <sourceN>
--create <tarfile> <source1> ... <sourceN>

   Create tarfile from source files.

-e <tarfile> [<output_dir>]
--extract <tarfile> [<output_dir>]

   Extract tarfile into the current directory if *output_dir* is not
   specified.

-t <tarfile>
--test <tarfile>

   Test whether the tarfile is valid or not.

-v, --verbose

   Verbose output.

--filter <filtername>

   Specifies the *filter* for "--extract". See Extraction filters for
   details. Only string names are accepted (that is, "fully_trusted",
   "tar", and "data").


範例
====

How to extract an entire tar archive to the current working directory:

   import tarfile
   tar = tarfile.open("sample.tar.gz")
   tar.extractall(filter='data')
   tar.close()

How to extract a subset of a tar archive with "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 "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 "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()


Supported tar formats
=====================

There are three tar formats that can be created with the "tarfile"
module:

* The POSIX.1-1988 ustar format ("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 ("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. "tarfile" fully supports the
  GNU tar extensions for long names, sparse file support is read-only.

* The POSIX.1-2001 pax format ("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.
  Modern tar implementations, including GNU tar, bsdtar/libarchive and
  star, fully support extended *pax* features; some old or
  unmaintained libraries may not, but should treat *pax* archives as
  if they were in the universally supported *ustar* format. It is the
  current default format for new archives.

  It extends the existing *ustar* format with 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.


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 "tarfile" are controlled by the
*encoding* and *errors* keyword arguments of the "TarFile" class.

*encoding* defines the character encoding to use for the metadata in
the archive. The default value is "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 Error Handlers.
The default scheme is "'surrogateescape'" which Python also uses for
its file system calls, see File Names, Command Line Arguments, and
Environment Variables.

For "PAX_FORMAT" archives (the default), *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.
