"tarfile" --- 读写tar归档文件
*****************************

**源代码:** Lib/tarfile.py

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

"tarfile" 模块可以用来读写 tar 归档，包括使用 gzip, bz2 和 lzma 压缩的
归档。 请使用 "zipfile" 模块来读写 ".zip" 文件，或者使用 shutil 的高层
级函数。

一些事实和数字:

* 读写 "gzip", "bz2" 和 "lzma" 解压的归档要求相应的模块可用。

* 支持读取 / 写入 POSIX.1-1988 (ustar) 格式。

* 对 GNU tar 格式的读/写支持，包括 *longname* 和 *longlink* 扩展，对所
  有种类 *sparse* 扩展的只读支持，包括 sparse 文件的恢复。

* 对 POSIX.1-2001 (pax) 格式的读/写支持。

* 处理目录、正常文件、硬链接、符号链接、fifo 管道、字符设备和块设备，
  并且能够获取和恢复文件信息例如时间戳、访问权限和所有者等。

在 3.3 版更改: 添加了对 "lzma" 压缩的支持。

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

   针对路径名 *name* 返回 "TarFile" 对象。 有关 "TarFile" 对象以及所允
   许的关键字参数的详细信息请参阅 TarFile Objects。

   *mode* 必须是 "'filemode[:compression]'" 形式的字符串，其默认值为
   "'r'"。 以下是模式组合的完整列表:

   +--------------------+-----------------------------------------------+
   | 模式               | 动作                                          |
   |====================|===============================================|
   | "'r' or 'r:*'"     | 打开和读取使用透明压缩（推荐）。              |
   +--------------------+-----------------------------------------------+
   | "'r:'"             | 打开和读取不使用压缩。                        |
   +--------------------+-----------------------------------------------+
   | "'r:gz'"           | 打开和读取使用gzip 压缩。                     |
   +--------------------+-----------------------------------------------+
   | "'r:bz2'"          | 打开和读取使用bzip2 压缩。                    |
   +--------------------+-----------------------------------------------+
   | "'r:xz'"           | 打开和读取使用lzma 压缩。                     |
   +--------------------+-----------------------------------------------+
   | "'x'" 或 "'x:'"    | 创建tarfile不进行压缩。如果文件已经存在，则抛 |
   |                    | 出 "FileExistsError" 异常。                   |
   +--------------------+-----------------------------------------------+
   | "'x:gz'"           | 使用gzip压缩创建tarfile。如果文件已经存在，则 |
   |                    | 抛出 "FileExistsError" 异常。                 |
   +--------------------+-----------------------------------------------+
   | "'x:bz2'"          | 使用bzip2 压缩创建tarfile。如果文件已经存在， |
   |                    | 则抛出 "FileExistsError" 异常。               |
   +--------------------+-----------------------------------------------+
   | "'x:xz'"           | 使用lzma 压缩创建tarfile。如果文件已经存在，  |
   |                    | 则抛出 "FileExistsError" 异常。               |
   +--------------------+-----------------------------------------------+
   | "'a' or 'a:'"      | 打开以便在没有压缩的情况下追加。如果文件不存  |
   |                    | 在，则创建该文件。                            |
   +--------------------+-----------------------------------------------+
   | "'w' or 'w:'"      | 打开用于未压缩的写入。                        |
   +--------------------+-----------------------------------------------+
   | "'w:gz'"           | 打开用于 gzip 压缩的写入。                    |
   +--------------------+-----------------------------------------------+
   | "'w:bz2'"          | 打开用于 bzip2 压缩的写入。                   |
   +--------------------+-----------------------------------------------+
   | "'w:xz'"           | 打开用于 lzma 压缩的写入。                    |
   +--------------------+-----------------------------------------------+

   请注意 "'a:gz'", "'a:bz2'" 或 "'a:xz'" 是不可能的组合。 如果 *mode*
   不适用于打开特定（压缩的）文件用于读取，则会引发 "ReadError"。 请使
   用 *mode* "'r'" 来避免这种情况。 如果某种压缩方法不受支持，则会引发
   "CompressionError"。

   如果指定了 *fileobj*，它会被用作对应于 *name* 的以二进制模式打开的
   *file object* 的替代。 它会被设定为处在位置 0。

   对于 "'w:gz'", "'r:gz'", "'w:bz2'", "'r:bz2'", "'x:gz'", "'x:bz2'"
   等模式，"tarfile.open()" 接受关键字参数 *compresslevel* (默认值为
   "9") 来指定文件的压缩等级。

   针对特殊的目的，还存在第二种 *mode* 格式:
   "'filemode|[compression]'"。 "tarfile.open()" 将返回一个将其数据作
   为数据块流来处理的 "TarFile" 对象。 对此文件将不能执行随机查找。 如
   果给定了 *fileobj*，它可以是任何具有 "read()" 或 "write()" 方法 (由
   *mode* 确定) 的对象。 *bufsize* 指定块大小，默认值为 "20 * 512" 字
   节。 可与此格式组合使用的有 "sys.stdin", 套接字 *file object* 或磁
   带设备等。 但是，对于这样的 "TarFile" 对象存在不允许随机访问的限制
   ，参见 示例。 目前可用的模式如下:

   +---------------+----------------------------------------------+
   | 模式          | 动作                                         |
   |===============|==============================================|
   | "'r|*'"       | 打开 tar 块的 *流* 以进行透明压缩读取。      |
   +---------------+----------------------------------------------+
   | "'r|'"        | 打开一个未压缩的 tar 块的 *stream* 用于读取  |
   |               | 。                                           |
   +---------------+----------------------------------------------+
   | "'r|gz'"      | 打开一个 gzip 压缩的 *stream* 用于读取。     |
   +---------------+----------------------------------------------+
   | "'r|bz2'"     | 打开一个 bzip2 压缩的 *stream* 用于读取。    |
   +---------------+----------------------------------------------+
   | "'r|xz'"      | 打开一个 lzma 压缩 *stream* 用于读取。       |
   +---------------+----------------------------------------------+
   | "'w|'"        | 打开一个未压缩的 *stream* 用于写入。         |
   +---------------+----------------------------------------------+
   | "'w|gz'"      | 打开一个 gzip 压缩的 *stream* 用于写入。     |
   +---------------+----------------------------------------------+
   | "'w|bz2'"     | 打开一个 bzip2 压缩的 *stream* 用于写入。    |
   +---------------+----------------------------------------------+
   | "'w|xz'"      | 打开一个 lzma 压缩的 *stream* 用于写入。     |
   +---------------+----------------------------------------------+

   在 3.5 版更改: 添加了 "'x'" (仅创建) 模式。

   在 3.6 版更改: *name* 形参接受一个 *path-like object*。

class tarfile.TarFile

   用于读取和写入 tar 归档的类。 请不要直接使用这个类：而要使用
   "tarfile.open()"。 参见 TarFile Objects。

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 版更改: Support for file and file-like objects.

"tarfile" 模块定义了以下异常:

exception tarfile.TarError

   所有 "tarfile" 异常的基类。

exception tarfile.ReadError

   当一个不能被 "tarfile" 模块处理或者因某种原因而无效的 tar 归档被打
   开时将被引发。

exception tarfile.CompressionError

   当一个压缩方法不受支持或者当数据无法被正确解码时将被引发。

exception tarfile.StreamError

   当达到流式 "TarFile" 对象的典型限制时将被引发。

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.

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.

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 版更改: The default format for new archives was changed to
   "PAX_FORMAT" from "GNU_FORMAT".

参见:

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

  归档操作
     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 Objects
===============

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 Objects 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 示例 section for a use case.

3.2 新版功能: 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=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 *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.

   注解:

     *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".

   If *errorlevel* is "0", all errors are ignored when using
   "TarFile.extract()". Nevertheless, they appear as error messages in
   the debug output, when debugging is enabled.  If "1", all *fatal*
   errors are raised as "OSError" exceptions. If "2", all *non-fatal*
   errors are raised as "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 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".

   在 3.2 版更改: Use "'surrogateescape'" as the default for the
   *errors* argument.

   在 3.5 版更改: 添加了 "'x'" (仅创建) 模式。

   在 3.6 版更改: *name* 形参接受一个 *path-like object*。

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.

   注解:

     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 版更改: Added the *members* parameter.

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)

   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.

   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 "".."".

   在 3.5 版更改: Added the *numeric_owner* parameter.

   在 3.6 版更改: *path* 形参接受一个 *path-like object*。

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 "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.

   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.

   注解:

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

   警告:

     See the warning for "extractall()".

   在 3.2 版更改: Added the *set_attrs* parameter.

   在 3.5 版更改: Added the *numeric_owner* parameter.

   在 3.6 版更改: *path* 形参接受一个 *path-like object*。

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. Otherwise,
   "None" is returned.

   在 3.3 版更改: Return an "io.BufferedReader" object.

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 示例 for an example.

   在 3.2 版更改: Added the *filter* parameter.

   在 3.7 版更改: Recursion adds entries in sorted order.

TarFile.addfile(tarinfo, fileobj=None)

   Add the "TarInfo" object *tarinfo* to the archive. If *fileobj* is
   given, it 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()".

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 版更改: *name* 形参接受一个 *path-like object*。

TarFile.close()

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

TarFile.pax_headers

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


TarInfo Objects
===============

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()".

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 版更改: Use "'surrogateescape'" as the default for the
   *errors* argument.

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

TarInfo.name

   Name of the archive member.

TarInfo.size

   Size in bytes.

TarInfo.mtime

   上次修改的时间。

TarInfo.mode

   Permission bits.

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

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

TarInfo.uid

   User ID of the user who originally stored this member.

TarInfo.gid

   Group ID of the user who originally stored this member.

TarInfo.uname

   User name.

TarInfo.gname

   Group name.

TarInfo.pax_headers

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

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.


命令行界面
==========

3.4 新版功能.

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

传入一个字典也是可接受的:

   $ 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


命令行选项
----------

-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.


示例
====

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 "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 错误处理方案. The
default scheme is "'surrogateescape'" which Python also uses for its
file system calls, see 文件名，命令行参数，以及环境变量。.

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.
