資料壓縮和歸檔(三)、tarfile

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.

Changed in version 3.3: Added support for

lzma

compression.

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 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 'x:'	Create a tarfile exclusively without compression. Raise an FileExistsError exception if it already exists.
'x:gz'	Create a tarfile with gzip compression. Raise an FileExistsError exception if it already exists.
'x:bz2'	Create a tarfile with bzip2 compression. Raise an FileExistsError exception if it already exists.
'x:xz'	Create a tarfile with lzma compression. Raise an 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'

'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'

'r:gz'

'w:bz2'

'r:bz2'

'x:gz'

'x:bz2'

tarfile.open()

accepts the keyword argument compresslevel (default

) 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()

write()

method (depending on the mode). bufsize specifies the blocksize and defaults to

20 * 512

bytes. Use this variant in combination with e.g.

sys.stdin

, a socket file object or a tape device. However, such a

TarFile

object is limited in that it does not allow random access, see 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.

Changed in version 3.5: The

'x'

(exclusive creation) mode was added.

Changed in version 3.6: The name parameter accepts a path-like object.

class

tarfile.TarFile

Class for reading and writing tar archives. Do not use this class directly: use

tarfile.open()

instead. See TarFile Objects.

tarfile.is_tarfile

(name)

Return

True

if name is a tar archive file, that the

tarfile

module can read.

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.

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

GNU_FORMAT

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.

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 Examples section for a use case.

New in version 3.2: 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.

Note

fileobj is not closed, when

TarFile

is closed.

format controls the archive format. It must be one of the constants

USTAR_FORMAT

GNU_FORMAT

PAX_FORMAT

that are defined at module level.

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

(no debug messages) up to

(all debug messages). The messages are written to

sys.stderr

If errorlevel is

, all errors are ignored when using

TarFile.extract()

. Nevertheless, they appear as error messages in the debug output, when debugging is enabled. If

, all fatal errors are raised as

OSError

exceptions. If

, 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

Changed in version 3.2: Use

'surrogateescape'

as the default for the errors argument.

Changed in version 3.5: The

'x'

(exclusive creation) mode was added.

Changed in version 3.6: The name parameter accepts a 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.

Note

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()

Changed in version 3.5: 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.

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

".."

Changed in version 3.5: Added the numeric_owner parameter.

Changed in version 3.6: The path parameter accepts a 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.

Note

The

extract()

method does not take care of several extraction issues. In most cases you should consider using the

extractall()

method.

Warning

See the warning for

extractall()

Changed in version 3.2: Added the set_attrs parameter.

Changed in version 3.5: Added the numeric_owner parameter.

Changed in version 3.6: The path parameter accepts a 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.

Changed in version 3.3: 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 Examples for an example.

Changed in version 3.2: Added the filter parameter.

Changed in version 3.7: 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.

Changed in version 3.6: 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

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

TarInfo Objects

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.

Changed in version 3.2: Use

'surrogateescape'

as the default for the errors argument.

TarInfo

object has the following public data attributes:

TarInfo.name

Name of the archive member.

TarInfo.size

Size in bytes.

TarInfo.mtime

Time of last modification.

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.

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.

Command-Line Interface

New in version 3.4.

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

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Passing a directory is also acceptable:

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

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If you want to extract a tar archive into the current directory, use the

-e

option:

$ python -m tarfile -e monty.tar

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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/

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For a list of the files in a tar archive, use the

-l

option:

$ python -m tarfile -l monty.tar

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Command-line options

-l <tarfile>

--list <tarfile>

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List files in a tarfile.

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

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

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Create tarfile from source files.

-e <tarfile> [<output_dir>]

--extract <tarfile> [<output_dir>]

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

-t <tarfile>

--test <tarfile>

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Test whether the tarfile is valid or not.

-v, --verbose

Verbose output.

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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()

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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()

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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()

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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)

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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()

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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()

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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. 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.

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()

'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.

In case of

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.