13.6. tarfile — 读写 tar 存档文件 ¶

13.6.1. TarFile Objects ¶

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 了解细节。

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 范例 section for a use case.

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 可以是 像路径对象 . It can be omitted if fileobj is given. In this case, the file object’s name attribute is used if it exists.

mode 是 '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.

若 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.

注意

fileobj is not closed, when TarFile is closed.

format controls the archive format. It must be one of the constants USTAR_FORMAT , GNU_FORMAT or PAX_FORMAT that are defined at module level.

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

若 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.

若 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 .

若 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.

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.

pax_headers argument is an optional dictionary of strings which will be added as a pax global header if format is PAX_FORMAT .

3.2 版改变： 使用 'surrogateescape' as the default for the errors 自变量。

3.5 版改变： 'x' (exclusive creation) mode was added.

3.6 版改变： name parameter accepts a 像路径对象 .

classmethod TarFile. open ( ... ) ¶

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

TarFile. getmember ( name ) ¶

返回 TarInfo object for member name 。若 name can not be found in the archive, KeyError 被引发。

注意

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 。若 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() .

3.5 版改变： 添加 members 参数。

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.

若 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 ".." .

3.5 版改变： 添加 numeric_owner 参数。

3.6 版改变： path parameter accepts a 像路径对象 .

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 可以是 像路径对象 . File attributes (owner, mtime, mode) are set unless set_attrs 为 False。

若 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.

注意

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

警告

See the warning for extractall() .

3.2 版改变： 添加 set_attrs 参数。

3.5 版改变： 添加 numeric_owner 参数。

3.6 版改变： path parameter accepts a 像路径对象 .

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 被返回。

3.3 版改变： 返回 io.BufferedReader 对象。

TarFile. add ( name , arcname=None , recursive=True , exclude=None , * , filter=None ) ¶

添加文件 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 。若 exclude is given, it must be a function that takes one filename argument and returns a boolean value. Depending on this value the respective file is either excluded ( True ) or added ( False )。若 filter is specified it must be a keyword argument. 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 范例 范例。

3.2 版改变： 添加 filter 参数。

从 3.2 版起弃用： exclude parameter is deprecated, please use the filter parameter instead.

TarFile. addfile ( tarinfo , fileobj=None ) ¶

Add the TarInfo object tarinfo to the archive. If fileobj is given, it should be a 二进制文件 ，和 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 ) ¶

创建 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 文件对象 fileobj with a file descriptor. name 可以是 像路径对象 . 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 . name may also be modified, in which case arcname could be a dummy string.

3.6 版改变： name parameter accepts a 像路径对象 .

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.

13.6.2. 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="" ) ¶

创建 TarInfo 对象。

classmethod TarInfo. frombuf ( buf , encoding , errors ) ¶

Create and return a TarInfo object from string buffer buf .

引发 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 对象。

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 类。

3.2 版改变： 使用 'surrogateescape' as the default for the errors 自变量。

A 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 ¶

文件类型。 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 ( ) ¶

返回 True 若 Tarinfo object is a regular file.

TarInfo. isreg ( ) ¶

如同 isfile() .

TarInfo. isdir ( ) ¶

返回 True if it is a directory.

TarInfo. issym ( ) ¶

返回 True if it is a symbolic link.

TarInfo. islnk ( ) ¶

返回 True if it is a hard link.

TarInfo. ischr ( ) ¶

返回 True if it is a character device.

TarInfo. isblk ( ) ¶

返回 True if it is a block device.

TarInfo. isfifo ( ) ¶

返回 True if it is a FIFO.

TarInfo. isdev ( ) ¶

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

13.6.3. Command-Line Interface ¶

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
								

13.6.4. Examples ¶

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

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

How to extract a subset of a tar archive with 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 语句：

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()
								

13.6.5. Supported tar formats ¶

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

• 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.

  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.

13.6.6. 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 类。

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.

errors argument defines how characters are treated that cannot be converted. Possible values are listed in section 错误处理程序 . 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.