5. tarfile — Read and write tar archive files¶

5.1. 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 Examples 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=None, pax_headers=None, debug=0, errorlevel=0)[source]

All following arguments are optional and can be accessed as instance attributes as well.

name is the pathname of the archive. 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 or 'w' to create a new file overwriting an existing one.

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 or PAX_FORMAT that are defined at module level.

New in version 2.6.

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

New in version 2.6.

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 or IOError exceptions. If 2, all non-fatal errors are raised as TarError exceptions as well.

The encoding and errors arguments control the way strings are converted to unicode objects and vice versa. The default settings will work for most users. See section Unicode issues for in-depth information.

New in version 2.6.

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

New in version 2.6.

classmethod TarFile.open(...)[source]¶

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

TarFile.getmember(name)[source]¶

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()[source]¶

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()[source]¶

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

TarFile.list(verbose=True)[source]¶

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.

TarFile.next()[source]¶

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)[source]¶

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.

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 "..".

New in version 2.5.

TarFile.extract(member, path="")[source]¶

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.

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().

TarFile.extractfile(member)[source]¶

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, a file-like object is returned. If member is a link, a file-like object is constructed from the link’s target. If member is none of the above, None is returned.

Note

The file-like object is read-only. It provides the methods read(), readline(), readlines(), seek(), tell(), and close(), and also supports iteration over its lines.

TarFile.add(name, arcname=None, recursive=True, exclude=None, filter=None)[source]¶

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. If 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). If filter is specified it must 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 2.6: Added the exclude parameter.

Changed in version 2.7: Added the filter parameter.

Deprecated since version 2.7: The exclude parameter is deprecated, please use the filter parameter instead. For maximum portability, filter should be used as a keyword argument rather than as a positional argument so that code won’t be affected when exclude is ultimately removed.

TarFile.addfile(tarinfo, fileobj=None)[source]¶

Add the TarInfo object tarinfo to the archive. If fileobj is given, tarinfo.size bytes are read from it and added to the archive. You can create TarInfo objects directly, or by using gettarinfo().

Note

On Windows platforms, fileobj should always be opened with mode 'rb' to avoid irritation about the file size.

TarFile.gettarinfo(name=None, arcname=None, fileobj=None)[source]¶

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. 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.

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.

TarFile.close()[source]¶

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

TarFile.posix¶

Setting this to True is equivalent to setting the format attribute to USTAR_FORMAT, False is equivalent to GNU_FORMAT.

Changed in version 2.4: posix defaults to False.

Deprecated since version 2.6: Use the format attribute instead.

TarFile.pax_headers¶

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

New in version 2.6.

5.2. 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="")[source]¶

Create a TarInfo object.

TarInfo.frombuf(buf)[source]¶

Create and return a TarInfo object from string buffer buf.

New in version 2.6: Raises HeaderError if the buffer is invalid..

TarInfo.fromtarfile(tarfile)[source]¶

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

New in version 2.6.

TarInfo.tobuf(format=DEFAULT_FORMAT, encoding=ENCODING, errors='strict')[source]¶

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

Changed in version 2.6: The arguments were added.

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¶

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.

New in version 2.6.

A TarInfo object also provides some convenient query methods:

TarInfo.isfile()[source]¶

Return True if the Tarinfo object is a regular file.

TarInfo.isreg()[source]¶

Same as isfile().

TarInfo.isdir()[source]¶

Return True if it is a directory.

TarInfo.issym()[source]¶

Return True if it is a symbolic link.

TarInfo.islnk()[source]¶

Return True if it is a hard link.

TarInfo.ischr()[source]¶

Return True if it is a character device.

TarInfo.isblk()[source]¶

Return True if it is a block device.

TarInfo.isfifo()[source]¶

Return True if it is a FIFO.

TarInfo.isdev()[source]¶

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

5.3. 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 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",
    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()

5.4. 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 gigabytes. 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 gigabytes 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.

5.5. 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 (that all other formats are merely variants of) 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. Names (i.e. filenames, linknames, user/group names) containing these characters 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 names using the universal character encoding UTF-8. When a pax archive is read, these UTF-8 names are converted to the encoding of the local file system.

The details of unicode conversion are controlled by the encoding and errors keyword arguments of the TarFile class.

The default value for encoding is the local character encoding. It is deduced from sys.getfilesystemencoding() and sys.getdefaultencoding(). In read mode, encoding is used exclusively to convert unicode names from a pax archive to strings in the local character encoding. In write mode, the use of encoding depends on the chosen archive format. In case of PAX_FORMAT, input names that contain non-ASCII characters need to be decoded before being stored as UTF-8 strings. The other formats do not make use of encoding unless unicode objects are used as input names. These are converted to 8-bit character strings before they are added to the archive.

The errors argument defines how characters are treated that cannot be converted to or from encoding. Possible values are listed in section Codec Base Classes. In read mode, there is an additional scheme 'utf-8' which means that bad characters are replaced by their UTF-8 representation. This is the default scheme. In write mode the default value for errors is 'strict' to ensure that name information is not altered unnoticed.