The tarfile module makes it possible to read and write tar archives, including those using gzip or bz2 compression. (.zip files can be read and written using the zipfile module.)
Some facts and figures:
mode has to be a string of the form 'filemode[:compression]', it defaults to 'r'. Here is a full list of mode combinations:
|'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.|
|'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.|
Note that 'a:gz' or 'a:bz2' 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 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). 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 to be accessed randomly, see Examples. The currently possible modes:
|'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.|
|'w|'||Open an uncompressed stream for writing.|
|'w|gz'||Open an gzip compressed stream for writing.|
|'w|bz2'||Open an bzip2 compressed stream for writing.|
The tarfile module defines the following exceptions:
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.
The following variables are available on module level:
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.
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.
fileobj is not closed, when TarFile is closed.
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 or IOError 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.
If a member occurs more than once in the archive, its last occurrence is assumed to be the most up-to-date version.
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.
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 "..".
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.
See the warning for extractall().
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.
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.
On Windows platforms, fileobj should always be opened with mode 'rb' to avoid irritation about the file size.
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.
Create and return a TarInfo object from string buffer buf.
Raises HeaderError if the buffer is invalid..
A TarInfo object has the following public data attributes:
A TarInfo object also provides some convenient query methods:
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) == ".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()
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()
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 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 Codec Base Classes. In read mode the default scheme is 'replace'. This avoids unexpected UnicodeError exceptions and guarantees that an archive can always be read. In write mode the default value for errors is 'strict'. This ensures that name information is not altered unnoticed.
In case of writing PAX_FORMAT archives, encoding is ignored because non-ASCII metadata is stored using UTF-8.