Бірнеше файлды біріктіретін tar архиві туралы

Computer file format that can combine multiple files into a single file called "tarball"

In computing, tar is a computer software utility for collecting many files into one archive file, often referred to as a tarball, for distribution or backup purposes. The name is derived from "tape archive", as it was originally developed to write data to sequential I/O devices with no file system of their own, such as devices that use magnetic tape. The archive data sets created by tar contain various file system parameters, such as name, timestamps, ownership, file access permissions, and directory organization. POSIX abandoned tar in favor of pax, yet tar sees continued widespread use.

The command line utility was first introduced in the Version 7 Unix in January 1979, replacing the tp program (which in turn replaced "tap"). The file structure to store this information was standardized in POSIX.1 1988 and later POSIX.1 2001, and became a format supported by most modern file archiving systems. The tar command was abandoned in POSIX.1 2001 in favor of pax command, which was to support ustar file format; the tar command was indicated for withdrawal in favor of pax command at least since 1994. Today, Unix like operating systems usually include tools to support tar files, as well as utilities commonly used to compress them, such as xz, gzip, and bzip2. The command has also been ported to the IBM i operating system. BSD tar has been included in Microsoft Windows since Windows 10 April 2018 Update, and there are otherwise multiple third party tools available to read and write these formats on Windows.

Many historic tape drives read and write variable length data blocks, leaving significant wasted space on the tape between blocks (for the tape to physically start and stop moving). Some tape drives (and raw disks) support only fixed length data blocks. Also, when writing to any medium such as a file system or network, it takes less time to write one large block than many small blocks. Therefore, the tar command writes data in records of many 512 B blocks. The user can specify a blocking factor, which is the number of blocks per record. The default is 20, producing 10 KiB records.

There are multiple tar file formats, including historical and current ones. Two tar formats are codified in POSIX: ustar and pax. Not codified but still in current use is the GNU tar format. A tar archive consists of a series of file objects, hence the popular term tarball, referencing how a tarball collects objects of all kinds that stick to its surface. Each file object includes any file data, and is preceded by a 512 byte header record. The file data is written unaltered except that its length is rounded up to a multiple of 512 bytes. The original tar implementation did not care about the contents of the padding bytes, and left the buffer data unaltered, but most modern tar implementations fill the extra space with zeros. The end of an archive is marked by at least two consecutive zero filled records. (The origin of tar's record size appears to be the 512 byte disk sectors used in the Version 7 Unix file system.) The final block of an archive is padded out to full length with zeros.

The tar format continues to be used extensively for open source software distribution. *NIX distributions use it in various source and binary package distribution mechanisms, with most software source code made available in compressed tar archives.

The original tar format was created in the early days of Unix, and despite current widespread use, many of its design features are considered dated. Many older tar implementations do not record nor restore extended attributes (xattrs) or access control lists (ACLs). In 2001, Star introduced support for ACLs and extended attributes, through its own tags for POSIX.1 2001 pax. bsdtar uses the star extensions to support ACLs. More recent versions of GNU tar support Linux extended attributes, reimplementing star extensions. A number of extensions are reviewed in the filetype manual for BSD tar, tar(5). If a user has only a very old tar available, which does not feature those security measures, these problems can be mitigated by first examining a tar file using the command tar tf archive. tar, which lists the contents and allows to exclude problematic files afterwards. These commands do not extract any files, but display the names of all files in the archive. If any are problematic, the user can create a new empty directory and extract the archive into it—or avoid the tar file entirely. Most graphical tools can display the contents of the archive before extracting them. Vim can open tar archives and display their contents. GNU Emacs is also able to open a tar archive and display its contents in a dired buffer.

The tar format was designed without a centralized index or table of content for files and their properties for streaming to tape backup devices. The archive must be read sequentially to list or extract files. For large tar archives, this causes a performance penalty, making tar archives unsuitable for situations that often require random access to individual files. With a well formed tar file stored on a seekable (i. e. allows efficient random reads) medium, the program can still relatively quickly (in linear time relative to file count) look for a file by skipping file reads according to the "size" field in the file headers. This is the basis for option in GNU tar. When a tar file is compressed whole, the compression format, being usually non seekable, prevents this optimization from being done. A number of "indexed" compressors, which are aware of the tar format, can restore this feature for compressed files. To maintain seekability, tar files must be also concatenated properly, by removing the trailing zero block at the end of each file.

Another issue with tar format is that it allows several (possibly different) files in archive to have identical paths and filenames. When extracting such archive, usually the latter version of a file overwrites the former. This can create a non explicit (unobvious) tarbomb, which technically does not contain files with absolute paths or referring parent directories, but still causes overwriting files outside current directory (for example, archive may contain two files with the same path and filename, first of which is a symlink to some location outside current directory, and second of which is a regular file; then extracting such archive on some tar implementations may cause writing to the location pointed to by the symlink).

tar archive files usually have the file suffix tar (e. g. somefile. tar). A tar archive file contains uncompressed byte streams of the files which it contains. To achieve archive compression, a variety of compression programs are available, such as gzip, bzip2, xz, lzip, lzma, zstd, or compress, which compress the entire tar archive. Typically, the compressed form of the archive receives a filename by appending the format specific compressor suffix to the archive file name. For example, a tar archive archive. tar, is named archive. tar. gz, when it is compressed by gzip. Popular tar programs like the BSD and GNU versions of tar support the command line options Z (compress), z (gzip), and j (bzip2) to compress or decompress the archive file upon creation or unpacking. Relatively recent additions include lzma (LZMA), lzop (lzop), xz or J (xz), lzip (lzip), and zstd. The decompression of these formats is handled automatically if supported filename extensions are used, and compression is handled automatically using the same filename extensions if the option auto compress (short form a) is passed to an applicable version of GNU tar. Unrecognized formats are to be manually compressed or decompressed by piping. MS DOS's 8.3 filename limitations resulted in additional conventions for naming compressed tar archives. However, this practice has declined with FAT now offering long filenames. + File suffix equivalentsCompressor Long Shortbzip2 tar. bz2 tb2, tbz, tbz2, tz2gzip tar. gz taz, tgzlzip tar. lz lzma tar. lzma tlzlzop tar. lzo xz tar. xz txzcompress tar. Z tZ, taZzstd tar. zst tzst