Thus if all the files in an archive are ASCII text files, and have ASCII names, then the archive is essentially an ASCII text file (containing many NUL characters). To ensure portability across different architectures with different byte orderings, the information in the header record is encoded in ASCII. The file header record contains metadata about a file. (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 end of an archive is marked by at least two consecutive zero-filled records. 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 file data is written unaltered except that its length is rounded up to a multiple of 512 bytes. Each file object includes any file data, and is preceded by a 512-byte header record. Not codified but still in current use is the GNU tar format.Ī 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. Two tar formats are codified in POSIX: ustar and pax. There are multiple tar file formats, including historical and current ones. The default is 20, producing 10 KiB records. The user can specify a blocking factor, which is the number of blocks per record. Therefore, the tar command writes data in records of many 512 B 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. Some tape drives (and raw disks) support only fixed-length data blocks. 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). īSD-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. The tar command has also been ported to the IBM i operating system. 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 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. 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 command-line utility was first introduced in the Version 7 Unix in January 1979, replacing the tp program (which in turn replaced "tap"). POSIX abandoned tar in favor of pax, yet tar sees continued widespread use. The archive data sets created by tar contain various file system parameters, such as name, timestamps, ownership, file-access permissions, and directory organization. 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. 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. Both XZ and TAR are more commonly used on Unix-style OS'es like FreeBSD and GNU/Linux.POSIX since POSIX.1, presently in the definition of pax tar archive ('tarball') is used to consolidate files and directories into a single file, whereupon that file is compressed with the XZ method (.tar.xz or. XZ supports single-file compression only, which is why it is often used in conjunction with TAR. On Microsoft Windows, several free and paid archive managers additionally support the XZ format and are capable of handling. XZ archives are natively handled by XZ Utils (formerly, LZMA Utils) which are the reference XZ implementation, available on a range of platforms and OS'es. XZ is closely related to the open-source 7-Zip archive manager and the LZMA SDK (public domain).Īn. Like LZMA, XZ is integer-based and allows to achieve very high compression ratios. XZ is the name of an open data compression algorithm, a derivative of the earlier LZMA format, that originated within The Tukaani Project (formerly a Slackware-based GNU/Linux distribution). xz filename extension belongs to the XZ Compressed Archive (.xz) file format and type.
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