Tar (computing)

In computing, tar is a computer software utility for collecting many files into one , 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. The archive data sets created by tar contain various 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 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.