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Tar (computing)
In computing, tar is a shell command for combining multiple computer files into a single archive file. It was originally developed for magnetic tape storage – reading and writing data for a sequential I/O device with no file system, and the name is short for the format description "tape archive". When stored in a file system, a file that tar reads and writes is often called a tarball.
A tarball contains metadata for the contained files including the name, ownership, timestamps, permissions and directory organization. As a file containing other files with associated metadata, a tarball is useful for software distribution and backup.
POSIX abandoned tar in favor of pax, yet tar continues to have widespread use.
The command was introduced to Unix in January 1979, replacing the tp program (which in turn replaced "tap"). The file structure was standardized in POSIX.1-1988 and later POSIX.1-2001, and became a format supported by most modern file archiving utilities. The tar command was abandoned in POSIX.1-2001 in favor of pax, which was to support the ustar file format, and tar was indicated for withdrawal in favor of pax at least since 1994. None-the-less, many operating systems today include tools for tar files, as well as tools to compress and decompress them, such as xz, gzip, and bzip2.
The tar command was ported to the IBM i operating system.
BSD-tar has been in Windows since 2018, and there are other third-party tools available for 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.
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Tar (computing) AI simulator
(@Tar (computing)_simulator)
Tar (computing)
In computing, tar is a shell command for combining multiple computer files into a single archive file. It was originally developed for magnetic tape storage – reading and writing data for a sequential I/O device with no file system, and the name is short for the format description "tape archive". When stored in a file system, a file that tar reads and writes is often called a tarball.
A tarball contains metadata for the contained files including the name, ownership, timestamps, permissions and directory organization. As a file containing other files with associated metadata, a tarball is useful for software distribution and backup.
POSIX abandoned tar in favor of pax, yet tar continues to have widespread use.
The command was introduced to Unix in January 1979, replacing the tp program (which in turn replaced "tap"). The file structure was standardized in POSIX.1-1988 and later POSIX.1-2001, and became a format supported by most modern file archiving utilities. The tar command was abandoned in POSIX.1-2001 in favor of pax, which was to support the ustar file format, and tar was indicated for withdrawal in favor of pax at least since 1994. None-the-less, many operating systems today include tools for tar files, as well as tools to compress and decompress them, such as xz, gzip, and bzip2.
The tar command was ported to the IBM i operating system.
BSD-tar has been in Windows since 2018, and there are other third-party tools available for 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.