tarformat

tarformat refers to the structure and organization of data within a tar archive file. Tar, which stands for Tape Archive, is a common file format used for bundling multiple files and their associated metadata into a single file. This bundling process is often referred to as "tarring." The tar format is primarily used on Unix-like operating systems for purposes such as backups, software distribution, and file transfer.

A tar archive is essentially a stream of data. Each file within the archive is preceded by a header block that contains information about the file, such as its name, size, permissions, owner, and modification time. Following the header block is the actual data content of the file. This structure is repeated for every file in the archive. Multiple header-data pairs are concatenated together to form the complete tar file.

The original tar format, often referred to as "ustar" (Unix Standard Tar), has a fixed header size and specific field layouts. This standardization ensures that tar archives can be read and extracted by different tar utilities across various systems. Over time, extensions and variations of the tar format have emerged to support larger file sizes, extended attributes, and compression. Common compression methods like gzip, bzip2, and xz are often applied to tar archives, resulting in files with extensions like .tar.gz, .tar.bz2, or .tar.xz, although these compressed files are technically not part of the tar format itself but rather an additional layer of compression applied to a tar archive.