TAR Archive Format
Docker layers, npm pack, Linux package sources, and backup workflows use tar. ustar and PAX extensions define long filenames and metadata.
What It Defines
Tape archive format: sequence of 512-byte header blocks (filename, mode, owner, size, type flag) followed by file content padded to 512-byte boundaries. Often combined with gzip (`.tar.gz` / `.tgz`). MIME type: `application/x-tar`.
Canonical (Normative)
Convenient (Practical)
Global consortium that maintains the Single UNIX Specification (SUS) and co-publishes POSIX (IEEE Std 1003.1) with the Austin Group (joint IEEE/The Open Group committee). POSIX defines the portable API for Unix-compatible systems: process model, file I/O, signals, sockets, and threads. The Open Group also certifies UNIX conformance for commercial operating systems.
Related Specs
`.gz` files, HTTP Content-Encoding: gzip, and tarball distribution (`.tar.gz`) all depend on this format. Know header vs raw DEFLATE stream.
ZIP is everywhere — downloads, backups, Java JARs, Office Open XML. Central-directory-at-end structure, path traversal (`../../`), and zip bombs are critical security concerns.