gzipDateiformat

gzipDateiformat, commonly referred to as the gzip file format, is a widely used method for compressing single files or streaming data using the DEFLATE compression algorithm. It was created by Jean-loup Gailly and Mark Adler and specified in RFC 1952 in 1996. The typical filename extension is .gz, and gzip is often used in conjunction with tar to form archives with a .tar.gz or .tgz extension.

A gzip file consists of a fixed-size header, a sequence of compressed data blocks, and a trailer. The header begins with a two-byte magic number 0x1F and 0x8B, followed by a compression method byte (0x08 for deflate) and a flag byte. The header may include the modification time, extra flags, operating system, and optional extra fields such as a filename or comment. The compressed data use the DEFLATE algorithm, which merges the LZ77 and Huffman coding steps. The trailer contains a CRC-32 checksum of the uncompressed data and the input size modulo 2^32.

Usage and limitations: The format is designed for single-file compression or streaming; it does not provide a built-in archive of multiple files, though tar can be used to create multi-file archives that are subsequently compressed. gzip streams can be concatenated; decompression yields the combined uncompressed data. In practice, gzip is ubiquitous on Unix-like systems and is supported by many libraries and command-line tools, such as gzip, gunzip, and zcat. For multi-file collections, the common approach is tar.gz.

Notes: Gzip is not a container; it is a compression wrapper around data compressed with DEFLATE. It is distinct from the ZIP format and from zlib's raw DEFLATE stream. The standard reference remains RFC 1952, and many implementations remain compatible with it.