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Gzip
gzip is a file format and a software application for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (from which the "g" of gzip is derived). Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993.
As the file format can be decompressed via a streaming algorithm, it is commonly used in stream-based technology such as Web protocols, data interchange and ETL (in standard pipes).
A gzip file (described in the table below) contains a 10-byte header, optional extra header fields, a DEFLATE-compressed payload and an 8-byte trailer.
gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding. DEFLATE was intended as a replacement for LZW and other patent-encumbered data compression algorithms which, at the time, limited the usability of the compress utility and other popular archivers.
Although multiple streams may be concatenated (gzipped files are simply decompressed concatenated as if they were originally one file), normally only a single file is compressed. Compressed archives are typically created by assembling collections of files into a single tar archive (also called tarball), and then compressing that archive with gzip. The final compressed file usually has the extension .tar.gz or .tgz.
gzip is not to be confused with the ZIP archive format, which also uses DEFLATE. The ZIP format can hold collections of files without an external archiver, but is less compact than compressed tarballs holding the same data, because it compresses files individually and cannot take advantage of redundancy between files (solid compression).
The gzip file format is also not to be confused with that of the compress utility, based on LZW, with extension .Z; however, the gunzip utility is able to decompress .Z files.
All multi-byte values are encoded in little-endian.
Various implementations of the program have been written. The most commonly known is the GNU Project's implementation using Lempel-Ziv coding (LZ77). OpenBSD's version of gzip is actually the compress program, to which support for the gzip format was added in OpenBSD 3.4. The "g" in this specific version stands for gratis. FreeBSD, DragonFly BSD and NetBSD use a BSD-licensed implementation instead of the GNU version; it is actually a command-line interface for zlib intended to be compatible with the GNU implementations' options. These implementations originally come from NetBSD, and support decompression of bzip2 and the Unix pack format.
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Gzip
gzip is a file format and a software application for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (from which the "g" of gzip is derived). Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993.
As the file format can be decompressed via a streaming algorithm, it is commonly used in stream-based technology such as Web protocols, data interchange and ETL (in standard pipes).
A gzip file (described in the table below) contains a 10-byte header, optional extra header fields, a DEFLATE-compressed payload and an 8-byte trailer.
gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding. DEFLATE was intended as a replacement for LZW and other patent-encumbered data compression algorithms which, at the time, limited the usability of the compress utility and other popular archivers.
Although multiple streams may be concatenated (gzipped files are simply decompressed concatenated as if they were originally one file), normally only a single file is compressed. Compressed archives are typically created by assembling collections of files into a single tar archive (also called tarball), and then compressing that archive with gzip. The final compressed file usually has the extension .tar.gz or .tgz.
gzip is not to be confused with the ZIP archive format, which also uses DEFLATE. The ZIP format can hold collections of files without an external archiver, but is less compact than compressed tarballs holding the same data, because it compresses files individually and cannot take advantage of redundancy between files (solid compression).
The gzip file format is also not to be confused with that of the compress utility, based on LZW, with extension .Z; however, the gunzip utility is able to decompress .Z files.
All multi-byte values are encoded in little-endian.
Various implementations of the program have been written. The most commonly known is the GNU Project's implementation using Lempel-Ziv coding (LZ77). OpenBSD's version of gzip is actually the compress program, to which support for the gzip format was added in OpenBSD 3.4. The "g" in this specific version stands for gratis. FreeBSD, DragonFly BSD and NetBSD use a BSD-licensed implementation instead of the GNU version; it is actually a command-line interface for zlib intended to be compatible with the GNU implementations' options. These implementations originally come from NetBSD, and support decompression of bzip2 and the Unix pack format.
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