# Pack (software)

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Pack Filename extension .z Type of format data compression

**Pack** is a legacy [Unix shell](/source/Unix_shell) [compression program](/source/Compression_program) based on [Huffman coding](/source/Huffman_coding).[1][2]

The **unpack** utility will restore files to their original state after they have been compressed using the *pack* utility. If no files are specified, the [standard input](/source/Standard_input) will be uncompressed to the standard output.

Although obsolete, support for packed files exists in modern compression tools such as [gzip](/source/Gzip)[3] and [7-zip](/source/7-zip).

## Description of program

Files compressed by *pack* are typically given the [extension](/source/Filename_extension) ".z" (not to be confused with the ".Z" of [compress](/source/Compress)). Files can be returned to their original state using *unpack*. In addition, there may also be a *pcat* command which reads in a compressed file and sends its output to [stdout](/source/Stdout).

## See also

- [Data compression](/source/Data_compression)

- [Image compression](/source/Image_compression)

- [List of Unix commands](/source/List_of_Unix_commands)

## References

1. **[^](#cite_ref-1)** [pack(1)](http://man.cat-v.org/unix_8th/1/pack) – [Version 8 Unix](/source/Version_8_Unix) Programmer's [Manual](/source/Man_page)

1. **[^](#cite_ref-2)** [pack(1)](https://docs.oracle.com/cd/E88353_01/html/E37839/pack-1.html) – [Solaris 11.4](/source/Solaris_(operating_system)) User Commands Reference [Manual](/source/Man_page)

1. **[^](#cite_ref-3)** Holen, Vidar. ["An ode to pack: gzip's forgotten decompressor"](https://www.vidarholen.net/contents/blog/?p=691). *Vidar’s Blog: GNU, Linux and technology in general*. Retrieved 16 November 2018.

## External links

- [pack(1)](https://pubs.opengroup.org/onlinepubs/007908799/xcu/pack.html) in The Single UNIX Specification, Version 2, 1997, opengroup.org

- [C.4 Utilities](https://pubs.opengroup.org/onlinepubs/009695399/xrat/xcu_chap04.html) in The Open Group Base Specifications Issue 6, opengroup.org – indicates pack as excluded

- [pack(1)](http://man.cat-v.org/unix_8th/1/pack) – [Version 8 Unix](/source/Version_8_Unix) Programmer's [Manual](/source/Man_page)

- [pack(1)](https://docs.oracle.com/cd/E88353_01/html/E37839/pack-1.html) – [Solaris 11.4](/source/Solaris_(operating_system)) User Commands Reference [Manual](/source/Man_page)

- [Pack command Manual](https://archive.org/stream/UNIXManRel5/301-925_I1#page/n282/mode/1up)

v t e Data compression software Archivers with compression (comparison) Free and open-source 7-Zip Ark Expander File Roller FreeArc Info-ZIP KGB Archiver PAQ pax PeaZip XAD (decompression only) Xarchiver Zipeg ZPAQ Freeware Filzip LHA StuffIt Expander (decompression only) The Unarchiver (decompression only) TUGZip ZipGenius Commercial ARC ALZip Archive Utility ARJ BetterZip MacBinary PKZIP/SecureZIP PowerArchiver StuffIt WinAce WinRAR WinZip Non-archiving compressors Generic bzip2 compress gzip lzip lzop pack rzip Snappy XZ Utils zstd For code UPX Audio compression (comparison) Lossy AAC Fraunhofer FDK AAC Nero AAC Codec FAAC Helix DNA Producer MP3 l3enc LAME TooLAME libavcodec libcelt libopus libspeex Musepack libvorbis Windows Media Encoder Lossless ALAC FLAC libavcodec Monkey's Audio mp4als OptimFROG Shorten WavPack Video compression (comparison) Lossy MPEG-4 ASP 3ivx DivX Nero Digital FFmpeg HDX4 Xvid H.264 CoreAVC Blu-code DivX FFmpeg Nero Digital OpenH264 QuickTime x264 HEVC DivX x265 Others CineForm Cinepak Daala DNxHD Helix DNA Producer Indeo libavcodec Schrödinger (Dirac) SBC Sorenson VP7 libtheora libvpx Windows Media Encoder Lossless FFV1 Huffyuv Lagarith MSU Lossless YULS See also: compression methods and compression formats

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