pack (compression)

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Filename extension .z
Type of format data compression

Pack is a (now deprecated) Unix shell compression program based on Huffman coding.[1]

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 will be uncompressed to the standard output.

Although obsolete, support for pack'd files exists in modern compression tools such as gzip and 7-zip.

Description of program[edit]

Files compressed by pack are typically given the extension ".z" (not to be confused with the ".Z" of 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.


Command-line parameters to unpack are specified like this:

unpack switches files

Some of the switches that can modify the output are

  • -f: force. Normally if a file cannot be compressed, it isn't.
  • -o {filename}: output file. Specifies a different output file so that compressed output is written to different file, rather than replacing the original file with the '.z' compressed version.

See also[edit]


  1. ^ "Compress and uncompress of files in UNIX", Superuser, retrieved 14 January 2013

External links[edit]

  • pack(1) - Manual page for the pack command.