pack, pcat, unpack — Compress and Expand Files
/usr/bin/pack [-f][-] file... /usr/bin/pcat file... /usr/bin/unpack file...
The pack command stores the specified files in a compressed form. Wherever possible (and useful), each specified input file is replaced by a packed file named file .z with the same access modes, access and modified dates, and owner as those of file . When the pack is successful, the original file is removed.
The size of the input file and the character frequency distribution determine the amount of compression. Because a decoding tree forms the first part of each .z file, it is usually not worthwhile to pack files smaller than three blocks. You may find it worthwhile, however, to pack small ...