Ausam/doc/man/man1/pack.1

.th PACK I 12/12/75
.sh NAME
pack  \*-  compress files
.sh SYNOPSIS
.bd pack
[-] [\fB-s\fR] filename ...
.sh DESCRIPTION
Packs the specified files.  Each input file, f, is replaced by
a packed file, f.z, with the same mode as that of f.  Packed files
can be restored to their original form using unpack(I) or pcat(I).
.s3
.it Pack
uses Huffman (minimum redundancy) codes on a byte by byte
basis.  If the `-' flag argument is used, the number of times each
byte is used, its relative frequency, and the code for the byte
is printed on the standard output.
.s3
The amount of compression obtained depends on the size of the
input file, and the character distribution.  Since a decoding
tree forms the first part of the '.z' files, it is not worthwhile
to pack files smaller than three blocks, unless the character
distribution is very skewed, such as in printer plots or pictures.
If no disk blocks are saved by packing, the original file will be
left unchanged.
.s3
Typically, text files are reduced to 60-75% of their original size;
Load modules, which use a larger character set and have a more
uniform distribution of characters, show little compression, the
packed versions being about 90% of the original size.
.s3
If the
.it -s
flag is used, the modified time of the
.it .z
files will be set to that of the original files. This is
useful when pack is used to recover disk space so as not to
interfere with incremental dumps.
.sh RESTRICTIONS
The last segment of the filename must contain fewer than thirteen
characters to allow space for the appended '.z' extension.
Directories cannot (and should not) be compressed.
.sh FILES
.it .z
Files created
.br
Input files unlinked (unless protected)
.sh "SEE ALSO"
UNPACK(I), PCAT(I), SMDATE(II)
.sh AUTHOR
Steve Zucker