 Technical Briefs
ROHAN help Files
gzip, gunzip, zcat
gzip uses the Lempel-Ziv algorithm used in zip and PKZIP.
The amount of compression obtained depends on the size of the input and the
distribution of common substrings. Typically, text such as source code or
English is reduced by 60-70%. Compression is generally much better than
that achieved by LZW (as used in compress), Huffman coding (as used in pack),
or adaptive Huffman coding (compact). Each file is replaced by one with the
extension .z If no files are specified, the standard input is compressed
to the standard output.
Compression is always performed, even if the compressed file is slightly
larger than the original. The worst case expansion is a few bytes for the
gzip file header, plus 5 bytes every 32K block, or an expansion ratio
of 0.015% for large files.
Compressed files can be restored to their original form, Syntax is:
rohan% gzip -d filename
where filename is the name of the compressed file. gunzip and zcat
can replace gzip.
Note: the GNU compression programs (gzip, gunzip, zcat) give better
compression rations and will uncompress files created by compress.
|
|
ROHAN Help Index