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1989-03-29
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COMPRESS COMPRESS
NAME
compress, uncompress, zcat--file compression utility
SYNOPSIS
compress [-dhHfvcV] [-b maxbits] [file ...]
DESCRIPTION
Compress is a file compression utility like (and completely compatible
with) the UNIX compress(1) program. It can be used to compress files by
name, or from standard input to standard output. As UNIX-style pipes are
not available on the Amiga, the latter capability is of dubious value, but
is included for the sake of completeness. Compress is able to function
with any output code maximum size from 12 bits to 16 bits. The higher the
maximum code size, the more efficient the compression, and the smaller the
resultant file, but higher sizes require more memory (e. g.: 16 bits
uses approximately 450K of RAM, most of which must be contiguous). For
systems with 1 Meg or less, 13 bits is the most useful for common use.
For systems with 1.5 Meg to 2.5 Meg, 15 bits is practical. The bitsize
can be selected in several ways: the -b command line option (more on this
below), a Manx-style environment variable, or the compiled-in default of
13 bits.
The environment variable, named COMPBITS, must have a value between 12 and
16, inclusive. It can be created using the "set" command supplied with
the Manx Aztec C compiler (for those who have it) or a variety of public-
domain commands that do the same thing.
Compress will take its input list of file names and, after compression,
deposit the compressed date in a file of the same name with a ".Z" appended
to the end of the file name. Thus, input file names are limited to 28
characters (to leave room for the terminating ".Z") due to the AmigaDOS
file name length limit.
Compress is a completely self-contained program, in that it can uncompress
any file it compressed. Decompression can be done by either using the -d
command line option or by naming the binary "uncompress" (the program
checks the value of argv[0]). Files can be catenated to standard output
by the use of the -c option or by naming the binary "zcat" (this property
is most useful when file links are available).
Compress will accept the following command line options:
-d: toggle decompression (uncompress) mode,
-h: usage diagnostic,
-H: more detailed help,
-f: force output to file regardless of conditions,
-v: toggle verbose mode on,
-c: toggle catenation (zcat) mode,
-V: print version,
-b: select maximum bit size.
SEE ALSO
arc, zoo.
DIAGNOSTICS
Prints help information with -h or -H options, prints message if one of
its calls to malloc() fails, prints a message if asked to uncompress a
file compressed with a higher bit size than it is currently using, and
prints messages concerning any problems with file names (file names are
limited to 28 characters, to leave room for the terminating ".Z"). Error
messages are generally unambiguous and informative, though the message
returned when one of the calls to malloc() fails are somewhat whimsical.
BUGS
None known. Please direct any questions, comments, or bug reports to:
Brent Woods
320 Brown St., #406
West Lafayette, IN 47906
Phone: (317) 743-8421