FREEZE(1) FREEZE(1)
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NAME
freeze, unfreeze, melt, fcat - compress and uncompress files
SYNOPSIS
freeze [ -cdfvVgx ] [ filename | type ... ]
unfreeze [ -cfvV ] [ filename ... ]
melt [ -cfvV ] [ filename ... ]
fcat [ filename ... ]
DESCRIPTION
Compresses the specified files or standard input. Each file is
replaced by a file with the extension .F, but only if the file got
smaller. If no files are specified, the compression is applied to the
standard input and is written to standard output regardless of the
results. Compressed files can be restored to their original form by
specifying the -d option, or by running melt or unfreeze (both linked
to freeze), on the .F files or the standard input.
If the output file exists, it will not be overwritten unless the -f
flag is given. If -f is not specified and freeze is run in the
foreground, the user is prompted as to whether the file should be
overwritten.
If the -g flag is given, a slightly less powerful (compression rate is
1.5% less), but somewhat faster heuristic is used. This flag can be
used more than once (this mode is quite useful when freezing bitmaps)
for additional speedup.
If you want to improve compression rate at the cost of speed, use -x
flag. It means "maximum compression" (the speed may degrade
substantially when freezing bitmaps).
If the -f flag is given, all files specified are replaced with .F
files - even if the file didn't get smaller.
When file names are given, the ownership (if run by root), modes,
accessed and modified times are maintained between the file and its .F
version. In this respect, freeze can be used for archival purposes,
yet can still be used with make(1) after melting.
The -c option causes the results of the freeze/melt operation to be
written to stdout; no files are changed. The fcat program is the same
as specifying -c to melt (all files are unpacked and written to
stdout).
The -v (verbose) option causes the diagnostics (at the end of each
file processing) to be printed to stderr, and the -vv option causes
the progress indicator to be drawn to the same place.
Type is a token preceded by a '+' or a '--', which defines the type of
following files in the command string. An explicite definition of the
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file's type can give up to 2% of additional compression. The list of
types is stored in file /usr/local/lib/freeze.cnf. Types may be
abbreviated while not ambigious. You can also determine values for the
static Huffman table by using a list of 8 numbers separated by commas
instead of type.
Freeze uses the Lempel-Ziv algorithm on the first pass and the dynamic
Huffman algorithm on the second one. The size of sliding window is 8K,
and the maximum length of matched string is 256. The positions on the
window are coded using a static Huffman table.
A two byte magic number is prepended to the file to ensure that
neither melting of random text nor refreezing of already frozen text
are attempted. In addition, the characteristics of the static Huffman
table being used during freeze is written to the file so that these
characteristics may be adapted to concrete conditions.
The amount of compression obtained depends on the size of the input
file and the distribution of character substrings and their
probabilities. Typically, text files, such as C programs, are reduced
by 60-75%, executable files are reduced by 50%. Compression is
generally much better than that achieved by LZW coding (as used in
compress), or Huffman coding (pack), though takes more time to
compute.
If the -V (version) flag is given, the program's version number and
compilation options are printed.
The exit status is normally 0; if the last file gets bigger after
freezing, the exit status is 2; if an error occurs, the exit status is
1.
SEE ALSO
compact(1), pack(1), compress(1)
DIAGNOSTICS
Unknown flag: 'x'; Usage: freeze [-cdfvVg] [file|+type ...]
Invalid options were specified on the command line.
file: not in frozen format
The specified file has not been frozen.
file: already has .F suffix -- no change
Cannot compress a file that has a ".F" suffix. mv(1) the file
to a different name and try again.
file: filename too long to tack on .F
The specified file cannot be compressed because its filename
is longer than 12 characters. mv(1) the file to a different
name and try again. This message does not occur on 4.XBSD
systems.
file already exists; do you wish to overwrite (y or n)?
Respond "y" if you want the output file to be replaced; "n" if
you want it to be left alone.
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file: xx%
or
xxxK
These message fragments are written during the processing of a
file, if -vv option was given in the command line (in
percents, if the length of file being processed is known; in
Kbytes otherwise).
Freezing: xx.xx% (y.yy bits)
This message fragment gives the percentage of the input file
that has been saved by freezing and the number of remaining
bits per byte of original file.
-- not a regular file: unchanged
This message fragment is written when the input file is not a
regular file. The input file is left unchanged.
-- has xx other links: unchanged
This message fragment is written when the input file has
links. The input file is left unchanged. See ln(1) for more
information.
-- file unchanged
This message fragment is written when no savings are achieved
by freezing. The input file is left unchanged.
-- replaced with file
This message fragment is written when a file has been
sucessfully frozen/melt.
Using " type " type
This message indicates a successful switching to position
table for mentioned file type.
" xxx " - no such file type
or
xxx - a list of 8 numbers expected
This message means the given file type does not exist or the
given string contains a comma, but is not a valid list of
values for static Huffman table.
melt: corrupt input
This message fragment is written when an error in header or
unexpected end of frozen file is detected. Partial (or empty,
is there was an error in the header) file is created.
already frozen -- file unchanged
This message fragment is written when an input file already
has Freeze's magic header.
Invalid position table
or
" type " - invalid entry
These messages appear only if Freeze has been made with
incorrect data for static Huffman table. It does never appear
when freeze is called from a public access directory.
Unknown header format
Unknown values of flag bits were discovered in the header of
frozen file.
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BUGS
Found bugs descriptions, incompatibilities, etc. please send to
leo@ipmce.su.
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