FREEZE(1) UNIX System V (local) FREEZE(1)
NAME
freeze, melt, fcat - compress and uncompress files
SYNOPSIS
freeze [ -cdfvVg ] [ filename | +type ... ]
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 (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 40% faster heuristic is
used. The more times this flag is present, the faster
program works and the less compression rate is. This flag is
quite useful 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 '+', which defines the type of
following files in the command string. An explicite
definition of the file's type can give up to 2% of
additional compression. The list of types is stored in file
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FREEZE(1) UNIX System V (local) FREEZE(1)
/etc/default/freeze. 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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FREEZE(1) UNIX System V (local) FREEZE(1)
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
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FREEZE(1) UNIX System V (local) FREEZE(1)
header of frozen file.
BUGS
Found bugs descriptions, incompatibilities, etc. please
send to leo@s514.ipmce.su.
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