compact(1) General Commands Manual compact(1)Name
compact, uncompact, ccat - compress and uncompress files, and cat them
Syntax
compact [name...]
uncompact [name...]
ccat [file...]
Description
The command compresses the named files using an adaptive Huffman code. If no file names are given, the standard input is compacted to the
standard output. The command operates as an on-line algorithm. Each time a byte is read, it is encoded immediately according to the cur-
rent prefix code. This code is an optimal Huffman code for the set of frequencies seen so far. It is unnecessary to prepend a decoding
tree to the compressed file since the encoder and the decoder start in the same state and stay synchronized. Furthermore, and can operate
as filters. In particular,
... | compact | uncompact | ...
operates as a (very slow) no-op.
When an argument file is given, it is compacted and the resulting file is placed in file.C; file is unlinked. The first two bytes of the
compacted file code the fact that the file is compacted. This code is used to prohibit recompaction.
The amount of compression to be expected depends on the type of file being compressed. Typical values of compression are: Text (38%), Pas-
cal Source (43%), C Source (36%) and Binary (19%). These values are the percentages of file bytes reduced.
The command restores the original file from a file compressed by If no file names are given, the standard input is uncompacted to the stan-
dard output.
The command cats the original file from a file compressed by without uncompressing the file.
The command is present only for compatibility. In general, the command runs faster and gives better compression.
Restrictions
The last segment of the file name must contain fewer than thirteen characters to allow space for the appended '.C'.
Files
compacted file created by compact, removed by uncompact
See Alsocompress(1)compact(1)
Check Out this Related Man Page
compact(1) General Commands Manual compact(1)NAME
compact, uncompact, ccat - compact and uncompact files, and cat them
SYNOPSIS
[sfile] ...
[cfile] ...
[cfile] ...
DESCRIPTION
compresses the named files using an adaptive Huffman code. If no file names are given, standard input is compacted and sent to the stan-
dard output. operates as an on-line algorithm. Each time a byte is read, it is encoded immediately according to the current prefix code.
This code is an optimal Huffman code for the set of frequencies seen so far. It is unnecessary to attach a decoding tree in front of the
compressed file because the encoder and the decoder start in the same state and stay synchronized. Furthermore, and can operate as fil-
ters. In particular,
operates as a (very slow) no-op.
When an argument file is given, it is compacted, the resulting file is placed in and file is unlinked. The first two bytes of the com-
pacted file code the fact that the file is compacted. These bytes are used to prohibit recompaction.
The amount of compression to be expected depends on the type of file being compressed. Typical file size reduction (in percent) through
compression are: Text, 38%; Pascal Source, 43%; C Source, 36%; and Binary, 19%.
restores the original file from a file compressed by If no file names are specified, standard input is uncompacted and sent to the standard
output.
writes the specified c_file, compressed by to standard output, without uncompressing the file.
Operands
The commands recognize the following operands:
cfile Compacted file.
sfile Source file to compact or uncompact. If no file names are given, the commands use standard input and sent to the standard
output. places the compacted file in
Access Control Lists (ACLs)
On systems that implement access control lists, when a new file is created with the effective user and group ID of the caller, the original
file's ACL is copied to the new file after being altered to reflect any change in ownership (see acl(5) and aclv(5)). In JFS file systems,
files created by or do not inherit their parent directory's default ACL entries (if any), but instead retain their original ACLs. When a
file being compacted or uncompacted resides on a JFS file system, and the compacted or uncompacted file resides on an HFS file system (or
vice versa), as the result of or the use of or as a filter, optional ACL entries are lost.
WARNINGS
On short-file-name systems, the last segment of the file name must contain 12 or fewer characters to allow space for the appended
DEPENDENCIES
NFS
Access control list entries of networked files are summarized (as returned in by but not copied to the new file (see stat(2)).
AUTHOR
was developed by Colin L. Mc Master.
FILES
compacted file created by compact, removed by uncompact
SEE ALSO compress(1), pack(1), acl(5), aclv(5).
Gallager, Robert G., "Variations on a Theme of Huffman," vol. IT-24, no. 6, November 1978, pp. 668 - 674.
compact(1)