svcadm(1M) 을 검색하려면 섹션에서 1M 을 선택하고, 맨페이지명에 svcadm을 입력하고 검색을 누른다.
compress
Name
compress, uncompress, zcat - compress, uncompress files or
display expanded files
Synopsis
compress [-fv/] [-b bits] [file]...
compress -c [-fv] [-b bits] [file]
uncompress [-fv] [-c | -/] [file]...
zcat [file]...
Description
compress
The compress utility attempts to reduce the size of the
named files by using adaptive Lempel-Ziv coding. Except when
the output is to the standard output, each file is replaced
by one with the extension .Z, while keeping the same owner-
ship modes, change times and modification times, ACLs, and
extended attributes. The compress utility also attempt to
set the owner and group of file.z to the owner and group of
file, but does not fail if this cannot be done. If appending
the .Z to the file pathname would make the pathname exceed
1023 bytes, the command fails. If no files are specified,
the standard input is compressed to the standard output.
The amount of compression obtained depends on the size of
the input, the number of bits per code, and the distribution
of common substrings. Typically, text such as source code or
English is reduced by 50-60%. Compression is generally much
better than that achieved by Huffman coding (as used in
pack(1)) and it takes less time to compute. The bits parame-
ter specified during compression is encoded within the
compressed file, along with a magic number to ensure that
neither decompression of random data nor recompression of
compressed data is subsequently allowed.
uncompress
The uncompress utility restores files to their original
state after they have been compressed using the compress
utility. If no files are specified, the standard input is
uncompressed to the standard output.
This utility supports the uncompressing of any files pro-
duced by compress. For files produced by compress on other
systems, uncompress supports 9- to 16-bit compression (see
-b).
zcat
The zcat utility writes to standard output the uncompressed
form of files that have been compressed using compress. It
is the equivalent of uncompress-c. Input files are not
affected.
Options
The following options are supported:
-b bits
Sets the upper limit (in bits) for common sub-
string codes. bits must be between 9 and 16 (16
is the default). Lowering the number of bits
result in larger, less compressed files.
-c
Writes to the standard output; no files are
changed and no .Z files are created. The behavior
of zcat is identical to that of `uncompress -c'.
-f
When compressing, forces compression of file,
even if it does not actually reduce the size of
the file, or if the corresponding file.Z file
already exists.
If the -f option is not specified, and the pro-
cess is not running in the background, prompts to
verify whether an existing file should be
overwritten. If the response is affirmative, the
existing file is overwritten. When uncompressing,
does not prompt for overwriting files. If the -f
option is not specified, and the process is not
running in the background, prompts to verify
whether an existing file should be overwritten.
If the standard input is not a terminal and -f is
not specified, writes a diagnostic message to
standard error and exits with a status greater
than 0.
-v
Verbose. Writes to standard error messages con-
cerning the percentage reduction or expansion of
each file.
-/
When compressing or decompressing, copies any
extended system attributes associated with the
source file to the target file and copies any
extended system attributes associated with
extended attributes of the source file to the
corresponding extended attributes associated with
the target file. If any extended system attri-
butes cannot be copied, the original file is
retained, a diagnostic is written to stderr, and
the final exit status is non-zero.
Operands
The following operand is supported:
file
A path name of a file to be compressed by compress,
uncompressed by uncompress, or whose uncompressed
form is written to standard out by zcat. If file is
-, or if no file is specified, the standard input is
used.
Usage
See largefile(5) for the description of the behavior of
compress, uncompress, and zcat when encountering files
greater than or equal to 2 Gbyte ( 2^31 bytes).
Environment Variables
See environ(5) for descriptions of the following environment
variables that affect the execution of compress, uncompress,
and zcat: LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES,
and NLSPATH.
Affirmative responses are processed using the extended regu-
lar expression defined for the yesexpr keyword in the
LC_MESSAGES category of the user's locale. The locale speci-
fied in the LC_COLLATE category defines the behavior of
ranges, equivalence classes, and multi-character collating
elements used in the expression defined for yesexpr. The
locale specified in LC_CTYPE determines the locale for
interpretation of sequences of bytes of text data a charac-
ters, the behavior of character classes used in the expres-
sion defined for the yesexpr. See locale(5).
Exit Status
The following error values are returned:
0
Successful completion.
1
An error occurred.
2
One or more files were not compressed because they
would have increased in size (and the -f option was
not specified).
>2
An error occurred.
Attributes
See attributes(5) for descriptions of the following attri-
butes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRI-
BUTE TYPEATTRIBUTE VALUE _ Availabilitysystem/core-os _
CSIEnabled _ Interface StabilityCommitted _ StandardSee
standards(5).
See Also
ln(1), pack(1), fgetattr(3C), fsetattr(3C), attributes(5),
environ(5), largefile(5), locale(5), standards(5)
Diagnostics
Usage: compress [-fv/] [-b bits] [file... ]
compress c [-fv] [-b bits] [file... ]
Invalid options were specified on the command line.
Usage: uncompress [-fv] [-c | -/] [file]...
Invalid options were specified on the command line.
Missing maxbits
Maxbits must follow -b, or invalid maxbits, not a
numeric value.
file: not in compressed format
The file specified to uncompress has not been
compressed.
file: compressed with xxbits, can only handle yybits
file was compressed by a program that could deal with
more bits than the compress code on this machine.
Recompress the file with smaller bits.
file: already has .Z suffix -- no change
The file is assumed to be already compressed. Rename the
file and try again.
file: already exists; do you wish to overwrite (y or n)?
Respond y if you want the output file to be replaced; n
if not.
uncompress: corrupt input
A SIGSEGV violation was detected, which usually means
that the input file is corrupted.
Compression:xx.xx%
Percentage of the input saved by compression. (Relevant
only for -v.)
- - not a regular file: unchanged
When the input file is not a regular file, (such as a
directory), it is left unaltered.
- - has xx other links: unchanged
The input file has links; it is left unchanged. See
ln(1) for more information.
- - file unchanged
No savings are achieved by compression. The input
remains uncompressed.
- -filename too long to tack on .Z
The path name is too long to append the .Z suffix.
- -cannot preserve extended attributes. file unchanged
Extended system attributes could not be copied.
Notes
Although compressed files are compatible between machines
with large memory, -b 12 should be used for file transfer to
architectures with a small process data space (64KB or
less).
compress should be more flexible about the existence of the
.Z suffix.