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compress [-fv/] [-b bits] [file]...
compress -c [-fv] [-b bits] [file]
uncompress [-fv] [-c | -/] [file]...
zcat [file]...
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 parameter 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.
This utility supports the uncompressing of any files produced by compress. For files produced by compress on other systems, uncompress supports 9- to 16-bit compression (see -b).
Sets the upper limit (in bits) for common substring codes. bits must be between 9 and 16 (16 is the default). Lowering the number of bits result in larger, less compressed files.
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'.
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 process 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.
Verbose. Writes to standard error messages concerning 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 attributes cannot be copied, the original file is retained, a diagnostic is written to stderr, and the final exit status is non-zero.
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.
Affirmative responses are processed using the extended regular expression defined for the yesexpr keyword in the LC_MESSAGES category of the user's locale. The locale specified 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 characters, the behavior of character classes used in the expression defined for the yesexpr. See locale(7).
Successful completion.
An error occurred.
One or more files were not compressed because they would have increased in size (and the -f option was not specified).
An error occurred.
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| CSI Enabled |
| Interface Stability Committed |
| Standard See standards(7). |
compress c [-fv] [-b maxbits] [file]
Invalid options were specified on the command line.
Invalid options were specified on the command line.
Maxbits must follow -b, or invalid maxbits, not a numeric value.
The file specified to uncompress has not been compressed.
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.
The file is assumed to be already compressed. Rename the file and try again.
Respond y if you want the output file to be replaced; n if not.
A SIGSEGV violation was detected, which usually means that the input file is corrupted.
Percentage of the input saved by compression. (Relevant only for -v.)
When the input file is not a regular file, (such as a directory), it is left unaltered.
The input file has links; it is left unchanged. See ln(1) for more information.
No savings are achieved by compression. The input remains uncompressed.
The path name is too long to append the .Z suffix.
Extended system attributes could not be copied.
compress should be more flexible about the existence of the .\|Z suffix.