8
9 SYNOPSIS
10 compress [-fv/] [-b bits] [file]...
11
12
13 compress -c [-fv] [-b bits] [file]
14
15
16 uncompress [-fv] [-c | -/] [file]...
17
18
19 zcat [file]...
20
21
22 DESCRIPTION
23 compress
24 The compress utility attempts to reduce the size of the named files by
25 using adaptive Lempel-Ziv coding. Except when the output is to the
26 standard output, each file is replaced by one with the extension .Z,
27 while keeping the same ownership modes, change times and modification
28 times, ACLs, and extended attributes. The compress utility also attempt
29 to set the owner and group of file.z to the owner and group of file,
30 but does not fail if this cannot be done. If appending the .Z to the
31 file pathname would make the pathname exceed 1023 bytes, the command
32 fails. If no files are specified, the standard input is compressed to
33 the standard output.
34
35
36 The amount of compression obtained depends on the size of the input,
37 the number of bits per code, and the distribution of common substrings.
38 Typically, text such as source code or English is reduced by 50-60%.
39 Compression is generally much better than that achieved by Huffman
40 coding (as used in pack(1)) and it takes less time to compute. The bits
41 parameter specified during compression is encoded within the compressed
42 file, along with a magic number to ensure that neither decompression of
43 random data nor recompression of compressed data is subsequently
44 allowed.
45
46 uncompress
47 The uncompress utility restores files to their original state after
48 they have been compressed using the compress utility. If no files are
49 specified, the standard input is uncompressed to the standard output.
50
51
52 This utility supports the uncompressing of any files produced by
53 compress. For files produced by compress on other systems, uncompress
54 supports 9- to 16-bit compression (see -b).
55
56 zcat
57 The zcat utility writes to standard output the uncompressed form of
58 files that have been compressed using compress. It is the equivalent of
59 uncompress-c. Input files are not affected.
60
61 OPTIONS
62 The following options are supported:
63
64 -b bits
65 Sets the upper limit (in bits) for common substring codes.
66 bits must be between 9 and 16 (16 is the default). Lowering
67 the number of bits result in larger, less compressed files.
68
69
70 -c
71 Writes to the standard output; no files are changed and no
72 .Z files are created. The behavior of zcat is identical to
73 that of `uncompress -c'.
74
75
76 -f
77 When compressing, forces compression of file, even if it
78 does not actually reduce the size of the file, or if the
79 corresponding file.Z file already exists.
103 associated with extended attributes of the source file to
104 the corresponding extended attributes associated with the
105 target file. If any extended system attributes cannot be
106 copied, the original file is retained, a diagnostic is
107 written to stderr, and the final exit status is non-zero.
108
109
110 OPERANDS
111 The following operand is supported:
112
113 file
114 A path name of a file to be compressed by compress,
115 uncompressed by uncompress, or whose uncompressed form is
116 written to standard out by zcat. If file is -, or if no file is
117 specified, the standard input is used.
118
119
120 USAGE
121 See largefile(5) for the description of the behavior of compress,
122 uncompress, and zcat when encountering files greater than or equal to 2
123 Gbyte ( 2^31 bytes).
124
125 ENVIRONMENT VARIABLES
126 See environ(5) for descriptions of the following environment variables
127 that affect the execution of compress, uncompress, and zcat: LANG,
128 LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.
129
130
131 Affirmative responses are processed using the extended regular
132 expression defined for the yesexpr keyword in the LC_MESSAGES category
133 of the user's locale. The locale specified in the LC_COLLATE category
134 defines the behavior of ranges, equivalence classes, and multi-
135 character collating elements used in the expression defined for
136 yesexpr. The locale specified in LC_CTYPE determines the locale for
137 interpretation of sequences of bytes of text data a characters, the
138 behavior of character classes used in the expression defined for the
139 yesexpr. See locale(5).
140
141 EXIT STATUS
142 The following error values are returned:
143
162 See attributes(5) for descriptions of the following attributes:
163
164
165
166
167 +--------------------+-------------------+
168 | ATTRIBUTE TYPE | ATTRIBUTE VALUE |
169 +--------------------+-------------------+
170 |CSI | Enabled |
171 +--------------------+-------------------+
172 |Interface Stability | Committed |
173 +--------------------+-------------------+
174 |Standard | See standards(5). |
175 +--------------------+-------------------+
176
177 SEE ALSO
178 ln(1), pack(1), fgetattr(3C), fsetattr(3C), attributes(5), environ(5),
179 largefile(5), locale(5), standards(5)
180
181 DIAGNOSTICS
182 Usage: compress [-fv/] [-b bits] [file... ]
183 compress c [-fv] [-b bits] [file... ]
184
185 Invalid options were specified on the command line.
186
187
188 Usage: uncompress [-fv] [-c | -/] [file]...
189
190 Invalid options were specified on the command line.
191
192
193 Missing maxbits
194
195 Maxbits must follow -b, or invalid maxbits, not a numeric value.
196
197
198 file: not in compressed format
199
200 The file specified to uncompress has not been compressed.
201
202
203 file: compressed with xxbits, can only handle yybits
204
205 file was compressed by a program that could deal with more bits
206 than the compress code on this machine. Recompress the file with
207 smaller bits.
208
209
210 file: already has .Z suffix -- no change
211
212 The file is assumed to be already compressed. Rename the file and
213 try again.
214
215
216 file: already exists; do you wish to overwrite (y or n)?
217
218 Respond y if you want the output file to be replaced; n if not.
219
220
221 uncompress: corrupt input
222
223 A SIGSEGV violation was detected, which usually means that the
224 input file is corrupted.
225
226
227 Compression:xx.xx%
228
229 Percentage of the input saved by compression. (Relevant only for
230 -v.)
231
232
233 - - not a regular file: unchanged
234
235 When the input file is not a regular file, (such as a directory),
236 it is left unaltered.
251 - -filename too long to tack on .Z
252
253 The path name is too long to append the .Z suffix.
254
255
256 - -cannot preserve extended attributes. file unchanged
257
258 Extended system attributes could not be copied.
259
260
261 NOTES
262 Although compressed files are compatible between machines with large
263 memory, -b 12 should be used for file transfer to architectures with a
264 small process data space (64KB or less).
265
266
267 compress should be more flexible about the existence of the .Z suffix.
268
269
270
271 March 13, 2008 COMPRESS(1)
|
8
9 SYNOPSIS
10 compress [-fv/] [-b bits] [file]...
11
12
13 compress -c [-fv] [-b bits] [file]
14
15
16 uncompress [-fv] [-c | -/] [file]...
17
18
19 zcat [file]...
20
21
22 DESCRIPTION
23 compress
24 The compress utility attempts to reduce the size of the named files by
25 using adaptive Lempel-Ziv coding. Except when the output is to the
26 standard output, each file is replaced by one with the extension .Z,
27 while keeping the same ownership modes, change times and modification
28 times, ACLs, and extended attributes. The compress utility also
29 attempts to set the owner and group of file.Z to the owner and group of
30 file, but does not fail if this cannot be done. If appending the .Z to
31 the file pathname would make the pathname exceed 1023 bytes, the
32 command fails. If no files are specified, the standard input is
33 compressed to the standard output.
34
35
36 The amount of compression obtained depends on the size of the input,
37 the number of bits per code, and the distribution of common substrings.
38 Typically, text such as source code or English is reduced by 50-60%.
39 Compression is generally much better than that achieved by Huffman
40 coding (as used in pack(1)) and it takes less time to compute. The bits
41 parameter specified during compression is encoded within the compressed
42 file, along with a magic number to ensure that neither decompression of
43 random data nor recompression of compressed data is subsequently
44 allowed.
45
46 uncompress
47 The uncompress utility restores files to their original state after
48 they have been compressed using the compress utility. If no files are
49 specified, the standard input is uncompressed to the standard output.
50
51
52 This utility supports the uncompressing of any files produced by
53 compress. For files produced by compress on other systems, uncompress
54 supports 9- to 16-bit compression (see -b).
55
56 zcat
57 The zcat utility writes to standard output the uncompressed form of
58 files that have been compressed using compress. It is the equivalent of
59 uncompress -c. Input files are not affected.
60
61 OPTIONS
62 The following options are supported:
63
64 -b bits
65 Sets the upper limit (in bits) for common substring codes.
66 bits must be between 9 and 16 (16 is the default). Lowering
67 the number of bits result in larger, less compressed files.
68
69
70 -c
71 Writes to the standard output; no files are changed and no
72 .Z files are created. The behavior of zcat is identical to
73 that of `uncompress -c'.
74
75
76 -f
77 When compressing, forces compression of file, even if it
78 does not actually reduce the size of the file, or if the
79 corresponding file.Z file already exists.
103 associated with extended attributes of the source file to
104 the corresponding extended attributes associated with the
105 target file. If any extended system attributes cannot be
106 copied, the original file is retained, a diagnostic is
107 written to stderr, and the final exit status is non-zero.
108
109
110 OPERANDS
111 The following operand is supported:
112
113 file
114 A path name of a file to be compressed by compress,
115 uncompressed by uncompress, or whose uncompressed form is
116 written to standard out by zcat. If file is -, or if no file is
117 specified, the standard input is used.
118
119
120 USAGE
121 See largefile(5) for the description of the behavior of compress,
122 uncompress, and zcat when encountering files greater than or equal to 2
123 Gbyte (2^31 bytes).
124
125 ENVIRONMENT VARIABLES
126 See environ(5) for descriptions of the following environment variables
127 that affect the execution of compress, uncompress, and zcat: LANG,
128 LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.
129
130
131 Affirmative responses are processed using the extended regular
132 expression defined for the yesexpr keyword in the LC_MESSAGES category
133 of the user's locale. The locale specified in the LC_COLLATE category
134 defines the behavior of ranges, equivalence classes, and multi-
135 character collating elements used in the expression defined for
136 yesexpr. The locale specified in LC_CTYPE determines the locale for
137 interpretation of sequences of bytes of text data a characters, the
138 behavior of character classes used in the expression defined for the
139 yesexpr. See locale(5).
140
141 EXIT STATUS
142 The following error values are returned:
143
162 See attributes(5) for descriptions of the following attributes:
163
164
165
166
167 +--------------------+-------------------+
168 | ATTRIBUTE TYPE | ATTRIBUTE VALUE |
169 +--------------------+-------------------+
170 |CSI | Enabled |
171 +--------------------+-------------------+
172 |Interface Stability | Committed |
173 +--------------------+-------------------+
174 |Standard | See standards(5). |
175 +--------------------+-------------------+
176
177 SEE ALSO
178 ln(1), pack(1), fgetattr(3C), fsetattr(3C), attributes(5), environ(5),
179 largefile(5), locale(5), standards(5)
180
181 DIAGNOSTICS
182 Usage: compress [-fv/] [-b maxbits] [file... ]
183 compress c [-fv] [-b maxbits] [file]
184
185 Invalid options were specified on the command line.
186
187
188 Usage: uncompress [-fv] [-c | -/] [file]...
189
190 Invalid options were specified on the command line.
191
192
193 Missing maxbits
194
195 Maxbits must follow -b, or invalid maxbits, not a numeric value.
196
197
198 file: not in compressed format
199
200 The file specified to uncompress has not been compressed.
201
202
203 file: compressed with xxbits, can only handle yybits
204
205 file was compressed by a program that could deal with more bits
206 than the compress code on this machine. Recompress the file with
207 smaller bits.
208
209
210 file: already has .Z suffix -- no change
211
212 The file is assumed to be already compressed. Rename the file and
213 try again.
214
215
216 file already exists; do you wish to overwrite (yes or no)?
217
218 Respond y if you want the output file to be replaced; n if not.
219
220
221 uncompress: corrupt input
222
223 A SIGSEGV violation was detected, which usually means that the
224 input file is corrupted.
225
226
227 Compression:xx.xx%
228
229 Percentage of the input saved by compression. (Relevant only for
230 -v.)
231
232
233 - - not a regular file: unchanged
234
235 When the input file is not a regular file, (such as a directory),
236 it is left unaltered.
251 - -filename too long to tack on .Z
252
253 The path name is too long to append the .Z suffix.
254
255
256 - -cannot preserve extended attributes. file unchanged
257
258 Extended system attributes could not be copied.
259
260
261 NOTES
262 Although compressed files are compatible between machines with large
263 memory, -b 12 should be used for file transfer to architectures with a
264 small process data space (64KB or less).
265
266
267 compress should be more flexible about the existence of the .Z suffix.
268
269
270
271 February 5, 2020 COMPRESS(1)
|