1pack(1) User Commands pack(1)
2
6 pack, pcat, unpack - compress and expand files
7
9 pack [-f/] [-] file...
10 pcat file...
13 unpack [-/] file...
16
19 pack
20 The pack command attempts to store the specified files in a compressed
21 form. Wherever possible (and useful), each input file file is replaced
22 by a packed file file.z with the same access modes, access and modified
23 dates, and owner as those of file. If pack is successful, file is
24 removed.
25 The amount of compression obtained depends on the size of the input
28 file and the character frequency distribution. Because a decoding tree
29 forms the first part of each .z file, it is usually not worthwhile to
30 pack files smaller than three blocks, unless the character frequency
31 distribution is very skewed, which can occur with printer plots or pic‐
32 tures.
33 Typically, text files are reduced to 60-75% of their original size.
36 Load modules, which use a larger character set and have a more uniform
37 distribution of characters, show little compression, the packed ver‐
38 sions being about 90% of the original size.
39 The pack utility returns a value that is the number of files that it
42 failed to compress. If that number exceeds 255, 255 is returned.
43 No packing occurs if:
46 o the file appears to be already packed
48 o the file name is too long to add the .z suffix
50 o the file has links
52 o the file is a directory
54 o the file cannot be opened
56 o the file is empty
58 o no disk storage blocks are saved by packing
60 o a file called file.z already exists
62 o the .z file cannot be created
64 o an I/O error occurred during processing.
66 The last segment of the file name must be short enough to allow space
69 for the appended .zextension. Directories cannot be compressed.
70 pcat
72 The pcat command does for packed files what cat(1) does for ordinary
73 files, except that pcat cannot be used as a filter. The specified files
74 are unpacked and written to the standard output.
75 pcat returns the number of files it was unable to unpack. Failure can
78 occur if:
79 o the file cannot be opened;
81 o the file does not appear to be the output of pack.
83 unpack
85 The unpack command expands files created by pack. For each file speci‐
86 fied in the command, a search is made for a file called file.z (or just
87 file, if file ends in .z). If this file appears to be a packed file, it
88 is replaced by its expanded version. The new file has the .z suffix
89 stripped from its name, and has the same access modes, access and modi‐
90 fication dates, and owner as those of the packed file.
91 unpack returns a value that is the number of files it was unable to
94 unpack. Failure can occur for the same reasons that it can in pcat, as
95 well as for the following:
96 o a file with the unpacked name already exists;
98 o the unpacked file cannot be created.
100
102 The following options are supported by pack:
103 -f Forces packing of file. This is useful for causing an entire
105 directory to be packed even if some of the files do not benefit.
106 Packed files can be restored to their original form using unpack
107 or pcat.
108 The following options are supported by pack and unpack:
112 -/ When packing or unpacking, copies any ACL and extended system
114 attributes associated with the source file to the target file. If
115 an ACL or extended system attributes cannot be copied, the origi‐
116 nal file is retained, a diagnostic message is written to stderr,
117 and the final exit status is non-zero.
118
121 The following operands are supported:
122 file A path name of a file to be packed, unpacked, or pcated; file
124 can include or omit the .z suffix.
125 − pack uses Huffman (minimum redundancy) codes on a byte-by-byte
128 basis. If the − argument is used, an internal flag is set that
129 causes the number of times each byte is used, its relative fre‐
130 quency, and the code for the byte to be printed on the standard
131 output. Additional occurrences of − in place of file causes the
132 internal flag to be set and reset.
133
136 See largefile(5) for the description of the behavior of pack, pcat, and
137 unpack when encountering files greater than or equal to 2 Gbyte ( 2^31
138 bytes).
139
141 Example 1 Viewing a Packed File
142 To view a packed file named file.z use:
145 example% pcat file.z
149 or just:
153 example% pcat file
157 Example 2 Making and Unpacked Copy:
160 To make an unpacked copy, say nnn, of a packed file named file.z (with‐
163 out destroying file.z) use the command:
164 example% pcat file >nnn
168
171 See environ(5) for descriptions of the following environment variables
172 that affect the execution of pack, pcat, and unpack: LC_CTYPE, LC_MES‐
173 SAGES, and NLSPATH.
174
176 The following exit values are returned:
177 0 Successful completion.
179 >0 An error occurred. The number of files the command failed to
182 pack/unpack is returned. If the number of failures exceeds 255,
183 then 255 is returned.
184
187 See attributes(5) for descriptions of the following attributes:
188 ┌─────────────────────────────┬─────────────────────────────┐
193 │ATTRIBUTE TYPE │ATTRIBUTE VALUE │
194 ├─────────────────────────────┼─────────────────────────────┤
195 │Availability │SUNWesu │
196 ├─────────────────────────────┼─────────────────────────────┤
197 │CSI │Enabled │
198 └─────────────────────────────┴─────────────────────────────┘
199
201 cat(1), compress(1), zcat(1), fgetattr(3C), fsetattr(3C)attributes(5),
202 environ(5), largefile(5)
203SunOS 5.11 13 Mar 2008 pack(1)