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All Rights Reserved 46 .\" 47 .TH PACK 1 "Mar 13, 2008" 48 .SH NAME 49 pack, pcat, unpack \- compress and expand files 50 .SH SYNOPSIS 51 .LP 52 .nf 53 \fBpack\fR [\fB-f/\fR] [\fB-\fR] \fIfile\fR... 54 .fi 55 56 .LP 57 .nf 58 \fBpcat\fR \fIfile\fR... 59 .fi 60 61 .LP 62 .nf 63 \fBunpack\fR [\fB-/\fR] \fIfile\fR... 64 .fi 65 66 .SH DESCRIPTION 67 .SS "pack" 68 .sp 69 .LP 70 The \fBpack\fR command attempts to store the specified files in a compressed 71 form. Wherever possible (and useful), each input file \fBfile\fR is replaced by 72 a packed file \fBfile\fR\fB\&.z\fR with the same access modes, access and 73 modified dates, and owner as those of \fBfile\fR. If \fBpack\fR is successful, 74 \fBfile\fR is removed. 75 .sp 76 .LP 77 The amount of compression obtained depends on the size of the input file and 78 the character frequency distribution. Because a decoding tree forms the first 79 part of each \fB\&.z\fR file, it is usually not worthwhile to pack files 80 smaller than three blocks, unless the character frequency distribution is very 81 skewed, which can occur with printer plots or pictures. 82 .sp 83 .LP 84 Typically, text files are reduced to 60-75% of their original size. Load 85 modules, which use a larger character set and have a more uniform distribution 86 of characters, show little compression, the packed versions being about 90% of 87 the original size. 88 .sp 89 .LP 90 The \fBpack\fR utility returns a value that is the number of files that it 91 failed to compress. If that number exceeds \fB255\fR, \fB255\fR is returned. 92 .sp 93 .LP 94 No packing occurs if: 95 .RS +4 96 .TP 97 .ie t \(bu 98 .el o 99 the file appears to be already packed 100 .RE 101 .RS +4 102 .TP 103 .ie t \(bu 104 .el o 105 the file name is too long to add the \fB\&.z\fR suffix 106 .RE 107 .RS +4 108 .TP 109 .ie t \(bu 110 .el o 111 the file has links 112 .RE 113 .RS +4 114 .TP 115 .ie t \(bu 116 .el o 117 the file is a directory 118 .RE 119 .RS +4 120 .TP 121 .ie t \(bu 122 .el o 123 the file cannot be opened 124 .RE 125 .RS +4 126 .TP 127 .ie t \(bu 128 .el o 129 the file is empty 130 .RE 131 .RS +4 132 .TP 133 .ie t \(bu 134 .el o 135 no disk storage blocks are saved by packing 136 .RE 137 .RS +4 138 .TP 139 .ie t \(bu 140 .el o 141 a file called \fBfile\fR\fB\&.z\fR already exists 142 .RE 143 .RS +4 144 .TP 145 .ie t \(bu 146 .el o 147 the \fB\&.z\fR file cannot be created 148 .RE 149 .RS +4 150 .TP 151 .ie t \(bu 152 .el o 153 an I/O error occurred during processing. 154 .RE 155 .sp 156 .LP 157 The last segment of the file name must be short enough to allow space for the 158 appended \fB\&.z\fRextension. Directories cannot be compressed. 159 .SS "pcat" 160 .sp 161 .LP 162 The \fBpcat\fR command does for packed files what \fBcat\fR(1) does for 163 ordinary files, except that \fBpcat\fR cannot be used as a filter. The 164 specified files are unpacked and written to the standard output. 165 .sp 166 .LP 167 \fBpcat\fR returns the number of files it was unable to unpack. Failure can 168 occur if: 169 .RS +4 170 .TP 171 .ie t \(bu 172 .el o 173 the file cannot be opened; 174 .RE 175 .RS +4 176 .TP 177 .ie t \(bu 178 .el o 179 the file does not appear to be the output of \fBpack\fR. 180 .RE 181 .SS "unpack" 182 .sp 183 .LP 184 The \fBunpack\fR command expands files created by \fBpack\fR. For each 185 \fBfile\fR specified in the command, a search is made for a file called 186 \fBfile\fR\fB\&.z\fR (or just \fBfile\fR, if \fBfile\fR ends in \fB\&.z\fR). If 187 this file appears to be a packed file, it is replaced by its expanded version. 188 The new file has the \fB\&.z\fR suffix stripped from its name, and has the same 189 access modes, access and modification dates, and owner as those of the packed 190 file. 191 .sp 192 .LP 193 \fBunpack\fR returns a value that is the number of files it was unable to 194 unpack. Failure can occur for the same reasons that it can in \fBpcat\fR, as 195 well as for the following: 196 .RS +4 197 .TP 198 .ie t \(bu 199 .el o 200 a file with the unpacked name already exists; 201 .RE 202 .RS +4 203 .TP 204 .ie t \(bu 205 .el o 206 the unpacked file cannot be created. 207 .RE 208 .SH OPTIONS 209 .sp 210 .LP 211 The following options are supported by \fBpack\fR: 212 .sp 213 .ne 2 214 .na 215 \fB\fB-f\fR\fR 216 .ad 217 .RS 6n 218 Forces packing of \fBfile\fR. This is useful for causing an entire directory to 219 be packed even if some of the files do not benefit. Packed files can be 220 restored to their original form using \fBunpack\fR or \fBpcat\fR. 221 .RE 222 223 .sp 224 .LP 225 The following options are supported by \fBpack\fR and \fBunpack\fR: 226 .sp 227 .ne 2 228 .na 229 \fB\fB-/\fR\fR 230 .ad 231 .RS 6n 232 When packing or unpacking, copies any ACL and extended system attributes 233 associated with the source file to the target file. If an ACL or extended 234 system attributes cannot be copied, the original file is retained, a diagnostic 235 message is written to \fBstderr\fR, and the final exit status is 236 \fBnon-zero\fR. 237 .RE 238 239 .SH OPERANDS 240 .sp 241 .LP 242 The following operands are supported: 243 .sp 244 .ne 2 245 .na 246 \fB\fBfile\fR\fR 247 .ad 248 .RS 8n 249 A path name of a file to be packed, unpacked, or pcated; \fBfile\fR can include 250 or omit the \fB\&.z\fR suffix. 251 .RE 252 253 .sp 254 .ne 2 255 .na 256 \fB\fB\(mi\fR\fR 257 .ad 258 .RS 8n 259 \fBpack\fR uses Huffman (minimum redundancy) codes on a byte-by-byte basis. If 260 the \fB\(mi\fR argument is used, an internal flag is set that causes the number 261 of times each byte is used, its relative frequency, and the code for the byte 262 to be printed on the standard output. Additional occurrences of \fB\(mi\fR in 263 place of \fBfile\fR causes the internal flag to be set and reset. 264 .RE 265 266 .SH USAGE 267 .sp 268 .LP 269 See \fBlargefile\fR(5) for the description of the behavior of \fBpack\fR, 270 \fBpcat\fR, and \fBunpack\fR when encountering files greater than or equal to 2 271 Gbyte ( 2^31 bytes). 272 .SH EXAMPLES 273 .LP 274 \fBExample 1 \fRViewing a Packed File 275 .sp 276 .LP 277 To view a packed file named \fBfile.z\fR use: 278 279 .sp 280 .LP 281 \fBexample%\fR \fBpcat\fR \fBfile.z\fR 282 283 .sp 284 .LP 285 or just: 286 287 .sp 288 .LP 289 \fBexample%\fR \fBpcat\fR \fBfile\fR 290 291 .LP 292 \fBExample 2 \fRMaking and Unpacked Copy: 293 .sp 294 .LP 295 To make an unpacked copy, say \fBnnn\fR, of a packed file named \fBfile.z\fR 296 (without destroying \fBfile.z\fR) use the command: 297 298 .sp 299 .LP 300 \fBexample%\fR \fBpcat\fR \fBfile\fR \fB>nnn\fR 301 302 .SH ENVIRONMENT VARIABLES 303 .sp 304 .LP 305 See \fBenviron\fR(5) for descriptions of the following environment variables 306 that affect the execution of \fBpack\fR, \fBpcat\fR, and \fBunpack\fR: 307 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR. 308 .SH EXIT STATUS 309 .sp 310 .LP 311 The following exit values are returned: 312 .sp 313 .ne 2 314 .na 315 \fB\fB0\fR\fR 316 .ad 317 .RS 6n 318 Successful completion. 319 .RE 320 321 .sp 322 .ne 2 323 .na 324 \fB\fB>0\fR\fR 325 .ad 326 .RS 6n 327 An error occurred. The number of files the command failed to pack/unpack is 328 returned. If the number of failures exceeds \fB255\fR, then \fB255\fR is 329 returned. 330 .RE 331 332 .SH ATTRIBUTES 333 .sp 334 .LP 335 See \fBattributes\fR(5) for descriptions of the following attributes: 336 .sp 337 338 .sp 339 .TS 340 box; 341 c | c 342 l | l . 343 ATTRIBUTE TYPE ATTRIBUTE VALUE 344 _ 345 CSI Enabled 346 .TE 347 348 .SH SEE ALSO 349 .sp 350 .LP 351 \fBcat\fR(1), \fBcompress\fR(1), \fBzcat\fR(1), \fBfgetattr\fR(3C), 352 \fBfsetattr\fR(3C), \fBattributes\fR(5), \fBenviron\fR(5), \fBlargefile\fR(5)