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SunOS man pages : unpack (1)

User Commands                                             pack(1)

NAME

pack, pcat, unpack - compress and expand files

SYNOPSIS

pack [ -f ] [ - ] file ... pcat file ... unpack file ...

DESCRIPTION

pack The pack command attempts to store the specified files in a compressed form. Wherever possible (and useful), each input file file is replaced by a packed file file.z with the same access modes, access and modified dates, and owner as those of file. If pack is successful, file will be removed. The amount of compression obtained depends on the size of the input file and the character frequency distribution. Because a decoding tree forms the first part of each .z file, it is usually not worthwhile to pack files smaller than three blocks, unless the character frequency distribu- tion is very skewed, which may occur with printer plots or pictures. Typically, text files are reduced to 60-75% of their origi- nal size. Load modules, which use a larger character set and have a more uniform distribution of characters, show little compression, the packed versions being about 90% of the ori- ginal size. pack returns a value that is the number of files that it failed to compress. No packing will occur if: o the file appears to be already packed o the file name has more than 14 - 2 bytes o the file has links o the file is a directory o the file cannot be opened o the file is empty o no disk storage blocks will be saved by packing o a file called file.z already exists SunOS 5.8 Last change: 20 Dec 1996 1 User Commands pack(1) o the .z file cannot be created o an I/O error occurred during processing. The last segment of the file name must contain no more than 14 - 2 bytes to allow space for the appended .z extension. Directories cannot be compressed. pcat The pcat command does for packed files what cat(1) does for ordinary files, except that pcat cannot be used as a filter. The specified files are unpacked and written to the standard output. pcat returns the number of files it was unable to unpack. Failure may occur if: o the file cannot be opened; o the file does not appear to be the output of pack. unpack The unpack command expands files created by pack. For each file specified in the command, a search is made for a file called file.z (or just file, if file ends in .z). If this file appears to be a packed file, it is replaced by its expanded version. The new file has the .z suffix stripped from its name, and has the same access modes, access and modification dates, and owner as those of the packed file. unpack returns a value that is the number of files it was unable to unpack. Failure may occur for the same reasons that it may in pcat, as well as for the following: o a file with the ``unpacked'' name already exists; o the unpacked file cannot be created. o the filename (excluding the .z extension) has more than 14 bytes.

OPTIONS

The following options are supported by pack: -f Forces packing of file. This is useful for causing an entire directory to be packed even if some of the files will not benefit. Packed files can be restored to their original form using unpack or pcat.

OPERANDS

The following operands are supported: SunOS 5.8 Last change: 20 Dec 1996 2 User Commands pack(1) file A path name of a file to be packed, unpacked, or pcated; file can include or omit the .z suffix. - pack uses Huffman (minimum redundancy) codes on a byte-by-byte basis. If the - argument is used, an internal flag is set that causes the number of times each byte is used, its relative frequency, and the code for the byte to be printed on the standard out- put. Additional occurrences of - in place of file will cause the internal flag to be set and reset.

USAGE

See largefile(5) for the description of the behavior of pack, pcat, and unpack when encountering files greater than or equal to 2 Gbyte ( 2**31 bytes).

EXAMPLES

Example 1: Viewing a Packed File To view a packed file named file.z use: example% pcat file.z or just: example% pcat file Example 2: Making and Unpacked Copy: To make an unpacked copy, say nnn, of a packed file named file.z (without destroying file.z) use the command: example% pcat file >nnn

ENVIRONMENT VARIABLES

See environ(5) for descriptions of the following environment variables that affect the execution of pack, pcat, and unpack: LC_CTYPE, LC_MESSAGES, and NLSPATH.

EXIT STATUS

The following exit values are returned: 0 Successful completion. >0 An error occurred. The number of files the command failed to pack/unpack is returned.

ATTRIBUTES

See attributes(5) for descriptions of the following attri- butes: SunOS 5.8 Last change: 20 Dec 1996 3 User Commands pack(1) ____________________________________________________________ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |_____________________________|_____________________________| | Availability | SUNWesu | |_____________________________|_____________________________| | CSI | Enabled | |_____________________________|_____________________________|

SEE ALSO

cat(1), compress(1), zcat(1), attributes(5), environ(5), largefile( 5) SunOS 5.8 Last change: 20 Dec 1996 4