unpack - Decode Huffman-packed files

Format

unpack file...

Note: The unpack utility is fully supported for compatibility with older UNIX systems. However, it is recommended that the uncompress utility be used instead because it might provide greater functionality and is considered the standard for portable UNIX applications as defined by POSIX.2 IEEE standard 1003.2-1992.

Description

unpack uncompresses files compressed by pack, using a Huffman minimal redundancy code. By default, unpack looks for file with a .z extension. It places the decompressed output in a file with the same name, but without the extension. The owner, permissions, and times of last access and last modification are also preserved. Packed files can be identified by file. You can use pcat to view packed text files without unpacking them in place.

unpack does not unpack a file if:
  • The file name is too long after the .z is removed.
  • The input file cannot be opened.
  • An existing file has the same name as the output file.
  • The output file can't be created.
  • The input file doesn't appear to have been created by pack.

Localization

unpack uses the following localization environment variables:
  • LANG
  • LC_ALL
  • LC_COLLATE
  • LC_CTYPE
  • LC_MESSAGES
  • NLSPATH

Files

unpack uses the following file:
pk$*
Temporary copy of input file. (You might see this in the current directory if unpack is interrupted.) The file is in the same directory as the file being unpacked.

Exit values

0
Successful completion
n
Indicates that files might not be unpacked properly. For example, if three out of six files might not be unpacked properly, the exit status is 3.
Possible reasons for failure include:
  • Unknown command-line option.
  • Error creating a name for a temporary file.
  • Error opening an input file or a temporary file.
  • Error writing to a temporary file.
  • Inability to rename a temporary file.
  • Inability to restore the modification time on a packed file.
  • Input file was not packed.
  • A packed file is corrupted.

Messages

Possible error messages include:
file: Not a packed file
pack did not process the file. In this case, the file is not changed.

Portability

POSIX.2, X/Open Portability Guide, UNIX systems.

Related information

file, pack, pcat