The uncompress utility shall restore files to their original state after
they have been compressed using the compress utility. If no files are
specified, the standard input shall be uncompressed to the standard output. If
the invoking process has appropriate privileges, the ownership, modes, access
time, and modification time of the original file shall be preserved.
This utility shall support the uncompressing of any files produced by the
compress utility on the same implementation. For files produced by
compress on other systems, uncompress supports 9 to 14-bit
compression (see compress , -b); it is implementation-defined
whether values of -b greater than 14 are supported.
The uncompress utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
Write to standard output; no files are changed.
Do not prompt for overwriting files. Except when run in the
background, if -f is not given the user shall be prompted as to
whether an existing file should be overwritten. If the standard input is
not a terminal and -f is not given, uncompress shall write a
diagnostic message to standard error and exit with a status greater than
Write messages to standard error concerning the expansion
of each file.
A pathname of a file. If file already has the
.Z suffix specified, it shall be used as the input file and the
output file shall be named file with the .Z suffix removed.
Otherwise, file shall be used as the name of the output file and
file with the .Z suffix appended shall be used as the input
The following environment variables shall affect the execution of
Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
If set to a non-empty string value, override the values of
all the other internationalization variables.
Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments).
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to standard error.
Determine the location of message catalogs for the
processing of LC_MESSAGES.
Prompts shall be written to the standard error output under the conditions
specified in the DESCRIPTION and OPTIONS sections. The prompts shall contain
the file pathname, but their format is otherwise unspecified.
Otherwise, the standard error output shall be used only for diagnostic
The limit of 14 on the compress-bbits argument is to
achieve portability to all systems (within the restrictions imposed by the
lack of an explicit published file format). Some implementations based on
16-bit architectures cannot support 15 or 16-bit uncompression.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html