The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


uncompress - expand compressed data


uncompress [-cfv][file...]


The uncompress utility will restore files to their original state after they have been compressed using the compress utility. If no files are specified, the standard input will 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 are preserved.

This utility supports 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-dependent whether values of -b greater than 14 are supported.


The uncompress utility supports the XBD specification, Utility Syntax Guidelines  .

The following options are supported:

Write to standard output; no files will be changed.
Do not prompt for overwriting files. Except when run in the background, if -f is not given the user will 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 will write a diagnostic message to standard error and exit with a status greater than zero.
Write messages to standard error concerning the expansion of each file.


The following operand is supported:
A pathname of a file. If file already has the .Z suffix specified, it will be used as the input file and the output file will be named file with the .Z suffix removed. Otherwise, file will be used as the name of the output file and file with the .Z suffix appended will be used as the input file.


The standard input will be used only if no file operands are specified, or if a file operand is "-".


Input files are in the format produced by the compress utility.


The following environment variables affect the execution of uncompress:
Provide a default value for the internationalisation variables that are unset or null. If LANG is unset or null, the corresponding value from the implementation-dependent default locale will be used. If any of the internationalisation variables contains an invalid setting, the utility will behave as if none of the variables had been defined.
If set to a non-empty string value, override the values of all the other internationalisation variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single- 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 catalogues for the processing of LC_MESSAGES .




When there are no file operands or the -c option is specified, the uncompressed output will be written to standard output.


Prompts will be written to the standard error output under the conditions specified in the DESCRIPTION and OPTIONS sections. The prompts will contain the file pathname, but their format is otherwise unspecified. Otherwise, the standard error output will be used only for diagnostic messages.


Output files are the same as the respective input files to compress.




The following exit values are returned:
Successful completion.
An error occurred.


The input file will remain unmodified.


The limit of 14 on the compress -b bits argument is to achieve portability to all systems (within the restrictions imposed by the lack of an explicit published file format). Some systems based on 16-bit architectures cannot support 15- or 16-bit uncompression.






compress, unpack, zcat.

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Copyright © 1997 The Open Group
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