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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
uudecode — decode a binary file
SYNOPSIS
uudecode [−o outfile] [file]
DESCRIPTION
The uudecode utility shall read a file, or standard input if no file is specified, that includes data
created by the uuencode utility. The uudecode utility shall scan the input file, searching for data
compatible with one of the formats specified in uuencode, and attempt to create or overwrite the file
described by the data (or overridden by the −o option). The pathname shall be contained in the data or
specified by the −o option. The file access permission bits and contents for the file to be produced
shall be contained in that data. The mode bits of the created file (other than standard output) shall be
set from the file access permission bits contained in the data; that is, other attributes of the mode,
including the file mode creation mask (see umask), shall not affect the file being produced. If either of
the op characters '+' and '−' (see chmod) are specified in symbolic mode, the initial mode on which those
operations are based is unspecified.
If the pathname of the file to be produced exists, and the user does not have write permission on that
file, uudecode shall terminate with an error. If the pathname of the file to be produced exists, and the
user has write permission on that file, the existing file shall be overwritten.
If the input data was produced by uuencode on a system with a different number of bits per byte than on
the target system, the results of uudecode are unspecified.
OPTIONS
The uudecode utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility
Syntax Guidelines.
The following option shall be supported by the implementation:
−o outfile
A pathname of a file that shall be used instead of any pathname contained in the input data.
Specifying an outfile option-argument of /dev/stdout shall indicate standard output.
OPERANDS
The following operand shall be supported:
file The pathname of a file containing the output of uuencode.
STDIN
See the INPUT FILES section.
INPUT FILES
The input files shall be files containing the output of uuencode.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of uudecode:
LANG Provide a default value for the internationalization variables that are unset or null. (See the
Base Definitions volume of POSIX.1‐2008, Section 8.2, Internationalization Variables for the
precedence of internationalization variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of all the other internationalization
variables.
LC_CTYPE 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 and input files).
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diagnostic
messages written to standard error.
NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.
ASYNCHRONOUS EVENTS
Default.
STDOUT
If the file data header encoded by uuencode is − or /dev/stdout, or the −o /dev/stdout option overrides
the file data, the standard output shall be in the same format as the file originally encoded by
uuencode. Otherwise, the standard output shall not be used.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
The output file shall be in the same format as the file originally encoded by uuencode.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The user who is invoking uudecode must have write permission on any file being created.
The output of uuencode is essentially an encoded bit stream that is not cognizant of byte boundaries. It
is possible that a 9-bit byte target machine can process input from an 8-bit source, if it is aware of
the requirement, but the reverse is unlikely to be satisfying. Of course, the only data that is
meaningful for such a transfer between architectures is generally character data.
EXAMPLES
None.
RATIONALE
Input files are not necessarily text files, as stated by an early proposal. Although the uuencode output
is a text file, that output could have been wrapped within another file or mail message that is not a
text file.
The −o option is not historical practice, but was added at the request of WG15 so that the user could
override the target pathname without having to edit the input data itself.
In early drafts, the [−o outfile] option-argument allowed the use of − to mean standard output. The
symbol − has only been used previously in POSIX.1‐2008 as a standard input indicator. The standard
developers did not wish to overload the meaning of − in this manner. The /dev/stdout concept exists on
most modern systems. The /dev/stdout syntax does not refer to a new special file. It is just a magic
cookie to specify standard output.
FUTURE DIRECTIONS
None.
SEE ALSO
chmod, umask, uuencode
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment Variables, Section 12.2, Utility
Syntax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .