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UUDECODE(1P) POSIX Programmer's Manual UUDECODE(1P)

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (con-
sult 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 stan-
dard 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 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 sys-
tem, the results of uudecode are unspecified.

OPTIONS
The uudecode utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of international-
ization 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 stan-
dard 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 out-
put 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 gen-
erally 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 IEEE Std 1003.1-2001 as a standard input indicator. The developers of the standard did not wish
to overload the meaning of - in this manner. The /dev/stdout concept exists on most modern systems. The /dev/stdout syn-
tax does not refer to a new special file. It is just a magic cookie to specify standard output.

FUTURE DIRECTIONS
None.