base64: encode and decode base64 files
This page describes, in Unix manual page style,
a program
available for downloading from this site
which encodes binary files in the "Base64" format used by
MIME-encoded documents such as electronic mail messages with
embedded images and audio files.
NAME
base64 - encode and decode base64 files
SYNOPSIS
base64 [ -d ] [ -e ]
[ -n ]
[ -u ] [ infile ] [ outfile ]
DESCRIPTION
The MIME (Multipurpose Internet Mail Extensions) specification
(RFC
1341 and successors) defines a mechanism for encoding arbitrary binary
information for transmission by electronic mail. Triplets of 8-bit
octets are encoded as groups of four characters, each representing 6
bits of the source 24 bits. Only characters present in all variants
of ASCII and EBCDIC are used, avoiding incompatibilities in other
forms of encoding such as uuencode/uudecode.
base64
is a command line utility which encodes and decodes files in this format.
It can be used within a pipeline as an encoding or decoding filter,
and is most commonly used in this manner as part of an automated
mail processing system.
OPTIONS
- -d
-
Decodes the input, previously created by
base64,
to recover the original input file.
- -e
-
Encodes the input into an output text file containing
its base64 encoding.
- -n
-
Suppress error checking when decoding. By default, upon encountering
a non white space character which does not belong to the base64
set, or discovering the input file is incorrectly padded to a
multiple of four characters, base64 issues an error
message and terminates
processing with exit status 1. The
-n
option suppresses even this rudimentary error checking; invalid
characters are silently ignored and the output truncated to the
last three valid octets if the input is incorrectly padded.
- -u
- Print how to call information and a summary of
options.
EXIT STATUS
base64
returns status 0 if processing was completed without errors, 1 if an
I/O error occurred or errors were detected in decoding a file which
indicate it is incorrect or incomplete, and 2 if processing
could not be performed at all due, for example, to a nonexistent input
file.
If no infile is specified or infile is a single "-",
base64 reads from standard input; if no outfile is
given, or outfile is a single "-", output is sent to standard
output. The input and output are processed strictly serially;
consequently base64 may be used in pipelines.
BUGS
Little or no error checking is done when decoding, other than
validating that the input consists of a multiple of four
characters in the encoding set. This is inherent in the
design of base64, which assumes transmission integrity is
the responsibility of a higher-level protocol.
SEE ALSO
uudecode(1), uuencode(1)
AUTHOR
John Walker
http://www.fourmilab.ch/
This software is in the public domain. Permission to use, copy,
modify, and distribute this software and its documentation for
any purpose and without fee is hereby granted, without any
conditions or restrictions. This software is provided "as is"
without express or implied warranty.
by John Walker
August 11th, 1997
Download base64.tar.gz (gzipped TAR archive)