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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html version="-//W3C//DTD HTML 3.2 Final//EN"><head><title>Base64: Encode and Decode Base64 Files</title><style type="text/css"> DIV.bodycopy { margin-left: 15%; margin-right: 10% }</style><meta name="keywords" content="Base64, encode, decode, utility, RFC 1341, MIME"><meta name="description" content="Base64: Encode and Decode Base64 Files"><meta name="author" content="John Walker"><meta name="robots" content="index"><meta name="robots" content="nofollow"></head><body bgcolor="#FFFFFF"><center><h1><img src="b64.gif" width=512 height=144 alt="Base64: Encode and Decode Base64 Files"></h1></center><hr><div class="bodycopy"><p>This page describes, in Unix manual page style,a program<a href="#Download">available for downloading</a> from this sitewhich encodes binary files in the "Base64" format used byMIME-encoded documents such as electronic mail messages withembedded images and audio files.<h3>NAME</h3><blockquote> <b>base64</b> - encode and decode base64 files</blockquote><h3>SYNOPSIS</h3><blockquote> <tt>base64</tt> [ <tt>-d</tt> / <tt>-e</tt> ] [ <em>options</em> ] [ <em>infile</em> ] [ <em>outfile</em> ]</blockquote><h3>DESCRIPTION</h3>The MIME (Multipurpose Internet Mail Extensions) specification(<a href="rfc1341.html">RFC 1341</a> and successors)defines a mechanism for encoding arbitrary binaryinformation for transmission by electronic mail. Triplets of 8-bitoctets are encoded as groups of four characters, each representing 6bits of the source 24 bits. Only characters present in all variantsof ASCII and EBCDIC are used, avoiding incompatibilities in otherforms of encoding such as <b>uuencode</b>/<b>uudecode</b>.<p><b>base64</b>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 automatedmail processing system.<h3>OPTIONS</h3><dl compact><dt><b>--copyright</b><dd>Print copyright information.<p><dt><b>-d</b>, <b>--decode</b><dd>Decodes the input, previously created by<b>base64</b>,to recover the original input file. <p><dt><b>-e</b>, <b>--encode</b><dd>Encodes the input into an output text file containingits base64 encoding. <p><dt><b>-n</b>, <b>--noerrcheck</b> <dd>Suppress error checking when decoding. By default, upon encounteringa non white space character which does not belong to the base64set, or discovering the input file is incorrectly padded to amultiple of four characters, <b>base64</b> issues an errormessage and terminatesprocessing with exit status 1. The<b>-n</b>option suppresses even this rudimentary error checking; invalidcharacters are silently ignored and the output truncated to thelast three valid octets if the input is incorrectly padded. <p><dt><b>-u</b>, <b>--help</b> <dd> Print how to call information and a summary of options.<p><dt><b>--version</b> <dd>Print program version information.</dl><h3>EXIT STATUS</h3><b>base64</b>returns status 0 if processing was completed without errors, 1 if anI/O error occurred or errors were detected in decoding a file whichindicate it is incorrect or incomplete, and 2 if processingcould not be performed at all due, for example, to a nonexistent inputfile.<h3><a name="files">FILES</a></h3>If no <i>infile</i> is specified or <i>infile</i> is a single "-",<b>base64</b> reads from standard input; if no <i>outfile</i> isgiven, or <i>outfile</i> is a single "-", output is sent to standardoutput. The input and output are processed strictly serially;consequently <b>base64</b> may be used in pipelines.<h3>BUGS</h3>Little or no error checking is done when decoding, other thanvalidating that the input consists of a multiple of fourcharacters in the encoding set. This is inherent in thedesign of base64, which assumes transmission integrity isthe responsibility of a higher-level protocol.<h3>SEE ALSO</h3> <b>uudecode</b>(1), <b>uuencode</b>(1), <a href="rfc1341.html">RFC 1341</a><h2><a name="Download" href="base64-1.3.tar.gz"><img src="/images/icons/file.gif" alt="" align=middle width=40 height=40></a> <a href="base64-1.3.tar.gz">Download base64-1.3.tar.gz</a> (Gzipped TAR archive)</h2>The archive contains source code for the utility, a Makefilefor Unix systems, and a ready-to-run executable for 32-bitWindows platforms. Windows users may also download<a href="base64.zip"><b><tt>base64.zip</tt></b></a>, aZIPped archive containing the Windows executable.<h3>AUTHOR</h3><address> <a href="/">John Walker</a><br> <a href="/">http://www.fourmilab.ch/</a></address><p>Christian Ferrari contributed code which permits the <b>base64</b>utility to work on EBCDIC based systems such asUNIX Services for OS/390 2.7 (ESA/390).<p><blockquote> 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.</blockquote></div><p><hr><p><address>by <a href="/">John Walker</a><br>February 20th, 2001<br>Version 1.3<br>The latest version of this program is available from:<a href="http://www.fourmilab.ch/webtools/base64/">http://www.fourmilab.ch/webtools/base64/</a>.</address></body></html>⌨️ 快捷键说明
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