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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /><title>MD5: Command Line Message Digest Utility</title><meta name="author" content="John Walker" /><meta name="description" content="MD5: Command Line Message Digest Utility" /><meta name="keywords" content="md5, message, digest, signature, command, line, utility" /><meta name="robots" content="index" /><link rel="stylesheet" href="/documents/styles/standard_screen.css" type="text/css" /><style type="text/css"> dd { text-align: justify; } dt { margin-top: 1ex; }</style></head><body class="standard"><center><h1><img src="md5.png" width="208" height="109" alt="MD5" /></h1><h2>Command Line Message Digest Utility</h2></center><hr /><p class="j">This page describes <b>md5</b>, a command line utility usable oneither Unix or MS-DOS/Windows, which generates and verifiesmessage digests (digital signatures) using the MD5 algorithm.This program can be useful when developing shell scripts or Perlprograms for software installation, file comparison, anddetection of file corruption and tampering.</p><h3>NAME</h3> <b>md5</b> - generate / check MD5 message digest<h3>SYNOPSIS</h3> <b>md5</b> [ <b>-c</b><i>signature</i> ] [ <b>-l</b> ] [ <b>-n</b> ] [ <b>-u</b> ] [ <b>-v</b> ] [ <b>-d</b><i>input_text</i> | <em>infile</em>… ]<h3>DESCRIPTION</h3><p class="j">A <em>message digest</em> is a compact digital signature for anarbitrarily long stream of binary data. An ideal message digestalgorithm would never generate the same signature for twodifferent sets of input, but achieving such theoreticalperfection would require a message digest as long as the inputfile. Practical message digest algorithms compromise in favourof a digital signature of modest size created with an algorithmdesigned to make preparation of input text with a givensignature computationally infeasible. Message digest algorithmshave much in common with techniques used in encryption, but to adifferent end; verification that data have not been alteredsince the signature was published.</p><p class="j">Many older programs requiring digital signatures employed 16 or32 bit <em>cyclical redundancy codes</em> (CRC) originallydeveloped to verify correct transmission in data communicationprotocols, but these short codes, while adequate to detect thekind of transmission errors for which they were intended, areinsufficiently secure for applications such as electroniccommerce and verification of security related softwaredistributions.</p><p class="j">The most commonly used present-day message digest algorithm isthe 128 bit MD5 algorithm, developed by Ron Rivest of the<a href="http://web.mit.edu/" target="_blank">MIT</a><a href="http://www.lcs.mit.edu/" target="_blank">Laboratory for Computer Science</a> and<a href="http://www.rsa.com/" target="_blank">RSA Data Security,Inc.</a> The algorithm, with a reference implementation, waspublished as Internet <a href="rfc1321.html">RFC 1321</a> in April 1992, and wasplaced into the public domain at that time. Messagedigest algorithms such as MD5 are not deemed“encryption technology” and are not subject to theexport controls some governments impose onother data security products. (Obviously, theresponsibility for obeying the laws in the jurisdictionin which you reside is entirely your own, but manycommon Web and Mail utilities use MD5, and I am unawareof any restrictions on their distribution and use.)</p><p class="j">The MD5 algorithm has been implemented in numerouscomputer languages including C,<a href="http://www.perl.org/" target="_blank">Perl</a>, and<a href="http://java.sun.com/" target="_blank">Java</a>; if you'rewriting a program in such a language, track down a suitablesubroutine and incorporate it into your program. Theprogram described on this page is a <em>command line</em>implementation of MD5, intended for use in shell scriptsand Perl programs (it is much faster than computingan MD5 signature directly in Perl). This <b>md5</b>program was originally developed as part of a suite of toolsintended to monitor large collections of files (for example,the contents of a Web site) to detect corruption offiles and inadvertent (or perhaps malicious) changes. Thattask is now best accomplished with more comprehensivepackages such as<a href="http://www.tripwire.com/" target="_blank">Tripwire</a>,but the command line <b>md5</b> component continues to prove usefulfor verifying correct delivery and installation of software packages,comparing the contents of two different systems, and checking forchanges in specific files.</p><h3>OPTIONS</h3><dl><dt><b>-c</b><i>signature</i></dt> <dd>Computes the signature of the specified <em>infile</em> or the string supplied by the <b>-d</b> option and compares it against the specified <i>signature</i>. If the two signatures match, the exit status will be zero, otherwise the exit status will be 1. No signature is written; only the exit status is set. The signature to be checked must be specified as 32 hexadecimal digits.</dd><dt><b>-d</b><i>input_text</i></dt> <dd>A signature is computed for the given <i>input_text</i> (which must be quoted if it contains white space characters) instead of input from <i>infile</i> or standard input. If input is specified with the <b>-d</b> option, no <i>infile</i> should be specified.</dd> <dt><b>-l</b></dt> <dd>Use lower case letters for hexadecimal digits “a” through “f”. By default, upper case letters are used. Note that the <i>signature</i> argument to the <b>-c</b> option may use upper or lower case hexadecimal digits (or a mix) regardless of the setting of this option.</dd><dt><b>-n</b></dt> <dd>Suppress printing the file name (or “<tt>-</tt>” for standard input) after the hexadecimal signature.</dd><dt><b>-o</b><i>fname</i></dt> <dd>Write output to <i>fname</i>. If <i>fname</i> is “<tt>-</tt>”, output is written to standard output, which is the default is no <b>-o</b> option is specified.</dd><dt><b>-u</b></dt> <dd>Print how-to-call information.</dd><dt><b>-v</b></dt> <dd>Print version information.</dd></dl><h3>FILES</h3><p class="j"> If no <em>infile</em> or <b>-d</b> option is specified or <em>infile</em> is a single “<tt>-</tt>”, <b>md5</b> reads from standard input. A single “<tt>-</tt>” on the command line causes all subsequent arguments to be treated as file names even if they begin with “<tt>-</tt>”. If no <b>-o</b> option is specified or the <em>fname</em> is a single “<tt>-</tt>”, output is sent to standard output. Input and output are processed strictly serially; consequently <b>md5</b> may be used in pipelines.</p><h3>BUGS</h3><p class="j">The mechanism used to set standard input to binary mode may bespecific to Microsoft C; if you rebuild the DOS/Windows versionof the program from source using another compiler, be sure to verifybinary files work properly when read via redirection or a pipe.</p><p class="j">This program has not been tested on a machine on which <tt>int</tt>and/or <tt>long</tt> are longer than 32 bits.</p><h2><img src="/images/icons/file.png" alt="" align="middle" width="40" height="40" /> Download <a href="md5.zip">md5.zip</a> (Zipped) or <a href="md5.tar.gz">md5.tar.gz</a> (tar/gzip)</h2><p class="j"> The program is provided as either <a href="md5.zip">md5.zip</a>, a <a href="http://www.info-zip.org/" target="_blank">Zipped</a> archive, or <a href="md5.tar.gz">md5.tar.gz</a>, a <tt>gzip</tt>ped <tt>tar</tt> archive. The two archive formats have identical contents; both include a ready-to-run Win32 command-line executable program, <code>md5.exe</code> (compiled using Microsoft Visual C++ .NET), and source code along with a <code>Makefile</code> to build the program under Unix.</p><h3>SEE ALSO</h3> <b>sum</b>(1)<h3>EXIT STATUS</h3><p class="j"> <b>md5</b> returns status 0 if processing was completed without errors, 1 if the <b>-c</b> option was specified and the given signature does not match that of the input, and 2 if processing could not be performed at all due, for example, to a nonexistent input file.</p><h3>COPYING</h3><blockquote><p class="j"> 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.</p></blockquote><h3>ACKNOWLEDGEMENTS</h3><p class="j">The MD5 algorithm was developed by Ron Rivest. The publicdomain C language implementation used in this program waswritten by Colin Plumb in 1993.</p><h3><a href="/">Fourmilab home page</a></h3><hr /><address><a href="/">by John Walker</a><br />January 14th, 2008</address></body></html>⌨️ 快捷键说明
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