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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>cksum</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="cksum"></a> <a name="tag_04_20"></a><!-- cksum --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_04_20_01"></a>NAME</h4><blockquote>cksum - write file checksums and sizes</blockquote><h4><a name="tag_04_20_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>cksum</tt> <b>[</b><i>file</i> <tt>...</tt><b>]</b></code></p></blockquote><h4><a name="tag_04_20_03"></a>DESCRIPTION</h4><blockquote><p>The <i>cksum</i> utility shall calculate and write to standard output a cyclic redundancy check (CRC) for each input file, andalso write to standard output the number of octets in each file. The CRC used is based on the polynomial used for CRC errorchecking in the ISO/IEC 8802-3:1996 standard (Ethernet).</p><p>The encoding for the CRC checksum is defined by the generating polynomial:</p><pre><i>G</i><tt>(</tt><i>x</i><tt>)=</tt><i>x</i><tt><sup><small>32</small></sup>+</tt><i>x</i><tt><sup><small>26</small></sup>+</tt><i>x</i><tt><sup><small>23</small></sup>+</tt><i>x</i><tt><sup><small>22</small></sup>+</tt><i>x</i><tt><sup><small>16</small></sup>+</tt><i>x</i><tt><sup><small>12</small></sup>+</tt><i>x</i><tt><sup><small>11</small></sup>+</tt><i>x</i><tt><sup><small>10</small></sup>+</tt><i>x</i><tt><sup><small>8</small></sup>+</tt><i>x</i><tt><sup><small>7</small></sup>+</tt><i>x</i><tt><sup><small>5</small></sup>+</tt><i>x</i><tt><sup><small>4</small></sup>+</tt><i>x</i><tt><sup><small>2</small></sup>+</tt><i>x</i><tt>+1</tt></pre><p>Mathematically, the CRC value corresponding to a given file shall be defined by the following procedure:</p><ol><li><p>The <i>n</i> bits to be evaluated are considered to be the coefficients of a mod 2 polynomial <i>M</i>( <i>x</i>) of degree<i>n</i>-1. These <i>n</i> bits are the bits from the file, with the most significant bit being the most significant bit of thefirst octet of the file and the last bit being the least significant bit of the last octet, padded with zero bits (if necessary) toachieve an integral number of octets, followed by one or more octets representing the length of the file as a binary value, leastsignificant octet first. The smallest number of octets capable of representing this integer shall be used.</p></li><li><p><i>M</i>( <i>x</i>) is multiplied by <i>x</i><sup><small>32</small></sup> (that is, shifted left 32 bits) and divided by<i>G</i>( <i>x</i>) using mod 2 division, producing a remainder <i>R</i>( <i>x</i>) of degree <= 31.</p></li><li><p>The coefficients of <i>R</i>( <i>x</i>) are considered to be a 32-bit sequence.</p></li><li><p>The bit sequence is complemented and the result is the CRC.</p></li></ol></blockquote><h4><a name="tag_04_20_04"></a>OPTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_20_05"></a>OPERANDS</h4><blockquote><p>The following operand shall be supported:</p><dl compact><dt><i>file</i></dt><dd>A pathname of a file to be checked. If no <i>file</i> operands are specified, the standard input shall be used.</dd></dl></blockquote><h4><a name="tag_04_20_06"></a>STDIN</h4><blockquote><p>The standard input shall be used only if no <i>file</i> operands are specified. See the INPUT FILES section.</p></blockquote><h4><a name="tag_04_20_07"></a>INPUT FILES</h4><blockquote><p>The input files can be any file type.</p></blockquote><h4><a name="tag_04_20_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>The following environment variables shall affect the execution of <i>cksum</i>:</p><dl compact><dt><i>LANG</i></dt><dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> forthe precedence of internationalization variables used to determine the values of locale categories.)</dd><dt><i>LC_ALL</i></dt><dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd><dt><i>LC_CTYPE</i></dt><dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte asopposed to multi-byte characters in arguments).</dd><dt><i>LC_MESSAGES</i></dt><dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standarderror.</dd><dt><i>NLSPATH</i></dt><dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd></dl></blockquote><h4><a name="tag_04_20_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_20_10"></a>STDOUT</h4><blockquote><p>For each file processed successfully, the <i>cksum</i> utility shall write in the following format:</p><pre><tt>"%u %d %s\n", <</tt><i>checksum</i><tt>>, <</tt><i># of octets</i><tt>>, <</tt><i>pathname</i><tt>></tt></pre><p>If no <i>file</i> operand was specified, the pathname and its leading <space> shall be omitted.</p></blockquote><h4><a name="tag_04_20_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_20_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_20_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_20_14"></a>EXIT STATUS</h4><blockquote><p>The following exit values shall be returned:</p><dl compact><dt> 0</dt><dd>All files were processed successfully.</dd><dt>>0</dt><dd>An error occurred.</dd></dl></blockquote><h4><a name="tag_04_20_15"></a>CONSEQUENCES OF ERRORS</h4><blockquote><p>Default.</p></blockquote><hr>⌨️ 快捷键说明
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