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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>lsearch</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="lsearch"></a> <a name="tag_03_353"></a><!-- lsearch --> <!--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_03_353_01"></a>NAME</h4><blockquote>lsearch, lfind - linear search and update</blockquote><h4><a name="tag_03_353_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/search.h.html">search.h</a>><br><br> void *lsearch(const void *</tt><i>key</i><tt>, void *</tt><i>base</i><tt>, size_t *</tt><i>nelp</i><tt>, size_t</tt><i>width</i><tt>,<br> int (*</tt><i>compar</i><tt>)(const void *, const void *));<br> void *lfind(const void *</tt><i>key</i><tt>, const void *</tt><i>base</i><tt>, size_t *</tt><i>nelp</i><tt>,<br> size_t width, int (*</tt><i>compar</i><tt>)(const void *, const void *)); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_353_03"></a>DESCRIPTION</h4><blockquote><p>The <i>lsearch</i>() function shall linearly search the table and return a pointer into the table for the matching entry. If theentry does not occur, it shall be added at the end of the table. The <i>key</i> argument points to the entry to be sought in thetable. The <i>base</i> argument points to the first element in the table. The <i>width</i> argument is the size of an element inbytes. The <i>nelp</i> argument points to an integer containing the current number of elements in the table. The integer to which<i>nelp</i> points shall be incremented if the entry is added to the table. The <i>compar</i> argument points to a comparisonfunction which the application shall supply (for example, <a href="../functions/strcmp.html"><i>strcmp</i>()</a>). It is calledwith two arguments that point to the elements being compared. The application shall ensure that the function returns 0 if theelements are equal, and non-zero otherwise.</p><p>The <i>lfind</i>() function shall be equivalent to <i>lsearch</i>(), except that if the entry is not found, it is not added tothe table. Instead, a null pointer is returned.</p></blockquote><h4><a name="tag_03_353_04"></a>RETURN VALUE</h4><blockquote><p>If the searched for entry is found, both <i>lsearch</i>() and <i>lfind</i>() shall return a pointer to it. Otherwise,<i>lfind</i>() shall return a null pointer and <i>lsearch</i>() shall return a pointer to the newly added element.</p><p>Both functions shall return a null pointer in case of error.</p></blockquote><h4><a name="tag_03_353_05"></a>ERRORS</h4><blockquote><p>No errors are defined.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_353_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_353_06_01"></a>Storing Strings in a Table</h5><p>This fragment reads in less than or equal to TABSIZE strings of length less than or equal to ELSIZE and stores them in a table,eliminating duplicates.</p><pre><tt>#include <stdio.h>#include <string.h>#include <search.h><br>#define TABSIZE 50#define ELSIZE 120<br>... char line[ELSIZE], tab[TABSIZE][ELSIZE]; size_t nel = 0; ... while (fgets(line, ELSIZE, stdin) != NULL && nel < TABSIZE) (void) lsearch(line, tab, &nel, ELSIZE, (int (*)(const void *, const void *)) strcmp); ...</tt></pre><h5><a name="tag_03_353_06_02"></a>Finding a Matching Entry</h5><p>The following example finds any line that reads <tt>"This is a test."</tt> .</p><pre><tt>#include <search.h>#include <string.h>...char line[ELSIZE], tab[TABSIZE][ELSIZE];size_t nel = 0;char *findline;void *entry;<br>findline = "This is a test.\n";<br>entry = lfind(findline, tab, &nel, ELSIZE, ( int (*)(const void *, const void *)) strcmp);</tt></pre></blockquote><h4><a name="tag_03_353_07"></a>APPLICATION USAGE</h4><blockquote><p>The comparison function need not compare every byte, so arbitrary data may be contained in the elements in addition to thevalues being compared.</p><p>Undefined results can occur if there is not enough room in the table to add a new item.</p></blockquote><h4><a name="tag_03_353_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_353_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_353_10"></a>SEE ALSO</h4><blockquote><p><a href="hcreate.html"><i>hcreate</i>()</a> , <a href="tsearch.html"><i>tsearch</i>()</a> , the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/search.h.html"><i><search.h></i></a></p></blockquote><h4><a name="tag_03_353_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_353_12"></a>Issue 6</h4><blockquote><p>The DESCRIPTION is updated to avoid use of the term "must" for application requirements.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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