Date: Tue, 19 Feb 2013 23:57:40 +0000 (UTC) From: Giorgos Keramidas <keramida@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r247014 - head/lib/libc/stdlib Message-ID: <201302192357.r1JNveLq039940@svn.freebsd.org>
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Author: keramida (doc committer) Date: Tue Feb 19 23:57:39 2013 New Revision: 247014 URL: http://svnweb.freebsd.org/changeset/base/247014 Log: Add a sample program that shows how a custom comparison function and qsort(3) can work together to sort an array of integers. PR: docs/176197 Submitted by: Fernando, fapesteguia at opensistemas.com Approved by: gjb (mentor) MFC after: 1 week Modified: head/lib/libc/stdlib/qsort.3 Modified: head/lib/libc/stdlib/qsort.3 ============================================================================== --- head/lib/libc/stdlib/qsort.3 Tue Feb 19 23:46:51 2013 (r247013) +++ head/lib/libc/stdlib/qsort.3 Tue Feb 19 23:57:39 2013 (r247014) @@ -32,7 +32,7 @@ .\" @(#)qsort.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD$ .\" -.Dd September 30, 2003 +.Dd February 20, 2013 .Dt QSORT 3 .Os .Sh NAME @@ -211,6 +211,52 @@ Previous versions of did not permit the comparison routine itself to call .Fn qsort 3 . This is no longer true. +.Sh EXAMPLES +A sample program that sorts an array of +.Vt int +values in place using +.Fn qsort , +and then prints the sorted array to standard output is: +.Bd -literal +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +/* + * Custom comparison function that can compare 'int' values through pointers + * passed by qsort(3). + */ +static int +int_compare(const void *p1, const void *p2) +{ + int *left = (int *)p1; + int *right = (int *)p2; + + if (*left < *right) + return (-1); + else if (*left > *right) + return (1); + else + return (0); +} + +/* + * Sort an array of 'int' values and print it to standard output. + */ +int +main(void) +{ + int int_array[] = { 4, 5, 9, 3, 0, 1, 7, 2, 8, 6 }; + const int array_size = sizeof(int_array) / sizeof(int_array[0]); + int k; + + qsort(&int_array, array_size, sizeof(int), int_compare); + for (k = 0; k < array_size; k++) + printf(" %d", int_array[k]); + printf("\\n"); + exit(EXIT_SUCCESS); +} +.Ed .Sh ERRORS The .Fn heapsort
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