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Add a sample program that shows how a custom comparison function and

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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
This commit is contained in:
Giorgos Keramidas 2013-02-19 23:57:39 +00:00
parent e9e9223546
commit 8ce3e01e09
1 changed files with 47 additions and 1 deletions
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48
lib/libc/stdlib/qsort.3
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@ -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