Example

#include <stdio.h>
#include <stdlib.h>

#define SSIZE 30

extern int compare();  /* prototype for comparison function */

int array[SSIZE] = {30, 1, 29, 2, 28, 3, 27, 4, 26, 5,
                    24, 6, 23, 7, 22, 8, 21, 9, 20, 10,
                    19, 11, 18, 12, 17, 13, 16, 14, 15, 25};

 /*  This program takes an unsorted array, sorts it using qsort, */
 /*  and then calls bsearch for each element in the array,       */
 /*  making sure that bsearch returns the correct element.       */

main()
{
    int i;
    int failure = FALSE;
    int *rkey;

    qsort(array, SSIZE, sizeof (array[0]), &compare);

    /* search for each element */
    for (i = 0; i < SSIZE - 1; i++) {
        /* search array element i */
        rkey = bsearch((array + i), array, SSIZE,
                        sizeof(array[0]), &compare);
        /* check for successful search */
        if (&array[i] != rkey) {
            printf("Not in array, array element %d\n", i);
            failure = TRUE;
            break;
        }
    }
    if (!failure)
        printf("All elements successfully found!\n");
}

 /*  Simple comparison routine.  */
 /*                              */
 /*  Returns:  = 0 if a == b     */
 /*            < 0 if a < b      */
 /*            > 0 if a > b      */

int compare(int *a, int *b)
{
    return (*a - *b);
}

     This example program outputs the following:

       All elements successfully found!