| Item | Value |
| Header file | stdlib.h |
| Declaration | void *bsearch(const void *key, const void *buf, size_t num, size_t size, int (*compare)(const void *, const void *)); |
| Function | performs a binary search on the sorted array *buf |
| Return | returns a pointer to the first member that matches *key. If the array does not contain the key, a null pointer is returned. |
| Parameter | The array must be sorted in ascending order. The number of elements in the array is specified by num, and the size (in bytes) of each element is described by size. |
The function pointed to by compare is used to compare an element of the array with the key.
The form of the compare function must be as follows:
int func_name(const void *arg1, const void *arg2);
It must return values as described in the following table:
| Comparison | Value Returned |
| arg1 < arg2 | < 0 |
| arg1 == arg2 | 0 |
| arg1 > arg2 | > 0 |
#include <stdlib.h>
#include <ctype.h>
#include <stdio.h>
char *alpha = "abcdefghijklmnopqrstuvwxyz";
int comp(const void *ch, const void *s);
int main(void)
{
char ch;
char *p;
printf("Enter a character: ");
ch = getchar();
ch = tolower(ch);
p = (char *) bsearch(&ch, alpha, 26, 1, comp);
if(p) printf(" %c is in alphabet\n", *p);
else printf("is not in alphabet\n");
return 0;
}
/* Compare two characters. */
int comp(const void *ch, const void *s)
{
return *(char *)ch - *(char *)s;
}
| 23.8.bsearch | ||||
| 23.8.1. | bsearch | |||