Performs a binary search of a sorted array.
void *bsearch( const void *key, const void *base, size_t num, size_t width, int ( __cdecl *compare ) ( const void *elem1, const void *elem2 ) );
| Routine | Required Header | Compatibility |
| bsearch | <stdlib.h> and <search.h> | ANSI, Win 95, Win NT |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
| LIBC.LIB | Single thread static library, retail version |
| LIBCMT.LIB | Multithread static library, retail version |
| MSVCRT.LIB | Import library for MSVCRT.DLL, retail version |
Return Value
bsearch returns a pointer to an occurrence of key in the array pointed to by base. If key is not found, the function returns NULL. If the array is not in ascending sort order or contains duplicate records with identical keys, the result is unpredictable.
Parameters
key
Object to search for
base
Pointer to base of search data
num
Number of elements
width
Width of elements
compare
Function that compares two elements: elem1 and elem2
elem1
Pointer to the key for the search
elem2
Pointer to the array element to be compared with the key
Remarks
The bsearch function performs a binary search of a sorted array of num elements, each of width bytes in size. The base value is a pointer to the base of the array to be searched, and key is the value being sought. The compare parameter is a pointer to a user-supplied routine that compares two array elements and returns a value specifying their relationship. bsearch calls the compare routine one or more times during the search, passing pointers to two array elements on each call. The compare routine compares the elements, then returns one of the following values:
| Value Returned by compare Routine | Description |
| < 0 | elem1 less than elem2 |
| 0 | elem1 equal to elem2 |
| > 0 | elem1 greater than elem2 |
Example
/* BSEARCH.C: This program reads the command-line
* parameters, sorting them with qsort, and then
* uses bsearch to find the word "cat."
*/
#include <search.h>
#include <string.h>
#include <stdio.h>
int compare( char **arg1, char **arg2 ); /* Declare a function for compare */
void main( int argc, char **argv )
{
char **result;
char *key = "cat";
int i;
/* Sort using Quicksort algorithm: */
qsort( (void *)argv, (size_t)argc, sizeof( char * ), (int (*)(const
void*, const void*))compare );
for( i = 0; i < argc; ++i ) /* Output sorted list */
printf( "%s ", argv[i] );
/* Find the word "cat" using a binary search algorithm: */
result = (char **)bsearch( (char *) &key, (char *)argv, argc,
sizeof( char * ), (int (*)(const void*, const void*))compare );
if( result )
printf( "\n%s found at %Fp\n", *result, result );
else
printf( "\nCat not found!\n" );
}
int compare( char **arg1, char **arg2 )
{
/* Compare all of both strings: */
return _strcmpi( *arg1, *arg2 );
}
Output
[C:\work]bsearch dog pig horse cat human rat cow goat
bsearch cat cow dog goat horse human pig rat
cat found at 002D0008