#include <stdlib.h>
    void *bsearch(const void *key, const void *base, size_t nitems, size_t size, int (*compare)(const void *, const void *));

key - The element that is searched for
base - pointer to the first element of the array to be searched
nitems - number of elements in the array
size - size of a single element
compare - comparison function to compare two elements together.

pointer to an entry in the array that matches the search key.
If key not found, NULL pointer returned.

#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 
#include <stdlib.h>
#include <string.h>
 
int main ( void )
{
  char my_key[10] = "bsearch";
  int  my_elementCount = 4;
  int  my_size = 20;
  char my_strings[][30] = {"c", "example", "bsearch", "coderefer" , "someusefulinformation"};
 
  /* strcmp is the compare function for this bsearch */
  char *return_value = (char*) bsearch(my_key, my_strings, my_elementCount, my_size, (int(*)(const void*, const void*))strcmp);
 
  if (return_value) {
    printf("Found \"%s\" in the my_strings array.\n", return_value);
  }
  else {
    printf("Did not found \"%s\" in the my_strings array.\n", my_key);
  }
 
  return 0;
}

  user@host:~$ ./bsearch 
  Found "bsearch" in the my_strings array