bsearch() - binary search of a sorted table
#include <stdlib.h>
void * bsearch (const void *key, const void *base, size_t nmemb,
size_t size, int (*compar) (const void *, const void *))
The bsearch(3) function searches an array of nmemb objects, for a member that matches the object pointed to by key. Base points to the initial member of the array, and the size of each member of the array is specified by size.
The contents of the array should be in ascending sorted order according to the comparison function referenced by compar. (See qsort(3)). The compar routine is expected to have two arguments which point to the key object and to an array member, in that order, and should return an integer less than, equal to, or greater than zero if the key object is found, respectively, to be less than, to match, or be greater than the array member.
The bsearch(3) function returns a pointer to a matching member of the array, or NULL if no match is found. If two members compare as equal, which member is matched is unspecified.
qsort(3)