bsearch - binary search of a sorted array.
void *bsearch(const void *key, const void *base, size_t nmemb,
size_t size, int (*compar)(const void *, const void *));
The bsearch() function searches an array of nmemb objects,
the initial member of which is pointed to by base, for a
member that matches the object pointed to by key. 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. The compar routine is expected to have two argu
ments which point to the key object and to an array mem
ber, 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() function returns a pointer to a matching
member of the array, or NULL if no match is found. If
there are multiple elements that match the key, the ele
ment returned is unspecified.
SVID 3, BSD 4.3, ISO 9899