al_ustr_find_str - Allegro 5 API

       Find the first occurrence of string needle in haystack, beginning from byte offset start_pos (inclusive).
       Return the byte offset of the occurrence if it is found, otherwise return -1.

       al_ustr_find_str - Allegro 5 API

al_ustr_find_cstr(3alleg5), al_ustr_rfind_str(3alleg5), al_ustr_find_replace(3alleg5)

Allegro reference manual                                                               al_ustr_find_str(3alleg5)

              #include <allegro5/allegro.h>

              int al_ustr_find_str(const ALLEGRO_USTR *haystack, int start_pos,
                 const ALLEGRO_USTR *needle)