wcschr

#include <wchar.h>
#include <stdio.h>
#include <locale.h>
 
int main(void)
{
    wchar_t arr[] = L"招き猫 кошка";
    wchar_t *cat = wcschr(arr, L'猫');
    wchar_t *dog = wcschr(arr, L'犬');
 
    setlocale(LC_ALL, "en_US.utf8");
    if(cat)
        printf("The character 猫 found at position %td\n", cat-arr);
    else
        puts("The character 猫 not found");
 
    if(dog)
        printf("The character 犬 found at position %td\n", dog-arr);
    else
        puts("The character 犬 not found");
}