Consider the following snippet that uses strtok to split the string madddy.

char* str = (char*) malloc(sizeof("Madddy"));
strcpy(str,"Madddy");

char* tmp = strtok(str,"d");
std::cout<<tmp;

do
{
    std::cout<<tmp;
    tmp=strtok(NULL, "dddy");
}while(tmp!=NULL);

It works fine, the output is Ma. But by modifying the strtok to the following,

tmp=strtok(NULL, "ay");

The output becomes Madd. So how does strtok exactly work? I have this question because I expected strtok to take each and every character that is in the delimiter string to be taken as a delimiter. But in certain cases it is doing that way but in few cases, it is giving unexpected results. Could anyone help me understand this?