Getting Null values when using strtok [C]

Question

I am working on a project which involves using strtok and for some reason I am getting null values instead of the actual values (which should be "Two" and "Three"). Here is my code:

int main(){
    int h,z;

    char text[100] = "One Two Three";

    for(h = 0; h < 4; h ++){

        char *first = strtok(text, " ");
        printf("%s\n",first);

        for(z = 0;  z < 3; z++){
            char *second = strtok(NULL,  " ");
            printf("%s\n",second);


        }
    }
    return 0;
}

The output I am getting is:

One
Two
Three
One
(null)
(null)
One
(null)
(null)
One
(null)
(null)

What can I do in order to get the right value Two and Three instead of null?

Answer 1

Note that your code actually re-tokenizes the string text 4 times, as you have nested loops. Note also that z < 3 is one off and should be z < 2:

int main(){
    int h,z;

    char text[100] = "One Two Three";

    for(h = 0; h < 4; h ++){

        char *first = strtok(text, " ");
        printf("%s\n",first);

        for(z = 0;  z < 2; z++){
            char *second = strtok(NULL,  " ");
            printf("%s\n",second);


        }
    }
    return 0;
}

But strtok introduces '\0'-characters each time a token is found. Hence, after the first run of the for(h...)-loop, text will be "One", and for any subsequent loops only one token can be found; tokens #2 and #3 do not exist in "One".

To re-tokenize (for whatever reason), you'll have to re-initialize text:

int main(){
    int h,z;

    char text[100];

    for(h = 0; h < 4; h ++){

        strcpy(text,"One Two Three");

        char *first = strtok(text, " ");
        printf("%s\n",first);

        for(z = 0;  z < 2; z++){
            char *second = strtok(NULL,  " ");
            printf("%s\n",second);
        }
    }
    return 0;
}