strtok wont accept: char *str

Question

strtok wont work correctly when using char *str as the first parameter (not the delimiters string).

Does it have something to do with the area that allocates strings

Answer 1

In the first case, you pass a string literal to strtok(). As strtok() modifies this string, and as string literals cannot legally be modified, you end up with undefined behaviour. In the second case, the compiler copies the string into the array. Array contents can be modified, so this code is OK.