Return char[]/string from a function

user1993177 picture user1993177 · Jan 19, 2013 · Viewed 178.9k times · Source

Im fairly new to coding in C and currently im trying to create a function that returns a c string/char array and assigning to a variable.

So far, ive observed that returning a char * is the most common solution. So i tried:

char* createStr() {
    char char1= 'm';
    char char2= 'y';
    char str[3];
    str[0] = char1;
    str[1] = char2;
    str[2] = '\0';
    char* cp = str;
    return cp;
}

My question is how do I use this returned char* and assign the char array it points to, to a char[] variable?

Ive tried (all led to noob-drowning errors):

  1. char* charP = createStr();
  2. char myStr[3] = &createStr();
  3. char* charP = *createStr();

Answer

Rubens picture Rubens · Jan 19, 2013

Notice you're not dynamically allocating the variable, which pretty much means the data inside str, in your function, will be lost by the end of the function.

You should have:

char * createStr() {

    char char1= 'm';
    char char2= 'y';

    char *str = malloc(3);
    str[0] = char1;
    str[1] = char2;
    str[2] = '\0';

    return str;

}

Then, when you call the function, the type of the variable that will receive the data must match that of the function return. So, you should have:

char *returned_str = createStr();

It worths mentioning that the returned value must be freed to prevent memory leaks.

char *returned_str = createStr();

//doSomething
...

free(returned_str);