Appending to string as input argument

Question

I am having trouble generating a string inside a C routine.

Goal

• Have function generate a custom string and return the value
• e.g. 'void getName( char ** name )'

Attempt

int main(void) {
    char *name;
    getName(&name);
}

void getName(char **name) {
    *name = "#";                    // Load with prefix
    //?strcpy(*name[1], "123");     // Goal: "#123"
}

How can I have getName() generate #123 as shown here?

Answer 1

1st problem: use malloc to allocate memory.

char *name = malloc(sizeof("#123")+1);

Even if you will run it after allocating memory, it will give runtime error; as you are doing:

*name = "#";

The problem is first you allocate space for 5 chars and point your pointer to the beginning of that memory. Then in the second line you point your pointer to a string literal causing a memory leak.

The pointer no longer points to the allocated memory.

You will like to do this:

int main(void) {
    char *name = malloc(sizeof("#123")+1);
    getName(&name);
    printf("%s", name);
    free(name);
    name = NULL;
}

void getName(char **name) {
   strcpy((*name), "#");
   strcat(*name,"123");
}