Passing array from main function to other functions in C

Question

I have a dynamic array of strings initialized in the main function, but I'm not sure how to properly use pointers and send my array to function. In the function_w I want to work with the array and then send it back to main function, and later to use in other functions. This is my code:

char function_w(char **array,FILE **fr)
{
int i = 0, strcount = 0;
int buf_length = 50; 
char buf [buf_length],p = NULL;
fseek(*fr, 0, SEEK_SET);

 while (fgets(buf, buf_length, *fr) != NULL)
 {
    array = (char **)realloc(array, (strcount + 1) * sizeof(char *));
    array[strcount++] = strdup(buf);
 }
return p;
}

int main(void)
{   
    char **array = NULL;
    FILE*fr = NULL; //file is opened in other function, before calling w
...
    if (fr != NULL) **array = function_w(array,&fr);
    else printf("Error");
return 0;
}

Every time I use function_w there's no output. Can you help me?

Answer 1

• To have functions modify what are passed, pass pointers to what should be modified. What should be modified is char** in this case, so a pointer to that is char*** .
• The caller of function_w will want the information strcount , so you should return that.
• You won't need a pointer to FILE* because you don't modify that.

Applying these, your program should be like this:

int function_w(char ***array,FILE *fr)
{
    int i = 0, strcount = 0;
    int buf_length = 50; 
    char buf [buf_length],p = NULL;
    fseek(fr, 0, SEEK_SET);

    while (fgets(buf, buf_length, fr) != NULL)
    {
        *array = realloc(*array, (strcount + 1) * sizeof(char *));
        (*array)[strcount++] = strdup(buf);
    }
    return strcount;
}

int main(void)
{   
    char **array = NULL;
    FILE*fr = NULL; //file is opened in other function, before calling w
    int strcount;
...
    if (fr != NULL) strcount = function_w(&array,fr);
    else printf("Error");
    return 0;
}