Passing pointer to pointer to pointer as a function parameter

Question

Could anyone explain me how to pass 2D array of strings to a function using another pointer ? I want to pass array to a function FILL using pointer. In that function I want to copy a string to an array.

void FILL(char **array) {

    char buffer[20] = "Hi my name is John."

    array = (char**) malloc ( 1 * sizeof(char*));
    for ( i = 0; i < 1; i++ ) {
        array[i] = (char*) malloc ( 20 * sizeof(char*));
        strcpy(array[i],buffer);
    }
}

int main() 
{

 char **array = NULL;

 FILL(array);

 return 0;
}

You have to become a three-star programmer and learn about how to emulate pass by reference in c. — Some programmer dude
– Some programmer dude, Commented Dec 24, 2015 at 13:10

fuz · Accepted Answer · 2015-12-24 13:13:17Z

1

Just use a triple pointer to char (and enjoy being called a three-star programmer):

void FILL(char ***array);

int main()
{
    char **array;

    FILL(&array);

    return 0;
}

Alternatively, consider returning the allocated memory segment in FILL instead of passing a pointer:

char **FILL() {
    char **array = ...;

    ...

    return array;
}

int main()
{
    char **array = FILL();
    ...
}

edited Dec 24, 2015 at 13:13

answered Dec 24, 2015 at 13:11

fuz

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3 Comments

glery Over a year ago

And how to change the inside of the function ? *array?

glery Over a year ago

Any advantages over using another pointer in your second example?

fuz Over a year ago

@glery Both approaches have their use cases although you could always emulate the second through the first.

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