Using Rand() populate Multidimensional Array

Question

I am completing an exercise in which I want to create an array and populate it with random and meaningless IP addresses.

It is supposed to be a 2 dimensional array[5][4]. It is 5 addresses, each consisting of 4 parts( i.e. {192, 168, 0 ,1}. My trouble comes from using the rand() function to populate only one dimension of the array. I cannot figure out how to do it in a way that:

1. the compiler accepts,
2. won't crash the program, and
3. won't produce an entirely random result.

Although my main issue comes from the for loop for (int o = 0; o < octets; o++) below , feel free to comment on any of my code, best practices, etc.

#include <stdio.h>
#include <stdlib.h>
int main() {
 const int addresses = 5, octets = 4;
 int ips[addresses][octets];
 for (int a = 0; a < addresses; a++) {
 for (int o = 0; o < octets; o++) {
 ips[octets] = rand() % 255;
 }
 }
 for (int i = 0; i < addresses; i++) {
 for (int j = 0; j < octets; j++) {
 printf("%d ", ips[i][j]);
 }
 putchar('\n');
 }
 return 0;
}

The compiler error for this code is... :

ipAddressArray.c: In function 'main':
ipAddressArray.c:18:18: error: incompatible types when assigning to type 'int[(s
izetype)octets]' from type 'int' ps[octets] = rand()%255;

• juanchopanza: You need to think about what ips[octets] is.

Answer 1

Rewrite this loop like

for (int a = 0; a < addresses; a++) {
 for (int o = 0; o < octets; o++) {
 ips[a][o] = rand() % 255;
 }
}