random or rand function prints the same value, even in different machines

Question

I want to print a random number in the range 1 to 6. I have the following code.

printf(\"The random value is %d \\n\",random(6));

It is pri

Answer 1

You shoud have srand() before rand() to generate new numbers each time. This code will show how do that:

# include <time.h>
# include <stdlib.h>
# inlcude <stdio.h>

int main()
{
    srand(time(0));
    printf("The random value is %d\n", 1 + rand() % 6);
    return 0;
}

Answer 2

First of all, random() does not take any arguments.

Secondly, from the fine manual:

Like rand(), random() shall produce by default a sequence of numbers that can be duplicated by calling srandom() with 1 as the seed.

So, unless you explicitly specify a seed by calling srandom(), random() will produce the same sequence of values every time.

Thirdly, random() returns a long so you should be using %ld in your printf() call.

Fourthly, learn about your compiler's warning flags, turn them all on, and pay attention to their output. You can turn off some of the warning flags once you understand why it is safe to do so.

Answer 3

The srand() function sets its argument as the seed for a new sequence of pseudo-random integers to be returned by rand(). These sequences are repeatable by calling srand() with the same seed value.

If no seed value is provided, the rand() function is automatically seeded with a value of 1.

So here's a quick example:

#include <stdio.h>
#include <stdlib.h>

#define RSEED 2

int main (int argc, char *argv[]) {
  srand(RSEED);
  printf("The random value is %d\n", rand());
  return 0;
}