Random numbers

// An example showing how to generate random floating
// point numbers between 0 and 1.

// Michael Ashley / UNSW / 02-Apr-2003

#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

int main(void) {
    struct timeval t;
    int i;

    // Obtain the time of day, to microsecond resolution.

    assert(0 == gettimeofday(&t, NULL)); 

    printf("The time is %ld.%06ld seconds since the Unix epoch\n",
	   t.tv_sec, t.tv_usec);

    // Use the number of microseconds as the seed for the system
    // random number generator.

    srandom(t.tv_usec);
  
    // Generate and print ten random integers between 0 and RAND_MAX.
    
    for (i = 0; i < 10; i++) {
        printf("%ld\n", random());
    }

    // Generate and print ten random numbers between 0 and 1.0.
    
    for (i = 0; i < 10; i++) {
        printf("%.15f\n", random()/((double) RAND_MAX));
    }

    return 0;
}