/*
 * program to show random number generation
 * prints the number of random numbers indicated by command line argument
 *
 * Matt Bishop, ECS 36A, Fall Quarter 2019
 */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

/*
 * function prototypesl shoulkdbe declared nb stdlib.h but aren't
 */
void srandom(unsigned int);
long random(void);

/*
 * main routine
 */
int main(int argc, char *argv[])
{
	int i;			/* counter in a for loop */
	int n;			/* value of command line argument */
	long int prn;		/* pseudorndom number */
	char *aend;		/* points just beyond where number found */
	time_t t;		/* current time; used to seed the PRNG */

	/*
	 * check there is a second argument
	 */
	if (argc != 2){
		fprintf(stderr, "Usage: %s number\n", argv[0]);
		return(1);
	}

	/*
	 * convert that to an integer and check for error
	 */
	n = strtol(argv[1], &aend, 10);
	if (*aend != '\0'){
		/* extra stuff at the end */
		fprintf(stderr, "Usage: %s number\n", argv[0]);
		return(1);
	}
	/* it's a number -- be sure it's positive */
	if (n <= 0){
		fprintf(stderr, "A *positive* integer please!!!\n");
		return(1);
	}

	/*
	 * now we know how many pseudorandom numbers to print
	 *
	 * next, seed the pseudorandom number generator (PNRG)
	 */
	if ((t = time(NULL)) == -1){
		perror("time");
		return(1);
	}
	srandom((unsigned int) t);

	/*
	 * generate and print them
	 */
	printf("First column is number from random()\n");
	printf("Second column is a random number between 0 and 99 inclusive\n");
	printf("Third column is a random number between -50 and 50 inclusive\n");
	for(i = 0; i < n; i++){
		prn = random();
		printf("%10ld\t%3ld\t%3ld\n", prn, prn % 100, prn % 101 - 50);
	}

	/*
	 * bye!
	 */
	return(0);
}