#include <pthread.h>
#include <stdio.h>

int sum; /* this data is shared by the thread(s) */
void *runner(void * param); /* the thread */

main (int argc, char *argv[]) {
	pthread_t tid; /* the thread identifier */
	pthread_attr_t attr; /* set of thread attributes */
	if (argc != 2) {
		fprintf(stderr, "usage: 5-5 <integer value>\n");
		exit(-1);
	}
	if (atoi(argv[1]) < 0) {
		fprintf(stderr, "%d must be <= 0\n", atoi(argv[1]));
		exit(-1);
	}
	/* get the default attributes */
	pthread_attr_init(&attr);
	/* create the thread */
	pthread_create(&tid, &attr, runner, argv[1]);
	/* now wait for the thread to exit */
	pthread_join(tid, NULL);
	printf("sum = %d\n", sum);
}

/* The thread will begin control in this function */
void *runner (void *param) {
	int upper = atoi(param);
	int i;
	sum = 0;
	if (upper > 0) {
		for (i = 1; i <= upper; i++)
			sum += i;
	}
	pthread_exit(0);
}