#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <fcntl.h>

int main(int argc, char* argv[]){
	int i;
	int fd, pid;
	
	fd = open("lockf.c", O_RDONLY);
	fflush(NULL);
	srand(time(NULL));
	for(i = 0; i<6; i++){
		pid = fork();
		
		if(pid>0) continue;
		if(pid==0){
			printf("try to lock %d\n", getpid());
			lockf(fd, F_LOCK, 0);
			printf("got lock %d\n", getpid());
			sleep(2);
			lockf(fd, F_ULOCK, 0);
			exit(0);
		}
	}
	wait(NULL);
	
	return 0;
}