#include <unistd.h> // fork, write, close, sleep
#include <fcntl.h> // open
#include <stdio.h> // perror

int main(int argc, char* argv[]) {
	pid_t f = fork();
	int file = open("test.txt", O_WRONLY);
	if (file < 0) {
		perror("open");
		return 1;
	}

	if (f == 0) { // in child
		char buf = 'c';
		for (int i = 0; i < 5; i++) {
			sleep(2);
			if(write(file, &buf, 1) < 0) {
				perror("write");
				return 2;
			}
		}
	}
	else {
		char buf = 'p';
		for (int i = 0; i < 5; i++) {
			if(write(file, &buf, 1) < 0) {
				perror("write");
				return 3;
			}
			sleep(1);
		}
	}
	close(file);
}