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

int main (int argc, char** argv) {
	
	int status;
	pid_t child_pid;
	
	child_pid = fork();
	
	switch (child_pid) {
		
		// fork error
		case -1: 
			perror("fork");
			return EXIT_FAILURE;
		
		// child code
		case 0: {
			printf("Child here. My pid is %d. Parent's pid is %d\n", getpid(), getppid());
			
			const char *args[] = {"/bin/echo", "Changed the process with a new one by using execv", NULL};
            execv("/bin/echo", (char *const *)args);
			//execlp("echo", "echo", "Changed the process with a new one by using execlp", NULL);
			
			printf("If this code is reached, then exec has caused an error (for example the file to be executed was not found)\n");
            break;
		}
		
		// parent code
		default: {
			
			printf("Parent here. My pid is %d. Child's pid is %d\n", getpid(), child_pid);
			
			// wait for child to end execution
			pid_t waited_pid = waitpid(child_pid, &status, 0);
			if (waited_pid < 0) {
				perror("waitpid");
				return EXIT_FAILURE;
			}
			printf("Parent here. Succesfully waited for child %d\n", waited_pid);
		}
	}

	return 0;
}