/*	alarm2.cpp
	an alarm example using multiple process
*/
#include <sys/types.h>
#include <wait.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	pid_t pid;
	int seconds;
	char line[128];
	char message[64];

	while(1) {
		printf("Alarm>");
		if (fgets(line, sizeof (line), stdin) == NULL) exit(0);
		if (strlen (line) <=1) continue;
		
		/* parse input line into seconds (%d) and a message
		 * (%64[^\n]), consisting of up to 64 characters 
		 * separated from the seconds by whitespace.
		 */
		if (sscanf(line, "%d %64[^\n]",
		    &seconds, message ) <2 ) {
		    fprintf( stderr, "Bad Command\n");
		}
		else {
		    pid =  fork();
		    if (pid == (pid_t) -1 ) {
 			printf("fork() error!\n");
			exit(1);
		    }
		    if ( pid == (pid_t)0) {
			/* this is the child, wait and then print a message */
		    	sleep (seconds);
		    	printf( "(%d) %s\n", seconds, message);
			exit(0);
		    }
		    else {
			/* this is parent, call waitpid() to collect children
			 * that have already terminated.
			 */
			do {
				pid = waitpid ((pid_t) -1, NULL, WNOHANG);
				if (pid == (pid)-1) {
					printf("Wait for child!\n");
					exit(1);
				}
			}while( pid != (pid_t) 0);
		    }
		}
	}
}