unix0104b

#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#define TIMEOUT 10
extern int f1(int), f2(int), f3(int);
int pid0, pid1, pid2;
void main(void)
{
    setpgrp();
    pid0 = getpid();
    pid1 = fork();
    if (pid1 == 0) /* process 1 */
    {
        signal(SIGUSR1, f1);
        pid1 = getpid();
        pid2 = fork();
        if (pid2 < 0 ) puts("Fork error");
        if (pid2 > 0) for(;;);
        else /* process 2 */
        {
            signal(SIGUSR2, f2);
            pid2 = getpid();
            kill(pid1,SIGUSR1);
            for (;;);
        }
    }
    else /* process 0 */
    {
        signal(SIGALRM, f3);
        alarm(TIMEOUT);
        pause();
    }
    exit(0);
}
int f1(int signum)
{
    signal(SIGUSR1, f1);
    printf("Process 1 (%d) has got à signal from process 2 (%d)\n",pid1,pid2);
    sleep(1);
    kill(pid2, SIGUSR2);
    return 0;
}
int f2(int signum)
{
    signal(SIGUSR2, f2);
    printf("Process 2 (%d) has got à signal from process 1 (%d)\n",pid2,pid1);
    sleep(1);
    kill(pid1, SIGUSR1);
    return 0;
}
int f3(int signum)
{
    printf("End of job - %d\n", pid0);
    kill(0, SIGKILL);
    return 0;
}