Сигналы

#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/wait.h>
void sighndlr_1(int signo) { //obrabot4ik dlya 1go processa
    printf("I'm child process #1. I've got SIGINT! :) So, I won't do anything...\n"); //prosto vyvod na ekran soobscheniya o polu4enii signala
}
 
void sighndlr_2(int signo) { //dlhya 2go
    printf("I'm child process #2. I've got SIGINT :)\n");
}
 
int main(int argc, char **argv) {
    pid_t pid1,pid2,pid3,pid4; //4 do4ernih processa
    static struct sigaction act1,act2,act3; //3 struktury dlya 3h processov
    act1.sa_handler = sighndlr_1; //ustanovka obrabot4ika dlya 1 struktory
    act2.sa_handler = sighndlr_2; //dlya 2i
    act3.sa_handler = SIG_IGN; //ignoriruem signal v 3 strukture
    switch(pid1 = fork()) { //sozdaem 1 do4erniy process
    case -1: //vihodim pri oshibke sozdaniya
    printf("Error fork\n");
    exit(1);
    break;
    case 0:
    printf("Child process #1 started (pid = %d)\n", getpid()); //soobshenie ob uspeshnom sozdanii i vyvod pid
    sigaction(SIGINT,&act1,NULL); //ustanovka struktury obrabot4ika dlya SIGINT
    for(;;) pause(); //beskone4nyi cikl
    break;
    default:
    switch(pid2 = fork()) { //sozdaem 2 process
    case -1:
    printf("Error fork\n");
    exit(1);
    break;
    case 0:
    printf("Child process #2 started (pid = %d)\n", getpid());
    sigaction(SIGINT,&act2,NULL); //dlya SIGINT
    sigaction(SIGQUIT,&act3,NULL); //ignorim SIGQUIT
    for(;;) pause();
    break;
    default:
    switch(pid3 = fork()) { //3 process
    case -1:
    printf("Error fork\n");
    exit(1);
    break;
    case 0:
    printf("Child process #3 started (pid = %d)\n", getpid());
    sigaction(SIGINT,&act3,NULL); //ignorim SIGINT
    for(;;) pause();
    break;
    default:
    switch(pid4 = fork()) { //4 process
    case -1:
    printf("Error fork\n");
    exit(1);
    break;
    case 0:
    printf("Child process #4 started (pid = %d)\n", getpid());
    setsid(); //menyaem identifikator seansa dlya processa
    printf("Process #4 changed sid\n");
    for(;;) pause();
    break;
    default:
    printf("Finishing parent process... (pid = %d)\n", getpid());
    exit(0); //zavershaetsya roditelsky process
    break;
    }        
    break;
    }
    break;
    }
    break;
    }