лабораторки по ОС препод Челноков / 2семестр / wi2 / chernok / lab33 / 33

/***************************************************************************
                          main.c  -  description
                             -------------------
    begin                : уТД нБК  5 03:27:25 MSD 2004
    copyright            : (C) 2004 by бМЕЛУЕК
    email                : achernok@mail.ru
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <signal.h>
static int onsigint(int sig);
static int onsigusr1(int sig);
static int onsigusr2(int sig);
static int onsigusr3(int sig);
static pid_t fpid,spid,tpid;
pid_t fd[2];
int mes;
int main(int argc, char *argv[])
{
  signal(SIGINT,&onsigint);
  pipe(fd);
  switch(fpid=fork())
  {
    case -1:printf("FORK ERROR\n");
    case  0:fpid=getpid();
            switch(spid=fork())
            {
              case -1:printf("FORK ERROR\n");
              case 0:
                spid=getpid();
                switch(tpid=fork())
                {
                  case -1:printf("FORK ERROR\n");
                  case  0:
                    tpid=getpid();
                    signal(SIGUSR1,&onsigusr3);
                    while(1)
                      pause();
                  default:
                    signal(SIGUSR1,&onsigusr2);
                    while(1)
                      pause();
                }

                default:
                  signal(SIGUSR1,&onsigusr1);
                  mes=1;
                  write(fd[1],&mes,sizeof(mes));
                  sleep(1);
                  kill(spid,SIGUSR1);
                  while(1)
                    pause();
             }
    default:while(1)
              pause();
  }
}
int onsigint(int sig)
{
  signal(SIGINT,&onsigint);
  printf("Recieved signal to abort process %d\n",getpid());
  exit(0);
}

int onsigusr1(int sig)
{
   signal(SIGUSR1,&onsigusr1);
   read(fd[0],&mes,sizeof(mes));
   printf("FIRST  process recieved: %d from THIRD  process\n",mes);
   mes=mes+1;
   write(fd[1],&mes,sizeof(mes));
   sleep(1);
   kill(spid,SIGUSR1);
   return EXIT_SUCCESS;
   
}
int onsigusr2(int sig)
{
   signal(SIGUSR1,&onsigusr2);
   read(fd[0],&mes,sizeof(mes));
   printf("SECOND process recieved: %d from FIRST  process\n",mes);
   mes=mes+1;
   write(fd[1],&mes,sizeof(mes));
   sleep(1);
   kill(tpid,SIGUSR1);
   return EXIT_SUCCESS;
}
int onsigusr3(int sig)
{
   signal(SIGUSR1,&onsigusr3);
   read(fd[0],&mes,sizeof(mes));
   printf("THIRD  process recieved: %d from SECOND process\n",mes);
   mes=mes+1;
   write(fd[1],&mes,sizeof(mes));
   sleep(1);
   kill(fpid,SIGUSR1);
   return EXIT_SUCCESS;
}