#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include <wait.h>
#define PCHILD 10

int fd[2];
pid_t pid;
void WaitId();
int con=0;
void SignalHandler(int sig,siginfo_t* info,void* text)
{
    srand(255);
    char c=90;
    write(fd[1],&c,1);
    ++con;
    if(con==3)
        close(fd[1]);
}
int main(int argc,char** argv)
{
 pipe(fd);
 int i=0;
 for(i=0;i<PCHILD;++i)
 {
    pid=fork();
    if(!pid)
    {
        char read[4];
        char write[4];
        sprintf(read,"%d",fd[0]);
        sprintf(write,"%d",fd[1]);
        execlp("./child","child",read,write,(char*)NULL);
        perror("Execlp failed\n");
        exit(-1);
    }
    else if(pid==-1)
    {
        perror("Fork failed\n");
        exit(-1);
    }
 }
 close(fd[0]);

 struct sigaction act;
 sigemptyset(&act.sa_mask);
 act.sa_sigaction=&SignalHandler;
 act.sa_flags=SA_SIGINFO;
 if(sigaction(SIGRTMIN+4,&act,NULL)==-1)
 {

     perror("Sigaction failed\n");
     killpg(getpgrp(),SIGTERM);
 }
 timer_t timerid;
 struct sigevent sevp;
 sevp.sigev_notify=SIGEV_SIGNAL;
 sevp.sigev_signo=SIGRTMIN+4;
 if(timer_create(CLOCK_REALTIME,&sevp,&timerid)==-1)
 {
     perror("timer create failed\n");
     exit(-1);
 }
 struct itimerspec it;
 struct itimerspec it_old;
 it.it_value.tv_sec=0;
 it.it_value.tv_nsec=500000000;
 it.it_interval.tv_sec=0;
 it.it_interval.tv_nsec=500000000;
 if(timer_settime(timerid,0,&it,&it_old)==-1)
 {
    printf("timer_settime failed\n");
    errno;
    killpg(getpgrp(),SIGTERM);
 }
   int ret;
   siginfo_t info;
   while(1)
   {
         ret=waitid(P_ALL,0,&info,WEXITED|WSTOPPED|WCONTINUED|WNOHANG);
         if(ret==-1)
                break;
         if(!ret && info.si_pid)
               printf("PID:%d Status:%d\n",info.si_pid,info.si_status);
   }
 close(fd[1]);
 return 0;
}















#define _GNU_SOURCE
#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <errno.h>
#include <time.h>
#include <wait.h>
#include <poll.h>

int main(int argc,char** argv)
{
 char* end1=NULL;
 char* end2=NULL;
 int rd=strtol(argv[1],&end1,10);
 int wr=strtol(argv[2],&end2,10);
 if(end1==argv[1] || end2==argv[2])
     exit(-1);
 if(fcntl(rd,F_GETFD)==-1 || fcntl(wr,F_GETFD)==-1 || errno==EBADF)
 {
     perror("File descriptor read or write is invalid\n");
     exit(-1);
 }
 time_t start,end;
 struct pollfd fds;
 fds.fd=rd;
 fds.events=POLLIN;
 struct timespec tm;
 tm.tv_sec=0;
 tm.tv_nsec=500000000;
 while(1)
 {
     char c;
     if(ppoll(&fds,1,&tm,NULL)>0)
     {
        read(rd,&c,1);
        time(&start);
        struct timespec req;
        if(c>48)
        {
            write(1,&c,1);
            (int)c--;
            write(wr,&c,1);
            time(&end);
        }
        req.tv_sec=0;
        req.tv_nsec=1000000;
        nanosleep(&req,NULL);
     }
     else
     {
        close(wr);
        close(rd);
        exit(0);
     }
 }

 return 1 ;
}