/////////////////////////////////////////////////////////////////////////////
// Rev 11/12/2003                                               
// 
// 
//                             SIGNAL.C
//                             --------
// 
// 
// Sylvain MARECHAL - sylvain.marechal1@libertysurf.fr
/////////////////////////////////////////////////////////////////////////////
// 
//  Show signal usage
// 
/////////////////////////////////////////////////////////////////////////////
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#define SIG_STOP_CHILD SIGUSR1
main()
{
    pid_t pid;
    sigset_t newmask, oldmask;
    if ((pid = fork()) == 0) 
    {  /*Child*/
	struct sigaction action;
	void catchit();
	sigemptyset(&newmask);
	sigaddset(&newmask, SIG_STOP_CHILD);
	sigprocmask(SIG_BLOCK, &newmask, &oldmask);
	action.sa_flags = 0;
	action.sa_handler = catchit;
	if (sigaction(SIG_STOP_CHILD, &action, NULL) == -1) 
	{
	    perror("sigusr: sigaction");
	    _exit(1);
	}
	printf( "Signal is blocked\n" );
	sleep(5);
	printf( "Signal is unblocked\n" );
	sigprocmask(SIG_UNBLOCK, &newmask, NULL);
	sleep(5);
	/*sigsuspend(&oldmask);*/
	printf( "Exiting ...\n" );
    }
    else 
    { /* Parent */
	int stat; int i;
	sleep(1);
	for( i = 0; i < 10; i ++ )
	    kill(pid, SIG_STOP_CHILD);
	pid = wait(&stat);
	printf("Child exit status = %d\n", WEXITSTATUS(stat));
	_exit(0);
    }
}
void catchit(int signo)
{
    printf("Signal %d received from parent\n", signo);
    /*_exit(0);*/
}