/*
 * Program: pause_suspend.c
 *  To test the difference between sigsuspend() and paus().
 * Author: zsl
 * Date: 2014-10-17
 * First release.
 * 参见网页：http://blog.csdn.net/liwentao1091/article/details/6619089
 * 
 * */
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>

/*
 * Handler for SIGINT (Ctrl-C), SIGQUIT (Ctrl-\)
 * */
void sig_func(int signo)
{
    if ( SIGINT == signo )	// just print a line.
    {
	printf(" SIGINT is processing...\n ");
    }
    if ( SIGQUIT == signo )	// print a line and exit.
    {
	printf(" SIGQUIT is processing ...\n ");
	printf(" Now exiting ...\n ");
	exit(EXIT_SUCCESS);
    }
}

int main(void)
{
    int i;
    sigset_t maskset, set_quit;

    sigemptyset(&maskset);
    sigemptyset(&set_quit);	// initialize two sets.
    sigaddset(&maskset, SIGINT); // mask SIGINT
    sigaddset(&set_quit, SIGQUIT); // suspend SIGQUIT
    // signal the two signals: SIGINT, SIGQUIT
    signal(SIGINT, sig_func);
    signal(SIGQUIT, sig_func);

    while(1)
    {
	/* First to mask the signal of the process: SIGINT */
	sigprocmask(SIG_BLOCK, &maskset, NULL);
	for(i = 0; i < 10; i ++)
	{
	    write(1, "*  ", strlen("*  "));
	    sleep(1);
	}

	printf("\n");
#if 1
	/*
	 * while sigsuspend(), SIGQUIT is blocked.
	 * but SIGINT is unblocked.
	 * If you want to execute the two signals, you 
	 * should Ctrl-\, then Ctrl-C.
	 * */
	printf("Before sigsuspend() ... \n");
	sigsuspend(&set_quit);
#else
	sigprocmask(SIG_UNBLOCK, &maskset, NULL);
	pause();
#endif
    }

    return 0;
}