#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <execinfo.h>

int         g_sigstop = 0; 

void signal_stop(int signum)
{
	if( SIGTERM == signum )
	{
		printf("SIGTERM signal detected\n");
	}
	else if( SIGALRM == signum )
	{
		printf("SIGALRM signal detected\n");
		g_sigstop = 1;
	}
}

void signal_user(int signum)
{
	if(SIGUSR1 == signum)
	{
		printf("SIGUSR1 signal detected\n");
	}
	else if(SIGUSR2 == signum)
	{
		printf("SIGUSR2 signal detected\n");
	}

	g_sigstop = 1;
}

void signal_code(int signum)
{
	if(SIGBUS == signum)
	{
		printf("SIGBUS signal detected\n");
	}
	else if(SIGILL == signum)
	{
		printf("SIGILL signal detected\n");
	}
	else if(SIGSEGV == signum)
	{
		printf("SIGSEGV signal detected\n");
	}

	exit(-1);
}

int main(int argc, char **argv)
{
	char                 *ptr=NULL;
	struct sigaction      sigact, sigign;

	/*+--------------------------------------+
	 *| Method1: Use signal() install signal |
	 *+--------------------------------------+*/

	signal(SIGTERM, signal_stop);
	signal(SIGALRM, signal_stop);

	signal(SIGBUS, signal_code);
	signal(SIGILL, signal_code);
	signal(SIGSEGV, signal_code);

	/*+-----------------------------------------+
	 *| Method2: Use sigaction() install signal |
	 *+-----------------------------------------+*/

	/*  Initialize the catch signal structure. */
       	sigemptyset(&sigact.sa_mask);
       	sigact.sa_flags = 0;
       	sigact.sa_handler = signal_user;

	/*  Setup the ignore signal. */
       	sigemptyset(&sigign.sa_mask);
       	sigign.sa_flags = 0;
       	sigign.sa_handler = SIG_IGN; 
	
	sigaction(SIGINT, &sigign, 0); /*  ignore SIGINT signal by CTRL+C */

       	sigaction(SIGUSR1,  &sigact, 0); /*  catch SIGUSR1 */
       	sigaction(SIGUSR2,  &sigact, 0); /*  catch SIGUSR1 */


	printf("Program start running for 20 seconds...\n");
	alarm(20);

	while( !g_sigstop )
	{
		;
	}

	printf("Program start stop running...\n");

	printf("Invalid pointer operator will raise SIGSEGV signal\n");
	*ptr = 'h';

	return 0;
}