/** sig.c    --- demo how to catch/handle the system signal in C program
 ** by Wen-Nung Tsai.  ** @CopyLeft reserved
 *** gcc sig.c
 *** ./a.out
****** from "man signal":
                 SYNOPSIS
                      #include <signal.h>
                      void (*signal(int sig, void(*func)(int))()
*** In signal(), it will call func in this way:
                 (*func)(sig);
**********************/
extern long time(); /* in <sys/time.h> */
#include <signal.h>
#include <setjmp.h>
#include <stdio.h>
void myisr1(int);  /* an ISR to handle some interrupts */
void myisr2(int tni){printf("he he he!\n");};  /* for other signals */
long k=0, status=0, *p;
jmp_buf env;  /* for use in setjmp(), longjmp() */
int main()
{  /*** tell the system we want to catch some signals ***/
     signal(SIGINT, (void (*)(int)) myisr1 );   /* See K&R Appendix B9 */
     signal(SIGSEGV, *myisr1 ); /* signal(SIGSEGV, (void (*)(int)) myisr1 );*/
     printf("\nWelcome to Disney Land...\n");
     srand(time(0));  /* use current time to set seed of rand() */
     if(rand()%100 < 50){
	if(setjmp(env)==0)     /* See K&R Appendix B8 */
	   *p=38;      /* 這本來應會segmentation fault而引起 core dump ! */
        else goto eoj;     /* 後面的longjmp() 會跑回此處 else ! */
     }
     printf("Here we go!\n");
  loop_a_while:
     while(k<12345){
        printf("%ld ",k++);
     }
     printf("\n=== bye bye ===\n");  return 0;
  eoj:
     system("echo -n Now:"); system("date");
     printf("\n=== abnormal stop:-(\n");  return 1;
}
void myisr1(int x) /* Interrupt Service Routine */
{
   fflush(stdout);  /* try to flush current buffer */
   switch(x){
     case SIGINT:
       printf("\nHey, [sig no=%d] Do NOT hit Control_C\n", x);
       k=12340;
       break;   /* don't forget to take a break :-) */
     default:
       printf("Outch! Seems Segmentation Falt or Fatal error\n");
       status = 49;
       longjmp(env, 123);  /* return a non-zero value */
   } /*switch case*/       /* longjmp() will goto recent if(setjmp... */
   return;
}