/*------------------------------------------------------------------*/
/* testalarmtimeout.c                                               */
/* The alarm function to implement a timeout.                       */
/* Author: Bob Dondero                                              */
/*------------------------------------------------------------------*/

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <signal.h>
#include <unistd.h>

/*------------------------------------------------------------------*/

static void myHandler(int iSig)

/* This function is intended to be a handler for signals of type
   SIGALRM.  Print a timeout message to stdout, and exit. */

{
   printf("\nSorry.  You took too long.\n");
   exit(EXIT_FAILURE);
}

/*------------------------------------------------------------------*/

int main(void)

/* Illustrate using an alarm to cause a timeout. */

{
   int i;
   void (*pfRet)(int);
   sigset_t sSet;
   int iRet;

   /* Make sure that SIGALRM is not blocked. */
   sigemptyset(&sSet);
   sigaddset(&sSet, SIGALRM);
   iRet = sigprocmask(SIG_UNBLOCK, &sSet, NULL);
   assert(iRet == 0);

   pfRet = signal(SIGALRM, myHandler);
   assert(pfRet != SIG_ERR);

   printf("Enter a number:  ");
   alarm(5);
   scanf("%d", &i);
   alarm(0);

   printf("You entered the number %d.\n", i);
   return 0;
}