/*--------------------------------------------------------------------*/
/* testalarm.c                                                        */
/* Author: Bob Dondero                                                */
/*--------------------------------------------------------------------*/

#define _GNU_SOURCE

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

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

/* This function is intended to be a handler for signals of type
   SIGALRM.  Write a message to stdout that contains iSignal, the 
   number of the signal that caused the function to be called.  Then
   reset the alarm. */

static void myHandler(int iSignal)
{
   /* Really shouldn't call printf() here. See Bryant & O'Hallaron
      page 766. */
   printf("In myHandler with parameter %d.\n", iSignal);
   
   /* Reset the alarm. */
   alarm(2);
}

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

/* Demonstrate the alarm() function.  As usual, argc is the
   command-line argument count, and argv contains the command-line
   arguments.  The function never returns. */

int main(int argc, char *argv[])
{
   const char *pcPgmName;
   void (*pfRet)(int);

   pcPgmName = argv[0];

   /* Install myHandler as the handler for SIGALRM signals. */
   pfRet = signal(SIGALRM, myHandler);
   if (pfRet == SIG_ERR) {perror(pcPgmName); exit(EXIT_FAILURE); }

   /* Set a 2 second alarm.  After 2 seconds of real time, send a
      SIGALRM signal to this process. */
   alarm(2);

   /* Enter an infinite loop. */
   printf("Entering an infinite loop\n");
   for (;;)
      sleep(1);

   /* Will not reach this point. */
}

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

/* Sample execution:

$ gcc217 testalarm.c -o testalarm

$ ./testalarm
Entering an infinite loop
In myHandler with parameter 14.
In myHandler with parameter 14.
In myHandler with parameter 14.
In myHandler with parameter 14.
^C

*/