manual/examples/sigh1.c

   1 /* Signal Handlers that Return
   2    Copyright (C) 1991-2014 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License
   6    as published by the Free Software Foundation; either version 2
   7    of the License, or (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, if not, see <http://www.gnu.org/licenses/>.
  16 */
  17
  18 #include <signal.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21
  22 /* This flag controls termination of the main loop. */
  23 volatile sig_atomic_t keep_going = 1;
  24
  25 /* The signal handler just clears the flag and re-enables itself. */
  26 void
  27 catch_alarm (int sig)
  28 {
  29   keep_going = 0;
  30   signal (sig, catch_alarm);
  31 }
  32
  33 void
  34 do_stuff (void)
  35 {
  36   puts ("Doing stuff while waiting for alarm....");
  37 }
  38
  39 int
  40 main (void)
  41 {
  42   /* Establish a handler for SIGALRM signals. */
  43   signal (SIGALRM, catch_alarm);
  44
  45   /* Set an alarm to go off in a little while. */
  46   alarm (2);
  47
  48   /* Check the flag once in a while to see when to quit. */
  49   while (keep_going)
  50     do_stuff ();
  51
  52   return EXIT_SUCCESS;
  53 }