manual/examples/sigusr.c

   1 /*@group*/
   2 #include <signal.h>
   3 #include <stdio.h>
   4 #include <sys/types.h>
   5 #include <unistd.h>
   6 /*@end group*/
   7
   8 /* When a @code{SIGUSR1} signal arrives, set this variable.  */
   9 volatile sig_atomic_t usr_interrupt = 0;
  10
  11 void
  12 synch_signal (int sig)
  13 {
  14   usr_interrupt = 1;
  15 }
  16
  17 /* The child process executes this function. */
  18 void
  19 child_function (void)
  20 {
  21   /* Perform initialization. */
  22   printf ("I'm here!!!  My pid is %d.\n", (int) getpid ());
  23
  24   /* Let parent know you're done. */
  25   kill (getppid (), SIGUSR1);
  26
  27   /* Continue with execution. */
  28   puts ("Bye, now....");
  29   exit (0);
  30 }
  31
  32 int
  33 main (void)
  34 {
  35   struct sigaction usr_action;
  36   sigset_t block_mask;
  37   pid_t child_id;
  38
  39   /* Establish the signal handler. */
  40   sigfillset (&block_mask);
  41   usr_action.sa_handler = synch_signal;
  42   usr_action.sa_mask = block_mask;
  43   usr_action.sa_flags = 0;
  44   sigaction (SIGUSR1, &usr_action, NULL);
  45
  46   /* Create the child process. */
  47   child_id = fork ();
  48   if (child_id == 0)
  49     child_function ();          /* Does not return.  */
  50
  51 /*@group*/
  52   /* Busy wait for the child to send a signal. */
  53   while (!usr_interrupt)
  54     ;
  55 /*@end group*/
  56
  57   /* Now continue execution. */
  58   puts ("That's all, folks!");
  59
  60   return 0;
  61 }