test/select/test13a.c

   1 /*
   2  * Test name: test13a.c
   3  *
   4  * Objective: The purpose of this tests is to show how a select can
   5  * get into a race condition when dealing with signals.
   6  *
   7  * Description: The program waits for SIGHUP or input in the terminal
   8  */
   9
  10 #include <sys/types.h>
  11 #include <sys/select.h>
  12 #include <stdlib.h>
  13 #include <unistd.h>
  14 #include <time.h>
  15 #include <stdio.h>
  16 #include <signal.h>
  17 #include <errno.h>
  18
  19 int got_sighup = 0;
  20
  21 void catch_hup(int sig_num)
  22 {
  23         printf("Received a SIGHUP, set global vble \n");
  24         got_sighup = 1;
  25 }
  26
  27 int main(void) {
  28         int ret;                /* return value */
  29         fd_set read_fds;
  30         char data[1024];
  31
  32         /* Init read fd_set */
  33         FD_ZERO(&read_fds);
  34         FD_SET(0, &read_fds);
  35
  36         /* set the HUP signal handler to 'catch_hup' */
  37         signal(SIGHUP, catch_hup);
  38
  39         /* Get proc_id and print it */
  40         printf("Send a signal from other terminal with: kill -1 %d\n", getpid());
  41         printf("Going to sleep for 5 seconds, if the signal arrives meanwhile\n");
  42         printf("the process will be blocked until there is input in the keyboard\n");
  43         printf("if the signal arrives after the timeout and while in select, it will\n");
  44         printf("behave as it should.\n");
  45         printf("Sleeping for 5 secs\n");
  46         sleep(5);
  47
  48         printf("Blocking now on select...\n");
  49         ret = select(1, &read_fds, NULL, NULL, NULL);
  50         if (got_sighup) {
  51                 printf("We have a sighup signal so exit the program\n");
  52                 exit(0);
  53         }
  54         gets(data);
  55         printf("Got entry for terminal then, bye\n");
  56 }