minix/test/select/test13a.c

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/*
* Test name: test13a.c
*
* Objective: The purpose of this tests is to show how a select can
* get into a race condition when dealing with signals.
*
* Description: The program waits for SIGHUP or input in the terminal
*/
#include <sys/types.h>
#include <sys/select.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>
int got_sighup = 0;
void catch_hup(int sig_num)
{
printf("Received a SIGHUP, set global vble \n");
got_sighup = 1;
}
int main(void) {
int ret; /* return value */
fd_set read_fds;
char data[1024];
/* Init read fd_set */
FD_ZERO(&read_fds);
FD_SET(0, &read_fds);
/* set the HUP signal handler to 'catch_hup' */
signal(SIGHUP, catch_hup);
/* Get proc_id and print it */
printf("Send a signal from other terminal with: kill -1 %d\n", getpid());
printf("Going to sleep for 5 seconds, if the signal arrives meanwhile\n");
printf("the process will be blocked until there is input in the keyboard\n");
printf("if the signal arrives after the timeout and while in select, it will\n");
printf("behave as it should.\n");
printf("Sleeping for 5 secs\n");
sleep(5);
printf("Blocking now on select...\n");
ret = select(1, &read_fds, NULL, NULL, NULL);
if (got_sighup) {
printf("We have a sighup signal so exit the program\n");
exit(0);
}
gets(data);
printf("Got entry for terminal then, bye\n");
}