books/apitue/sample-code/07/sigusr.c

65 lines
1.6 KiB
C

/* This file is part of the sample code and exercises
* used by the class "Advanced Programming in the UNIX
* Environment" taught by Jan Schaumann
* <jschauma@netmeister.org> at Stevens Institute of
* Technology.
*
* This file is in the public domain.
*
* You don't have to, but if you feel like
* acknowledging where you got this code, you may
* reference me by name, email address, or point
* people to the course website:
* https://stevens.netmeister.org/631/
*/
/* A simple program illustrating the implementation of a signal handler.
* Note that we can use the same signal handler for multiple different
* signals.
*/
#include <err.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
static void
sig_usr(int signo) {
if (signo == SIGUSR1)
(void)printf("Nobody expects SIGUSR1!\n");
else if (signo == SIGUSR2)
(void)printf("A surprising turn of events occurred!\n");
else {
(void)fprintf(stderr, "received signal: %d\n", signo);
exit(EXIT_FAILURE);
}
return;
}
int
main(void) {
if (signal(SIGUSR1, sig_usr) == SIG_ERR) {
err(EXIT_FAILURE, "unable to catch SIGUSR1");
/* NOTREACHED */
}
if (signal(SIGUSR2, sig_usr) == SIG_ERR) {
err(EXIT_FAILURE, "unable to catch SIGUSR2");
/* NOTREACHED */
}
if (signal(SIGHUP, sig_usr) == SIG_ERR) {
err(EXIT_FAILURE, "unable to catch SIGHUP");
/* NOTREACHED */
}
(void)printf("%d\n", getpid());
for ( ; ; ) {
pause();
/* Note that the compiler is smart enough to realize we
* don't return from main, so won't warn that we didn't
* return a value. */
}
}