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#include <assert.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/wait.h>
static void noop(int x) {
(void)x;
}
int main() {
signal(SIGUSR1, &noop);
int pid;
switch(pid = fork()) {
case -1:
perror("fork");
abort();
case 0:
pause();
assert(errno == EINTR);
return 0;
default:
while (1) {
usleep(100);
kill(pid, SIGUSR1);
usleep(100);
int status;
errno = 0;
if (waitpid(-1, &status, WNOHANG) <= 0) {
if (errno && errno != EAGAIN) {
perror("wait");
kill(pid, SIGKILL);
}
continue;
}
if (!WIFEXITED(status)) {
printf("wait returned %x\n", status);
abort();
}
return WEXITSTATUS(status);
}
}
}
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