Restricted shell for SSH tunnel users

#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
void sig_handler(int signo)
{
    if (signo == SIGHUP)
        exit(0);
}

int main()
{
    printf("OK\n");
    while(1)
        sleep(1);
    exit(0);
}