#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#define NR_OPEN 1048576

int main(void) {
    // create new process
    pid_t pid = fork();
    if (pid == -1) {
        return -1;
    } else if (pid != 0) {
        printf("Running daemon with pid %d\n", pid);
        exit(EXIT_SUCCESS);
    }

    // create a new session and process group
    if (setsid() == -1) return -1;

    // set the working directory to the root directory
    if (chdir("/") == -1) return -1;

    // close all open files--NR_OPEN is overkill, but works
    for (int i = 0; i < NR_OPEN; i++) { 
        close(i);
    }

    // redirect fd's 0,1,2 to /dev/null
    open("/dev/null", O_RDWR); // stdin
    dup(0);                    // stdout
    dup(0);                    // stderr

    // do its daemon thing
    for (int i = 0; i < 10; i++) {
        printf("Hello from daemon %d\n", getpid());
        sleep(1000);
    }

    return 0;
}