simple unshared mount namespace

#include <stdio.h>
#include <string.h>
#include <sched.h>
#include <linux/sched.h>
#include <unistd.h>

int main() {
  int ret;
  if (ret = unshare(CLONE_NEWNS) != 0) {
    fprintf(stderr, "ERROR: unshare returned: %s\n", strerror(ret));
    _exit(1);
  }
  printf("unshared into new mount namespace\n");
  printf("sleeping for 1000\n");
  sleep(1000);
}