/* newnamespace.c */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sched.h>
#include <sys/types.h>
#include <sys/wait.h>

typedef struct {
  char *path;
  char **argv;
} FuncInfo;

int childfn(void *p) {
  FuncInfo *fi = (FuncInfo *)p;

  /*  setenv("PS1", "@@ ", 1); */
  execv(fi->path, fi->argv);
  perror("execl");
  fprintf(stderr, "Cannot exec '%s'\n", fi->path);
  exit(1);
}

static char *default_path = "/bin/ash";
static char *default_argv[] = {"ash", NULL};

int main(int argc, char *argv[]) {
  char buf[10000];
  pid_t pid, p;
  
  FuncInfo fi;

  if (argc == 1) {
    /* No arguments given */
    fi.path = default_path;
    fi.argv = default_argv;
  } else {
    int i;
    argc--; argv++;
    fi.path = *argv;
    fi.argv = (char **)malloc(sizeof(char *) * (argc + 1));
    for (i = 0; i < argc; i++) {
      fi.argv[i] = argv[i];
    }
    fi.argv[argc] = NULL;
  }

  pid = clone(childfn, buf + 5000, CLONE_NEWNS | SIGCHLD, &fi);
  if ((int) pid == -1) {
    perror("clone");
    exit(1);
  }
  
  p = waitpid(pid, NULL, 0);
  if ((int) p == -1) {
    perror("waitpid");
    exit(1);
  }
  
  exit(0);
}