What is the Unix command to create a hardlink to a directory in OS X?

Question

How do you create a hardlink (as opposed to a symlink or a Mac OS alias) in OS X that points to a directory? I already know the command \"ln target destination\" but that on

Answer 1

The short answer is you can't. :) (except possibly as root, when it would be more accurate to say you shouldn't.)

Unixes only allow a set number of links to directories - ".." from within all its children and "." from within itself. Anything else is potentially a recipe for a very confused directory tree. This is/was apparently a design decision by Ken Thompson.

(Having said that, apparently Apple's Time Machine does do this :) )

Answer 2

You can't do it directly in BASH then. However... I found an article here that discusses how to do it indirectly: http://www.mactech.com/articles/mactech/Vol.23/23.11/ExploringLeopardwithDTrace/index.html by compiling a simple little C program:

#include <unistd.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
   if (argc != 3) return 1;

   int ret = link(argv[1], argv[2]);

   if (ret != 0) perror("link");

   return ret;
}

...and build in Terminal.app with:

$ gcc -o hlink hlink.c -Wall