path

fs.realpath('/etc/passwd', function(err, path) { /* "/private/etc/passwd" */ 
});

dir = path.join('etc', 'passwd');
dir = path.resolve('/etc', 'passwd', '..', 'var');

path.dirname('/etc/passwd')       //=> "/etc"
path.basename('/etc/passwd')      //=> "passwd"
path.basename('/etc/rc.d', '.d')  //=> "rc"

References

• http://nodejs.org/api/path.html