A StackOverflow [answer][1] with > 3.5K votes features this one-liner for assigning to `DIR` the directory of the current bash script:

 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

I'm puzzled by the nested double-quotes. As far as I can tell, the following fragments are double-quoted:

 "$( cd "
 "${BASH_SOURCE[0]}"
 " && pwd )"

...and everything else to the right of the `=` (i.e. `$( dirname ` and ` )`) is unquoted. In other words, I assume that the 2nd, 4th, and 6th `"` characters "close" the 1st, 3rd, and 5th `"` characters, respectively.

I understand what the double-quotes in `"${BASH_SOURCE[0]}"` achieve, but what's the purpose of the other two pairs of double-quotes?

If, on the other hand (and the high vote score notwithstanding), the above snippet is incorrect, what's the right way to achieve its nominal intent?

(By *nominal intent* I mean: collect the value returned by `pwd` after first `cd`-ing to the directory returned by `dirname "${BASH_SOURCE[0]}"`, and do the `cd`-ing in a sub-shell, so that the `$PWD` of the parent shell remains unchanged).


 [1]: https://stackoverflow.com/a/246128/559827