Getting the parent of a directory in Bash

Question

If I have a file path such as...

/home/smith/Desktop/Test
/home/smith/Desktop/Test/

How do I change the string so it will be the parent dir

Answer 1

Clearly the parent directory is given by simply appending the dot-dot filename:

/home/smith/Desktop/Test/..     # unresolved path

But you must want the resolved path (an absolute path without any dot-dot path components):

/home/smith/Desktop             # resolved path

The problem with the top answers that use dirname, is that they don't work when you enter a path with dot-dots:

$ dir=~/Library/../Desktop/../..
$ parentdir="$(dirname "$dir")"
$ echo $parentdir
/Users/username/Library/../Desktop/..   # not fully resolved

This is more powerful:

dir=/home/smith/Desktop/Test
parentdir=`(/usr/bin/cd -- "$dir" && pwd)`

You can feed it /home/smith/Desktop/Test/.., but also more complex paths like:

$ dir=~/Library/../Desktop/../..
$ parentdir=`(/usr/bin/cd -- "$dir" && pwd)`
$ echo $parentdir
/Users                                  # the fully resolved path!