How to find relative path given two absolute paths?

Question

Given two absolute paths, e.g.

• /a/path/to/a
• /a/path/to/somewhere/else

How can I get a relative path from one

Answer 1

Find the longest common path (in this case, /a/path/to) and delete it from both absolute paths. That would give:

• /a
• /somewhere/else

Now, replace each path component in the starting path with ../ and prepend the result to the destination path. If you want to go from directory else to directory a, that would give you:

../../a

If you want to go the other way, you'd instead have:

../somewhere/else