Shell

Question 1

What does ${PWD##*/} do?

Answer 1

Finds the longest match of */ starting at the beginning of the string, and removes it. So just the current directory name, not absolute path.

Question 2

What does ${file%.*} do?

Answer 2

Finds the shortest match of .* (which may just be a . ) starting from the end of string and going backwards, and removes it. Most likely this strips an extension (.mp3, .txt, etc).