How to rename nested folders?

Question

So I have a bunch of folders in the format of: .../course/year/... and I often reorganize them so that the format then changes to this: .../year/course/.... I've been meaning to learn how to write shell scripts and I'm very new to automation and shell scripting but I want to make a script that does this for me when I input a path to the folder that I want renamed. So for example I would have a command like: sh reorganize.sh .../course/year/... and it would "swap" the course folder and the year folder. The year folder has some contents inside and after the swap everything that was in the year folder should now be in the course folder. There are also multiple year folders, so 2018, 2019, 2020 each have their own folder inside the course folder. I appreciate any help with how I can go about doing this.

PS- When I say I'm fairly new, what I mean is that I know the basic behind variables and pipes and basic commands but don't have much knowledge otherwise.

Answer 1

#! /bin/bash

rootdir="$PWD"
shopt -s nullglob

for course in *; do
    pushd "$course" >/dev/null
    for year in *; do
        mkdir -p "${rootdir}/${year}"
        mv --no-target-directory "$year" "${rootdir}/${year}/${course}"
    done
    popd >/dev/null
    rmdir "$course"
done

When jumping between directories I consider it less error-prone to work with absolute paths (rootdir="$PWD") and pushd/popd instead of cd. Though this rather simple case does not demand that.

The mv --no-target-directory shall prevent unexpected effects if the script runs several times (with the former run aborting). Again, one could argue that in this case (moving within a filesystem) the dangerous case cannot occur. mv behaves differently depending on whether the target directory / new path exists or not. This option prevents that.