B09 Lab week 4

I teach several courses, and I have taught and will teach them over several years and terms. Should I organize my course directories by years and then by courses?

2017/B63
2018/B63
2018/C24
2019/B09
2019/C24

Or should I organize them by courses and then by years?

B09/2019
B63/2017
B63/2018
C24/2018
C24/2019

Every couple of years, I change my mind and switch from one scheme to the other! Help me automate this. Write a shell script ‘transpose.sh’ to:

Take 2 command line arguments. They are assumed to be directory names. I'll refer to them as src and tgt respectively below.
If the user gives fewer than 2 arguments, write to stderr an error/reminder message (exact message up to you), and exit with exit code 1.
Attempt to create directory tgt.
If mkdir fails (likely because tgt already exists), write to stderr an error message (exact message up to you), and exit with exit code 2.
Copy src content to tgt, but switching the scheme along the way. For example, if I have
```
src/2017/B63
src/2018/B63
src/2018/C24
src/2019/B09
src/2019/C24
```
then the copying should result in
```
tgt/B09/2019
tgt/B63/2017
tgt/B63/2018
tgt/C24/2018
tgt/C24/2019
```
Reminder: ‘cp -R’ can copy a whole directory.
You may not create/write any other file/directory, and you shouldn't need to. Automarking will happen in a docker container where only tgt (and under) is writable.

You may assume:

src is an existing directory, and there are really two levels of directories below src. Those directory names don't start with dots. (But there can be dot files further down!)
tgt ≠ src
The user has enough permission for the required operations.

You may get good help from a program called ‘basename’. By way of example, ‘basename foo/bar/quartz’ outputs ‘quartz’ to stdout. (Now how do you capture that into your own variable so you can use it later?)

I have prepared a sample tree (YC.zip); also on Mathlab at

/courses/courses/cscb09s23/laialber/l04/YC

and you may test with, for example

sh transpose.sh /courses/courses/cscb09s23/laialber/l04/YC mytgt

and then see if you get good results under ‘mytgt’, e.g., compare with my CY directory (also as CY.zip):

diff -ru mytgt /courses/courses/cscb09s23/laialber/l04/CY

What to hand in: transpose.sh