. is here, .. is up
Every folder contains two pointers: . means this folder and .. means the one above. They work anywhere a path does.
Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.
What it is for
../data, ./run.sh, cd ../..: these appear in every README and every script, and they only make sense once the two dots are second nature.
How to think about it
Read a path piece by piece: .. climbs one level, then whatever follows the slash. ./name says 'the one right here', which is how you run a file in this folder.
Worked example
mkdir -p demo/a/b && cd demo/a/bThree levels down.
ls ..The folder above is a, and it contains b.
cd ../..Up two.
pwdEnds in /demo.
Your turn
List the folder above this one.
ls
Try it at a real prompt
The trap
Typing cd .. as cd. or cd . . and wondering why nothing happened. Two dots, no space, is one name.
Practise . and .. on HoneA question on it now, a coding challenge where there is one, and it is remembered for review. Free, no email needed.