The command line has no undo and simple typing mistakes will ruin your data and can leave the Mac in a worse state (even breaking single user mode). It may be possible to use 'single user mode' to delete files, however I strongly suggest you do that AFTER taking a full backup as I just described (assuming you want to go that route). You are running the Mac with too little free space - that is how you get into messes like this. all the applications or an entire users data). Migration assistant doesn't really help with that process unless you are willing to avoid migrating a broad category of data (e.g.
I understand that you can't delete files with a non booting OS, but simply backing up & restoring won't help unless you remove some files during that process.
