Files and Directories

You can now find your way around. This lesson is about changing things — making files and folders, copying them, moving them, and deleting them.

One of these operations is permanent. We'll get to that.

Making things

touch creates an empty file (or, if it already exists, quietly updates its timestamp without touching the contents):

touch notes.txt

mkdir creates a directory:

mkdir projects

mkdir fails if the parent doesn't exist. mkdir -p creates the whole chain, and doesn't complain if some of it is already there:

mkdir -p projects/website/src

That -p is why you'll see mkdir -p in nearly every setup script ever written — it's safe to run twice, which is a property worth wanting in anything automated.

Notice touch took two arguments and made two files. Most commands accept as many as you give them.

Copying and moving

cp copies, mv moves. Both take the source first and the destination second:

cp notes.txt notes-backup.txt
mv notes.txt archive/

Two things trip people up:

Copying a directory needs -r. By default cp refuses to copy a folder, because copying a tree is a different and much larger operation than copying one file. -r (recursive) says "yes, the whole thing":

cp -r site/ site-backup/

mv is also how you rename. There is no rename command in the way you'd expect. Moving a file to a new name in the same directory is a rename:

mv draft.txt final.txt

That's not a hack — it's the same operation. A file's name is just an entry in a directory, so changing the name and changing the directory are the same kind of change.

Deleting, and the thing nobody warns you about

rm removes files. rm -r removes directories and everything inside them.

rm notes.txt
rm -r old-project/

Here is the part that matters: there is no trash can. rm does not move things aside for later recovery. It unlinks them, and the space becomes available for reuse. On a normal filesystem with no backups, a deleted file is gone.

This is not a flaw. The command line assumes you meant what you said. But it means a typo in an rm command is in a different category of mistake than a typo anywhere else.

Two habits that will save you:

1. Run ls with the same argument first. If ls old-* lists what you expect, then rm -r old-* will delete what you expect. If it lists something surprising, you just avoided a bad afternoon.
2. Use rm -i when deleting with wildcards. It asks before each file. Tedious, and worth it when the pattern is doing the choosing rather than you.

Next: actually reading what's inside these files.