Creating, Copying, Moving, Linking, and Deleting

Making things

mkdir makes directories, one or several at once ¹:

me@linuxbox:~$ mkdir projects
me@linuxbox:~$ mkdir drafts finished archive
me@linuxbox:~$ mkdir -p garden/2027/seeds     # -p makes the missing parents too

touch creates an empty file if it doesn’t exist (and updates the time on one that does):

me@linuxbox:~$ touch notes.txt

You’ll make real files with editors and redirection soon; touch is for quick test files.

Copying

cp copies ¹:

me@linuxbox:~$ cp notes.txt notes-backup.txt         # file to new file
me@linuxbox:~$ cp notes.txt drafts/                  # file into a folder
me@linuxbox:~$ cp a.txt b.txt c.txt drafts/          # several files into a folder
me@linuxbox:~$ cp -r garden garden-backup            # a whole folder

The options worth knowing ¹:

That silent overwrite is the trap: cp draft.txt final.txt replaces final.txt without a word if it already exists ¹.

Moving and renaming

mv moves and renames, and they’re the same operation ^{1 2}:

me@linuxbox:~$ mv notes.txt garden-notes.txt     # rename
me@linuxbox:~$ mv garden-notes.txt garden/       # move into a folder
me@linuxbox:~$ mv drafts finished/               # move a whole folder (no -r needed)

On the same disk, mv doesn’t copy any data; it just changes the name and where it’s listed, so moving a 40 GB folder is instant. Across disks it copies, then deletes the original ². Like cp, it overwrites silently unless you add -i ¹.

Deleting for good

rm removes files; rm -r removes a directory and everything in it; rmdir removes only an empty directory ^{1 3}.

me@linuxbox:~$ rm old-notes.txt
me@linuxbox:~$ rm -r garden-backup

There is no trash and no undelete ¹. The file’s name is gone the moment you press Enter. (The bytes may linger on the disk until something overwrites them, which matters for privacy, not for getting your file back ³.) Habits that save you:

• rm -i asks about each file; rm -I asks once before removing more than three files or anything recursive ³.
• Test a wildcard with ls first, then press up-arrow and change ls to rm ¹.
• Be most careful with rm -rf: -f (force) never asks and ignores errors ¹. Read the line twice before pressing Enter.

The classic disaster: you mean rm *.html and type rm * .html. The stray space makes two arguments, * (every file here) and .html, so rm deletes everything and then complains that .html doesn’t exist ¹.

Wildcards

Wildcards let one command name many files. The shell expands them into the matching names before the command runs ¹:

Examples ¹:

me@linuxbox:~$ ls photos/IMG_2026*.jpg          # check first
me@linuxbox:~$ mv photos/IMG_2026*.jpg photos/2026/

Wildcards don’t match hidden dot-files unless the pattern starts with a dot.

Links

A file’s name isn’t the file. The data lives on disk, and a directory just holds names that point to it. Links add more names ^{1 4}:

• A hard link (ln target newname) is another name for the very same file; the two are indistinguishable. Delete one and the data stays until its last name is gone. That’s what the link count in ls -l counts. Hard links can’t point to directories or reach across disks ^{1 4}.
• A symbolic link (ln -s target newname) is a tiny file that holds a path. Programs that open it are sent to the target, like a Windows shortcut. It can point at a directory or another disk, but if the target is moved or deleted, the link breaks and points at nothing ^{1 4}.

me@linuxbox:~$ ln -s ~/garden/2027/seeds seeds
me@linuxbox:~$ ls -l seeds
lrwxrwxrwx 1 me me 25 Oct  5 08:10 seeds -> /home/me/garden/2027/seeds
me@linuxbox:~$ cd seeds        # takes you into the real folder

Symbolic links are what you’ll use: shortcuts to deep folders, and the way Linux keeps several versions of something with one stable name. Your system is full of them (ls -l /bin) ¹.

Your turn: a playground

So

mkdir, touch, cp, and mv make, copy, and move things, and both cp and mv overwrite silently unless you add -i. rm is permanent, so test wildcards with ls first. Wildcards are expanded by the shell before the command runs. Hard links are extra names for the same data; symbolic links are pointers by path that break when the target moves.