Creating and moving files

Why it matters

Setting up a project, organising data files, cleaning up build output, moving logs on a server: all of it is file management, and the terminal does it faster and more repeatably than clicking. It is also less forgiving. The terminal has no recycle bin: a deleted file is gone. This lesson covers the commands and the habits that keep you safe.

Safety rule for this course: practise only inside ~/cli-practice. Never use sudo for these commands, and never aim rm at your home folder or /.

Making folders and files

$ cd ~/cli-practice
$ mkdir project                  # one folder
$ mkdir -p project/data/raw      # -p creates the parent folders too
$ touch project/notes.txt        # empty file (or updates its timestamp)
$ echo "first line" > project/todo.txt   # file with content (more on > next lesson)

Looking at files

$ cat project/todo.txt     # print the whole file
first line
$ less bigfile.txt         # page through: Space = next page, q = quit
$ head -n 5 data.csv       # first 5 lines
$ tail -n 5 app.log        # last 5 lines

cat is fine for short files; use less or head for long ones.

Copying: cp

$ cp project/todo.txt project/todo-backup.txt    # copy a file
$ cp project/todo.txt project/data/              # copy into a folder (keeps the name)
$ cp -r project project-copy                     # -r copies a folder and everything in it

Moving and renaming: mv

mv does both. Moving to a new name in the same folder is renaming:

$ mv project/notes.txt project/meeting-notes.txt   # rename
$ mv project/todo-backup.txt project/data/          # move into a folder

Careful: if the destination file already exists, cp and mv overwrite it without asking. Add -i (interactive) to be asked first: mv -i a.txt b.txt.

Deleting: rm and rmdir

$ rm project/data/todo-backup.txt   # delete a file, permanently
$ rmdir project/data/raw            # delete an EMPTY folder
$ rm -r project-copy                # delete a folder and everything inside
$ rm -i *.tmp                       # ask before each deletion

rm -r is the most dangerous everyday command. Before running it:

1. Run pwd to confirm where you are.
2. Run ls with the same path or pattern first (ls project-copy) to see exactly what would go.
3. Prefer specific paths over wildcardsPatterns such as *.csv or data?.txt that the shell expands to matching file names before the command runs.; use -i when unsure.

You will see rm -rf (force, no questions) in tutorials. Avoid it while learning.

Wildcards

The shell expands patterns before the command runs:

$ ls *.csv          # preview first
$ mv *.csv data/    # then act

Worked example: organise a messy folder

$ cd ~/cli-practice
$ mkdir -p tidy && cd tidy
$ touch jan.csv feb.csv mar.csv notes.txt draft.tmp old.tmp
$ mkdir data
$ ls *.csv
feb.csv  jan.csv  mar.csv
$ mv *.csv data/
$ ls *.tmp
draft.tmp  old.tmp
$ rm -i *.tmp
remove draft.tmp? y
remove old.tmp? y
$ ls -R
.:
data  notes.txt

./data:
feb.csv  jan.csv  mar.csv

&& runs the second command only if the first succeeds, so cd tidy only happens if mkdir worked. ls -R lists folders recursively.

Common mistakes

• rm in the wrong folder. Check pwd first.
• A space in a path: rm my file.txt tries to delete two files, my and file.txt. Quote it: rm "my file.txt".
• Overwriting with mv/cp by accident. Use -i.
• Copying a folder without -r (you get "is a directory" or "omitting directory").

Quick recap

• mkdir -p, touch and echo ... > create; cat, less, head, tail view.
• cp copies (-r for folders); mv moves and renames.
• rm deletes permanently; rm -r deletes folders. Preview with ls, check pwd, use -i.
• Wildcards (*, ?) select many files: always preview them first.

Try it

Open the Do tab to build and reorganise a small project folder.