Making things: mkdir and touch

lesson 2-3 · ~8 min · 6/29

Creating directories and files

Every project starts the same way: create a directory skeleton, drop in some starter files, begin working. Doing that with commands instead of clicks means it can be scripted (unit 8) and repeated identically on any machine — including servers, where clicks are not an option.

You've been borrowing these commands since lesson 1-2. Now let's own them:

mkdir name: make directory. Fails if the parent doesn't exist.
mkdir -p a/b/c: the -p flag creates the whole chain of parents in one go, and doesn't complain if some already exist.
touch name: creates an empty file. If the file already exists, it just updates its "last modified" time (that's actually its official job).

Both accept several names at once: touch a.txt b.txt c.txt.

Code exercise · bash

Run it. One mkdir -p builds two directories under site/, touch drops files into them, and ls (with a path argument!) lists each directory without cd-ing into it.

Two ls flags worth knowing now

ls -a: show all entries, including hidden ones. Any name starting with a dot (like .bashrc) is hidden from plain ls. That's the entire hiding mechanism, just a naming convention. You'll meet these "dotfiles" properly in unit 7.
ls -l: long format. One line per entry with permissions, owner, size, and date. The permission string at the start (like -rw-r--r--) is decoded in unit 6.

Flags combine: ls -la shows everything, in detail.

Code exercise · bash

Run it: we create a normal file and a hidden one. Plain ls shows only the visible file. ls -a (filtered to the interesting line with grep, unit 4's star) reveals the hidden one.

Quiz

What does the -p in `mkdir -p app/src/utils` do?

Code exercise · bash

Your turn. Build this project skeleton, then list it: - directories `app/src` and `app/docs` (one mkdir -p) - files `app/readme.md` and `app/src/main.py` - then `ls app` and `ls app/src` Expected output: ``` docs readme.md src main.py ```