Command line and Git

These are the small commands used throughout the course.

Orient yourself

pwd                 # current directory
ls                  # contents
cd path/to/project  # change directory

Run project commands from the repository root unless documented otherwise.

Inspect files

head data/log.csv
tail data/log.csv
less data/log.csv

Search quickly:

rg "steady_state" .
rg --files

Run Python

uv run python script.py
uv run python script.py --help
uv run pytest tests/test_io.py -q

uv run uses the project environment. Without uv, activate your virtual environment first.

Git state

git status -sb
git diff
git diff --staged
git log --oneline -10

Read the diff before staging.

Branch, stage, commit

git switch -c lesson/clear-description
git add docs/core/03-arrays.md tests/test_analysis.py
git commit -m "Clarify array-shape contract"

Stage explicit files when unrelated work is present. A commit should capture one coherent change and why it exists.

Restore carefully

To discard one unstaged file change:

git restore path/to/file

This is destructive. Inspect git diff -- path/to/file first. Never use git reset --hard as routine tidying.

Pull and push

git pull --ff-only
git push -u origin lesson/clear-description

--ff-only refuses to invent a merge commit when local and remote histories diverge.

Check an output checksum

shasum -a 256 data.csv
shasum -a 256 -c manifest.sha256

Linux may use sha256sum instead.

Useful failure clues

Message	First question
command not found	is the program installed and on PATH?
No such file or directory	what is pwd, and is the path caller-relative?
ModuleNotFoundError	which Python interpreter is active?
Permission denied	are you executing a file that should be passed to Python?
non-zero exit from subprocess	what did stderr say, and which input triggered it?

Do not prefix arbitrary commands with sudo to silence permissions. Understand which resource is protected.