Week 1 – Command Line, Environments and Git

Overview

Week 1 builds the foundation every developer uses every day: navigating the filesystem from the terminal, understanding how the shell resolves commands, managing configuration through environment variables, and tracking work with Git. The week ends with a real project hosted on GitHub and deployed through a CI pipeline.

What you will learn

Objectives

By the end of this week you will be able to:

• Navigate and manipulate the filesystem entirely from the terminal.
• Read and modify file permissions, and write executable shell scripts.
• Explain what $PATH is, how the shell searches it, and how to add your own commands to it.
• Create, export, and persist environment variables across sessions.
• Explain the difference between Git and GitHub, and between GitHub and alternative hosting services.
• Execute the full Git workflow: init, add, commit, branch, merge, and resolve conflicts.
• Write commit messages that follow the Conventional Commits specification.
• Choose between merge, squash, and rebase strategies and explain the trade-offs.
• Open a pull request, review it, and merge it on GitHub.
• Write a basic GitHub Actions workflow that reads environment variables and runs a script.

Topics

Terminal and Shell

• Core commands: pwd, ls, cd, mkdir, touch, echo, cat, cp, mv, rm, rmdir
• File permissions: read, write, execute; chmod +x
• Writing and running a shell script with a shebang line
• The rm -rf hazard and safe alternatives

The PATH

• What $PATH is and how the shell searches it left to right
• which to locate a command; export to extend the path for a session
• ~/.zshrc vs ~/.zprofile — interactive vs login shell config
• source to reload a config file without reopening the terminal
• Creating a personal ~/bin directory with a custom command

Environment Variables

• What environment variables are and how programs read them
• env, export, unset; the difference between a shell variable and an exported variable
• ${VAR:-default} syntax for safe fallbacks
• .env files and why they must never be committed
• The APP_ENV convention: local, dev, staging, production
• set -a && source .env && set +a to load a .env file

Git and Version Control

• Git vs GitHub; GitHub vs GitLab, Bitbucket, Azure DevOps
• Core workflow: git init, git add, git commit, git log, git diff
• git add -p for intentional, hunk-level staging
• Conventional Commits: feat, fix, docs, chore, refactor, test, ci
• Branching: git switch -c, git merge, merge conflicts and resolution
• Merge strategies: merge commit (--no-ff), squash merge, rebase
• git stash and git stash pop
• .gitignore patterns

GitHub Workflow and CI

• Creating and cloning a repository on GitHub
• Pushing a branch and opening a pull request
• PR descriptions: what changed, why, and how to test
• Merging with Squash and merge for a linear history
• GitHub Actions: workflow syntax, on: triggers, env: variables, workflow_dispatch
• Running a bash script in CI with environment variables supplied by the workflow

Deliverables

• A working ~/bin directory with at least one custom command on the PATH.
• A bash script that changes behaviour based on an environment variable.
• A envar-demo repository on GitHub with:
  • A bin/app-info script that reads three environment variables
  • A .env.example file
  • A .gitignore excluding .env
  • At least two merged pull requests with Conventional Commit messages
  • A GitHub Actions workflow that runs the script in CI