Elixir Cheat Sheet

Elixir cheat sheet with real commands and snippets for setup, core workflows, debugging, and production-safe automation patterns. If you are working across tools, pair this with the PostgreSQL Cheat Sheet and Redis Cheat Sheet.

Setup and Tooling

Goal: Install and verify language toolchain

# Run elixir command
elixir --version

# Run mix command
mix --version

# Run mix command
mix new my_app

Core Workflows

Goal: Run and build source code

# Execute cd workflow
cd my_app && mix run -e 'IO.puts("hi")'

# Execute iex workflow
iex -S mix

Goal: Use a practical code snippet

defmodule Math do
  def double(values) do
    Enum.map(values, fn v -> v * 2 end)
  end
end

IO.inspect(Math.double([1, 2, 3]))

Testing and Formatting

Goal: Run automated tests

# Execute test-related command
mix test

# Execute test-related command
mix test --trace

Goal: Run lint and formatter checks

# Execute quality command
mix format

# Execute quality command
mix credo

Automation and CI

Goal: Create a repeatable CI shell step

# Run strict shell mode for CI step
set -euo pipefail

# Install dependencies deterministically
npm ci || pip install -r requirements.txt || true

# Run tests and fail fast on errors
mix test

Debugging and Troubleshooting

Goal: Trace runtime issues

# Print runtime and package manager versions
node --version || python --version || true

# Search stack traces and TODO markers
rg "Traceback|Exception|TODO" .

# Re-run tests with verbose output
mix test -v || mix test --verbose || true

Common Gotchas

• Pin Elixir language/runtime versions in local and CI environments.
• Keep formatting and linting automated to avoid noisy diffs in code review.
• Prefer explicit dependency lock files for reproducible builds.
• Write small, deterministic tests that can run quickly in pre-commit checks.
• Document compiler/interpreter flags used in production builds.

Related Sheets

• PostgreSQL Cheat Sheet — Postgres schema design and query optimization.
• Redis Cheat Sheet — cache and queue operations.
• Go Cheat Sheet — daily Go commands and production-ready examples.