<!--
title: Environment variable consistency
domain: ml-systems
topic: Configurations
language: Dockerfile
source: comfyanonymous/ComfyUI
updated: 2025-01-11
url: https://awesomereviewers.com/reviewers/comfyui-environment-variable-consistency/
-->

Ensure consistent formatting and proper usage of environment variables in Dockerfiles. Remove unnecessary quotes from ENV declarations and choose between ARG and ENV based on their intended scope - use ARG for build-time configuration that may change between builds, and ENV for runtime configuration that containers need during execution.

Key guidelines:
- Remove unnecessary quotes from ENV values unless the value contains spaces or special characters
- Use ARG for build-time parameters that configure the build process
- Use ENV when the variable needs to be available during container runtime or in RUN commands
- Maintain consistency in formatting across all environment variable declarations

Example:
```dockerfile
# Good - consistent formatting, appropriate usage
ARG PYTHON_VERSION=3.11
ENV PIP_CACHE_DIR=/cache/pip
ENV VIRTUAL_ENV=/app/venv
ENV TRANSFORMERS_CACHE=/app/.cache/transformers

# Avoid - unnecessary quotes and inconsistent formatting  
ENV PIP_CACHE_DIR="/cache/pip"
ENV VIRTUAL_ENV=/app/venv
ENV TRANSFORMERS_CACHE="/app/.cache/transformers"
```

This approach improves readability, reduces confusion about when quotes are necessary, and ensures proper separation between build-time and runtime configuration.