Distribute Your Software

Overview

Teaching: 5 min
Exercises: 10 min

Questions

• How should I package my software for release?

Objectives

• Explain how and why to describe software dependencies in machine-readable form.

• Explain why development machines should always be set up using package descriptions.

• Package managers support software installation with a single command
  • Handle dependencies recursively
  • Easily scripted/automated
• Motivation: ease software installation burden
  • For users and sysadmins at least
  • Result: a bit more work for the developer(s)
• Describe project dependencies in machine-readable form
  • E.g., Python’s requirements.txt gives package names, and optionally (ranges of) versions

Requirements for a Simple Website

This requirements.txt file specifies that a website needs Django version 1.9.something, any version of PyYAML, and Version 2.0 or later of the requests library. Running pip install -r requirements.txt on the command line will find and install this software.

Django>=1.9,<1.10
PyYAML
requests>=2.0

• Common package managers
  • OS-specific: homebrew, apt, yum, pacman
  • Language-specific: pip, cran, npm, gem, cpan
  • Generic: conda, others?
• Set up development machines using a package manager
  • Doesn’t guarantee that the file is up to date, but it helps
• Use the same package description to install software on users’ machines
• Package managers are often painful to work with
  • Like standards, everybody has their own
  • Often language-specific
  • Often complex (because they’re solving complex problems)
  • Focus on libraries - generally don’t address extra development tools

Ask Your Doctor: Is Packaging Right for You?

1. What language is your project primarily implemented in? Does a package manager exist for this language?
2. Write down your project’s dependencies. Can these be installed with a package manager? Is this the same package manager as above?
3. How do you know if your dependency list is correct? How would you know if something changed and it fell out of date?

Key Points

• Every software ecosystem now includes a package manager to track and update dependencies.

• Describe software versions in precise machine-readable form to take advantage of these.

• Always set up development machines using the package description in order to ensure it’s up to date.