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Published November 3, 2016 Updated October 1, 2023
Runcom Icon



Runcom is a Run Command portmanteau (i.e. run + [com]mand = runcom) which provides common functionality for Command Line Interfaces (CLIs) in which to manage global/local caches, configurations, data, and/or state. It does this by leveraging the XDG Base Directory Specification built atop the XDG implementation. In other words, Runcom is an enhanced version of XDG.


  • Wraps the XDG implementation which provides access to the following environment variables:







  • Enhances the XDG cache, config, data, and state implementations.



To install with security, run:

# 💡 Skip this line if you already have the public certificate installed.
gem cert --add <(curl --compressed --location
gem install runcom --trust-policy HighSecurity

To install without security, run:

gem install runcom

You can also add the gem directly to your project:

bundle add runcom

Once the gem is installed, you only need to require it:

require "runcom"


The following describes the enhancements built atop the XDG implementation.


While there isn’t an environment convenience object as found with the XDG gem, you can instantiate each object individually:

cache = "demo/data.json"
config = "demo/configuration.yml"
data = "demo/store.dat"
state = "demo/history.log"

💡 By default, each Runcom object expects a relative path but you can use a fully qualified path as well.

Each of the above objects share the same Object API:

  • #relative: Answers the relative path from which the object was constructed.

  • #namespace: Answers the namespace as a pathname object from which the instance was constructed. The namespace must be unique and identical across the cache, config, data, and state objects since this is what identifies and organizes all files associated with your program.

  • #file_name: Answers the file name from which the object was constructed.

  • #active: Answers first existing file path as computed by $XDG_*_HOME followed by each computed $XDG_*_DIRS path in order defined. Otherwise, nil is answered back when no path exists.

  • #passive: Answers first path as computed by $XDG_*_HOME followed by each computed $XDG_*_DIRS path in order defined which may or may not exist. This behaves like #active but doesn’t care if the path exists. Handy for situations where you’d like the active path but can fallback to creating the global path if otherwise.

  • #global: Answers the first existing or non-existing global path only.

  • #local: Answers the first existing or non-existing local path only.

  • #all: Answers all paths which is the combined $XDG_*_HOME and $XDG_*_DIRS values in order defined. These paths may or may not exist.

  • #inspect: Answers a string representation of default XDG home and directory paths for debugging purposes.

Using a cache object, for example, here is what each method answers back:

cache = "demo/content.json"

cache.relative   # => #<Pathname:demo/content.json>
cache.namespace  # #<Pathname:demo>
cache.file_name  # #<Pathname:content.json>     # nil
cache.passive    # #<Pathname:/Users/demo/.cache/demo/content.json>     # #<Pathname:/Users/demo/.cache/demo/content.json>
cache.local      # #<Pathname:/Users/demo/Engineering/OSS/runcom/.cache/demo/content.json>
cache.all        # [#<Pathname:/Users/demo/Engineering/OSS/runcom/.cache/demo/content.json>, #<Pathname:/Users/demo/.cache/demo/content.json>]
cache.inspect    # "XDG_CACHE_HOME=/Users/demo/Engineering/OSS/runcom/.cache:/Users/demo/.cache"

Variable Priority

Path precedence is determined in the following order (with the first taking highest priority):

  1. Local Configuration - If a $XDG_*_HOME or $XDG_*_DIRS path relative to the current working directory is detected, it will take precedence over the global configuration. This is the same behavior as found in Git where the local .git/config takes precedence over the global $HOME/.gitconfig.

  2. Global Configuration - When a local configuration isn’t found, the global configuration is used as defined by the XDG Base Directory Specification.

Building Blocks

While XDG and Runcom are powerful in their own right, a great building block you can add on top of this gem is the Etcher gem which loads, transforms, validates, and produces structured data from raw Runcom information. For more sophisticated applications, this synergetic coupling of XDG + Runcom + Etcher makes for nicely designed architectures.


Examples of gems built atop this gem are:

  • Rubysmith: A command line interface for smithing Ruby projects.

  • Gemsmith: A command line interface for smithing new Ruby gems.

  • Hanamismith: A command line interace for smithing Hanami projects.

  • Git Lint: Enforces consistent Git commits.

  • Milestoner: A command line interface for releasing Git repository milestones.

  • Pennyworth: A command line interface that enhances and extends Alfred with Ruby support.

  • Pragmater: A command line interface for managing/formatting source file pragma comments.

  • Sublime Text Kit: A command line interface for managing Sublime Text metadata.

  • Tocer: A command line interface for generating Markdown table of contents.


To contribute, run:

git clone
cd runcom

You can also use the IRB console for direct access to all objects:



To test, run: