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Created February 26, 2012 01:23
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A Common .ruby-version File For Ruby Projects

A Common .ruby-version File For Ruby Projects


I've been using this technique in most of my Ruby projects lately where Ruby versions are required:

  • Create .rbenv-version containing the target Ruby using a definition name defined in ruby-build (example below). These strings are a proper subset of RVM Ruby string names so far...
  • Create .rvmrc (with rvm --create --rvmrc "1.9.3@myapp") and edit the environment_id= line to fetch the Ruby version from .rbenv-version (example below).

Today I learned about another Ruby manager, rbfu, where the author is using a similar technique with .rbfu-version.


What if we had an ecosystem of fabulous Ruby managers that all understood the semantics of a generic dotfile such as .ruby-version? The file's contents would be nothing more than a string representing a version of Ruby.

Perhaps We Can

Without a more thorough investigation (here be dragons?), the project-level updates might be:

  • rvm: A modification to scripts/functions/rvmrc to check for .rvmrc and then .ruby-version (invoking something like rvm use $(cat $working_dir/.ruby-version)). If the user requires a customized .rvmrc they can wire in .ruby-version themselves (i.e. environment_id="$(cat .ruby-version)@gemset").
  • rbenv: A modification to libexec/rbenv-version-file to check for .rbenv-version and then .ruby-version.
  • rbfu: A modifcation to bin/rbfu to first check for .rbfu-version and then .ruby-version.

In all 3 cases, it seems reasonable to prefer an implementation-specific file over the generic version--no loss of default behavior.


Feedback? Ideas? Questions?

#!/usr/bin/env bash
# This is an RVM Project .rvmrc file, used to automatically load the ruby
# development environment upon cd'ing into the directory
# First we specify our desired <ruby>[@<gemset>], the @gemset name is optional,
# Only full ruby name is supported here, for short names use:
# echo "rvm use 1.9.3" > .rvmrc
environment_id="$(cat .rbenv-version)@myapp"
# Uncomment the following lines if you want to verify rvm version per project
# rvmrc_rvm_version="1.10.3" # 1.10.1 seams as a safe start
# eval "$(echo ${rvm_version}.${rvmrc_rvm_version} | awk -F. '{print "[[ "$1*65536+$2*256+$3" -ge "$4*65536+$5*256+$6" ]]"}' )" || {
# echo "This .rvmrc file requires at least RVM ${rvmrc_rvm_version}, aborting loading."
# return 1
# }
# First we attempt to load the desired environment directly from the environment
# file. This is very fast and efficient compared to running through the entire
# CLI and selector. If you want feedback on which environment was used then
# insert the word 'use' after --create as this triggers verbose mode.
if [[ -d "${rvm_path:-$HOME/.rvm}/environments"
&& -s "${rvm_path:-$HOME/.rvm}/environments/$environment_id" ]]
\. "${rvm_path:-$HOME/.rvm}/environments/$environment_id"
[[ -s "${rvm_path:-$HOME/.rvm}/hooks/after_use" ]] &&
\. "${rvm_path:-$HOME/.rvm}/hooks/after_use" || true
# If the environment file has not yet been created, use the RVM CLI to select.
rvm --create "$environment_id" || {
echo "Failed to create RVM environment '${environment_id}'."
return 1
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andyw8 commented Jan 2, 2024

Specification for .ruby-version (rubygems discussion).

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