chruby

As Ruby is an interpreter most executables just have "#!/usr/bin/env ruby" at the top of the file. If you have multiple versions of Ruby, this may or may not pick up the correct version you have installed. Historically the interpreter has made quite a few breaking changes, didn't follow semantic versioning and didn't care about backwards compatibility. What these tools do is alter the environment so that you can 'lock' specific versions of the interpreter. The same problem also occurs with libraries, which may also have their own executables, so these tools have tried to solve both problems - which is slightly more complicated than a three line shell script. Bundler has become the standard way of managing libraries, so now something like chruby[0] can be used to do pretty much what you said for the interpreter alone. Of course the other t

Also try the postmodern tools: ruby-install & chruby, which work perfectly in my experience: https://github.com/postmodern/ruby-install https://github.com/postmodern/chruby

Another excellent tool for the same problem is chruby[1]. I found it simpler (in a good way) than rbenv. [1] https://github.com/postmodern/chruby

As someone who tried RVM for a while and until it's problems became obvious, and lived (very successfully) with rbenv as an escape for a long time afterwords, I have been liking chruby: https://github.com/postmodern/chruby It doesn't have most of the problems of RVM/rbenv, and mainly provides an easy way to switch between rubies while leaving everything else as full-path references instead of the "magic" tht RVM tries to provide. That said, I really like the local $GEM_HOME method, and guix sounds like an interesting solution.

While I'm not familiar with python & virtualenv, the problem of that would be solved by putting rails in a container (isolating the ruby environment in a fairly easily deployable way) was solved many years ago with Gemfiles/bundler[1] that pin your dependencies, and the various ways of deploying multiple rubies. RVM does indeed suck hard, but rbenv[2] is very simple (I've used it personally to develop and deploy a few projects). One of the preferred ways to deploy rails is (was? I did this ~2 years ago) was to check it in with git and the name/version of the ruby environment to use is stored in the file ".rbenv-version", with dependencies managed by bundler (which you point to a local gem server). Install is then 1) use rbenv/ruby-install to install basic ruby, 2) install app with "git clone", and 3) run bundler. Many tools exist to do th