til/rails/run-commands-with-specific-rails-version.md

Run Commands With Specific Rails Version

You can have multiple versions of a gem like rails installed with gem. However, when you go to run a rails command, your system will default to using the latest version that you have installed.

So doing a version check will show that version to currently be 7.1.3 and running something like rails new will set up a new Rails 7.1.3 app.

$ rails --version
Rails 7.1.3

$ rails new my_app

If you want to use a Rails version besides the latest you have installed for whatever command, you can use a gem convention which is to put _<VERSION>_ right after the gem name.

Let's try this for Rails 6.1.3:

$ rails _6.1.3_ --version
Rails 6.1.3

$ rails _6.1.3_ new my_app

source