Add Run Commands With Specific Rails Version as a Rails TIL

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

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+# 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.
+
+```bash
+$ 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:
+
+```bash
+$ rails _6.1.3_ --version
+Rails 6.1.3
+
+$ rails _6.1.3_ new my_app
+```
+
+[source](https://stackoverflow.com/a/452458/535590)