I would like to add that it's helpful to know in which environment you're trying to run the command. If you're using Windows, the default shell for VSCode's integrated terminal is PowerShell, therefore, you can use the following commands interchangeably to open your files within your workspace as others suggested code -r file_name.rb or code file_name.rb.
Now, if you're using Windows Subsystem for Linux (WSL), you will first need to install the WSL extension in VSCode. Once installed, you can connect to WSL either through "Open a Remote Window" or the "Remote Explorer." This will allow you to switch to your Linux distro within WSL and run the same commands mentioned above to open files within your workspace. Hope this adds some clarity for those of you hacking on Windows.
readlink -f something.phpto print the full path of the file, and then aCtrl+clickon the path open it in a new tab.readlink+Ctrl+clicktrick works as well.