How to check if a program is run in Bash on Ubuntu on Windows and not just plain Ubuntu?

Question

Pretty straightforward, the usual places to figure out the OS you\'re on seem to be identical to plain Ubuntu on Ubuntu for Windows. For example uname -a is ide

Answer 1

I needed to test for macOS in addition to Windows Subsystem for Linux 2.

This is the simplest thing working for us.

if [[ $OSTYPE == darwin* ]]; then
  # macOS
elif [[ "$(

NOTE: The if order matters. On macOS you get this error when looking at proc/version.
_{/proc/version: No such file or directory}

_{hat-tip @Niklas Holm and @Marc Cornellà in the top answer's comments for aiming me toward the correct WSL check.}