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

The following works in bash on Windows 10, macOS, and Linux:

#!/bin/bash
set -e
if grep -qEi "(Microsoft|WSL)" /proc/version &> /dev/null ; then
    echo "Windows 10 Bash"
else
    echo "Anything else"
fi

You need to check for both "Microsoft" and "WSL" per this comment by Ben Hillis, WSL Developer:

For the time being this is probably the best way to do it. I can't promise that we'll never change the content of these ProcFs files, but I think it's unlikely we'll change it to something that doesn't contain "Microsoft" or "WSL".

/proc/sys/kernel/osrelease
/proc/version

And case shall be ignored for grep. In WSL2, /proc/version gives lowercased microsoft.

Answer 2

Windows Subsystem for Linux 2 (WSL 2) in Windows 10 Pro Insider Preview Build 18917

/proc/version contains:

Linux version 4.19.43-microsoft-standard (oe-user@oe-host) (gcc version 7.3.0 (GCC)) #1 SMP...

Answer 3

I just came up with this for my .bashrc for adding some WSL items to $PATH.

Works in 1703. Not sure if earlier versions.

if [[ $(uname -r) =~ Microsoft$ ]]; then
    foo
fi

Answer 4

If you in Bash and want to avoid fork:

is_wsl=0
read os </proc/sys/kernel/osrelease || :
if [[ "$os" == *Microsoft ]]; then
  is_wsl=1
fi