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 [[ $OSTYPE == darwin* ]]; then
  # macOS
elif [[ "$(</proc/sys/kernel/osrelease)" == *microsoft* ]]; then
  # WSL2
else
  # Other *nix distro.
fi

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.}

Answer 2

Updating answer by @per-lundberg:

if [[ ! -z "$IS_WSL" && ! -z "$WSL_DISTRO_NAME" ]]; then
    echo "You are not in wsl!"
else
    echo "You are in wsl!"
fi

Note: IS_WSL existed in older verion while WSL_DISTRO_NAME exist in current version.

Answer 3

For WSL2, we can no longer detect through kernel version because it is running an actual Linux kernel in Hyper-V. However, it still can call explorer.exe existing in every Windows installation. So we could...

if [ -x "$(command -v explorer.exe)" ]; then
echo "We are running on WSL"
fi

This should be a more generic way to detect if the script is running on WSL.

Edit: See answers above. I forgot to count Unix-like environments like Msys2 in.

Answer 4

Here's what I put in my .bashrc

if [[ $(uname -v | sed -rE 's/^#[0-9]{3,}-(\S+).+/\1/') == "Microsoft" ]]; then
  # WSL-specific code
fi

• uname -v gets the kernel version in the format of #379-Microsoft Wed Mar 06 19:16:00 PST 2019 and the sed expression pulls out the Microsoft string.

Answer 5

Without me doing anything special, these environment variables seem to be set already:

$ set | grep WSL
IS_WSL='Linux version 4.4.0-18362-Microsoft (Microsoft@Microsoft.com) (gcc version 5.4.0 (GCC) ) #1-Microsoft Mon Mar 18 12:02:00 PST 2019'
WSLENV=
WSL_DISTRO_NAME=Debian

So, something like the following snippet should also work in this case (example of what I used it for myself):

if [ ! -z "$IS_WSL" ]; then
    alias code='/mnt/c/Users/per/AppData/Local/Programs/Microsoft\ VS\ Code/Code.exe'
fi

(Note that technically, -z does not check if the variable is unset, merely that it is empty; in practice, this works well enough in this case. The ! at the beginning is there to negate the check.)

Answer 6

I've been looking for ways to detect that as well. So far I've found 2.

• /proc/sys/kernel/osrelease is "3.4.0-Microsoft"

• /proc/version is "Linux version 3.4.0-Microsoft (Microsoft@Microsoft.com) (gcc version 4.7 (GCC) ) #1 SMP PREEMPT Wed Dec 31 14:42:53 PST 2014"

If you just use the Ubuntu distribution installed by default there should be no problems with using them, as they said that it would be unlikely for them to set either to something that doesn't contain "Microsoft" or "WSL".

However, if you were to install a different Linux distribution, I'm pretty sure that the contents of /proc/sys/kernel/osrelease and /proc/version will change, since the distro wouldn't have been compiled by Microsoft.