Kernel status script

When developing on Arch Linux, kernel updates happen pretty frequently. For most things, this is fine and I can continue working. For some things, notably Docker, I need to reboot my machine after the kernel is updated. This probably depends on what storage driver you use and such, but currently I use overlayfs which is loaded by the kernel. You might be able to get away with just modprobe but I tend to just restart as it's quick and easy.

To remind myself when this happens, I wrote this script:

#!/bin/bash

[[ `pacman --query linux` =~ ^(.*)([0-9]+[0-9]?\.[0-9]+[0-9]?\.[0-9]+[0-9]?)(.*)$ ]] && installed_kernel=${BASH_REMATCH[2]};

[[ `uname --kernel-release` =~ ^(.*)([0-9]+[0-9]?\.[0-9]+[0-9]?\.[0-9]+[0-9]?)(.*)$ ]] && running_kernel=${BASH_REMATCH[2]};

if [[ "$running_kernel" != "$installed_kernel" ]];
then
  echo "Restart ($installed_kernel)"
else
  printf "OK ($running_kernel)"
fi

This will print out OK (5.3.1) if my installed kernel matches the running one, or Restart (5.3.1) if my running kernel is older. Then I added the script to my path and call it in xmobar config like so:

Run Com "kernelstatus" [] "kernel" 1000

And now I can see it in my status bar:

The kernel status

I haven't figured out an easy way to color the output of a custom command like this in xmobar (without dusting off my Haskell skills), but will update if I do.

Update (2019-11-12): Arch changed the version string returned by pacman --query linux to no longer contain the word arch, so here's an updated script:

#!/bin/bash

# e.g. linux 5.3.10.1-1
[[ `pacman --query linux` =~ ^(.*)([0-9]+[0-9]?\.[0-9]+[0-9]?\.[0-9]+[0-9]?)(\.[0-9]+-[0-9]+)(.*)$ ]] && installed_kernel=${BASH_REMATCH[2]};

# e.g. 5.3.10-arch1-1
[[ `uname --kernel-release` =~ ^(.*)([0-9]+[0-9]?\.[0-9]+[0-9]?\.[0-9]+[0-9]?)(.*)$ ]] && running_kernel=${BASH_REMATCH[2]};

if [[ "$running_kernel" != "$installed_kernel" ]];
then
  echo "Restart ($installed_kernel)"
else
  printf "OK ($running_kernel)"
fi