How to return exit code 0 from a failed command

Question

Simply append return 0 to the function to force a function to always exit successful.

function a() {
  ls aaaaa 2>&1
  return 0
}

a
echo $? # prints 0

If you wish to do it inline for any reason you can append || true to the command:

ls aaaaa 2>&1 || true
echo $? # prints 0

If you wish to invert the exit status simple prepend the command with !

! ls aaaaa 2>&1
echo $? # prints 0

! ls /etc/resolv.conf 2>&1
echo $? # prints 1

Also if you state what you are trying to achieve overall we might be able to guide you to better answers.