Get rid of null character in vim variable?

Some alternatives:

1. Remove the \n using substitute(string, '\n$', '', '') See :h NL-used-for-Nul for the technical background

2. Remove all control chars: substitute(string, '[[:cntrl:]]', '', 'g')

3. Compare using the match (=~) operation instead of equal (==)

4. Strip away the last byte of the output from the system() command

   :let a=system('foobar')[:-2]