* Backtick `...` substitutes an OS command's stdout into a .control line,
* the ngspice equivalent of shell command substitution.
R1 1 0 1k
V1 1 0 DC 5
.op
.control
  run
  set nwords = `echo one two three four five | wc -w`
  echo "the shell counted $nwords words"
  let total = $nwords * 2
  print total
.endc
.end
