promptNonNull

# -*-shell-script-*-
# Prompt user for info but don't accept the empty string
#
# TODO 2015-02-12: generalize; make a version that will
#   accept empty, will loop until it gets non-empty, etc.
function promptNonNull () {
  # args:
  #  prompt (string)     User prompt. Append a trailing space if desired.
  #  variable (varname)  Name of variable in which to store response.
  local answer="${(P)2}"
  vared -p "$1" -c answer
  if [[ -n "${answer}" ]]; then
    typeset -g "${2}"="${answer}"
  else
    echoerr "$0: null response setting $2."
    return 1
  fi
  return 0
}