code: function ctrlAPI(stop, newCbk) {//{{{
  
          // Ignore calls after spinning finished:
          if (stopped) return false;
  
          // Make stop parameter optinal:
          if ("boolean" != typeof stop) {
              newCbk = stop;
              stop = undefined;
          };
  
          // Message string/callback updating operation:
          if (newCbk !== undefined) {
              // Accept callback or literal string:
              messageCbk = ("function" == typeof newCbk)
                  ? newCbk
                  : ()=>newCbk
              ;
              if (! is_tty) {
                  if (stop !== undefined) {
                      stop || process.stdout.write("\n");
                  } else {
                      console.log(symbols.arrow + ' ' + messageCbk(false));
                  };
              };
          };
  
          // Handle Stopping operation:
          if (stop !== undefined) {
              clearInterval(next);
              stopped = true;
  
              let s = symbols[stop ? "ok" : "error"];
              logUpdate(s + ' ' + messageCbk(true));
  
              if (is_tty) process.stdout.write("\n");
          }
  
          return true; // Success.
  
      }
docs: }}}