make G code display error

I want to make G code display error when something happens.

e.g. if M66 times out on a signal, instead. of moving on, it should display an error and stop the program. Or if when a prob value is over the tolerance, it should error out, display a message and stop

Is there a way to do it?

thanks

rogerxue wrote: it should error out, display a message and stop

Use In the G-code.

(this is one of a number of "magic comments" available in LinuxCNC. The brackets are important)