Hi,
How can i link a user defined M code to an output.
For example i want to use M120 in my nc program to let a parport output go high
Can i than put this same output low by another user defined m code ?

IIRC - in your m120 script you would put halcmd setp pinname true... or something like that. You would have to play with it. This is not realtime though.. So it depends on what you are trying to do. If what you want is very time sensitive.. - I would look at m62-m65

http://www.linuxcnc.org/docs/2.2/html/gcode_main.html#sec:M62-to-M65:

sam