Preamble / Postamble

Hi,
I have CNC router with TB6600 drivers directly controlled by parallel port (through opto-isolators for safety).
I was using USBCNC and it was awful cause I was getting too many random usb resets (disconnects).

Is there any way to tell LinuxCNC to append a preamble and/or postamble to a job?
Say I have created a gcode file from Aspire (which does not support preamble/postamble append) and I want to run it with LinuxCNC. Can LinuxCNC append a standard finishing code, like move z up 20mm and goto XY home ?

Thanks for your time.

Thank you very much BigJohnT. This is exactly what I was looking for.

Aspire can prepend/append preamble/postamble.
In PP you can write what will be at the beginning and end of g-code file.