Design Rule Checking

Kudos to the guy who first thought of, and implemented  "DRC".
It works very well right up to the time a designer produces gerber files.
But after that, we're on our own.

I understand that some Fab shops have the capability to run a DRC against the
customer supplied gerber files. Sometimes spacing errors are found. But how
could this be? Are cad operators not paying attention to their post-processing
reports? or are they changing apertures during the gerber process? or are Fab
shops changing aperture sizes and then running DRC's?

I would be happy to run a DRC against my gerber files, but I have yet to see
a cad system that can do it. We can simulate the artwork-select a .001 grid-
and then view the simulation. But this is error prone and could make you go
blind.

Does software exist for a dos/unix system to run a DRC against the gerber files?
I don't care about neat graphics, just a program that will allow me to check
proper spacing of artwork features.

Al Slagle
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