Re: read-write to stdin-stdout or to a file?

[Pedro Zorzenon Neto <pzn@terra.com.br>]

On Fri, Jul 20, 2001 at 12:42:13PM +0100, David Wright wrote:
> Do you mean this package?
> 
> "Programmer for Atmel AVR microcontrolers that uses PC parallel port

Yes.

> If so, I'm not sure why you think it needs to be setuid. Just
> chgrp somegroup /dev/lp0 (or whichever port) and put yourself
> (and any others) into somegroup.

I tried /dev/lp* and couldn't make the program work with it.

This program uses a specific hardware connected to the printer port. It has to read some bits of the port and write other bits in patterns which has to change in some microseconds.

That is why it uses lowlevel ioperm, inb, outb to IO 0x378 (or other IO, at user option[1]) and runs setuid root.

I think (not sure about all architectures) that because of this, it will run only in i386 machines. If I used /dev/lp* it would run in all machines. If someone knows how to use lp device for this specific purpose, please write me.

  Thanks,
  Pedro

[1] root must edit a config file to say which ports the user can choose.