Date: Tue, 22 Jun 1999 17:11:14 +0200 (ZAT) From: "Andre Pekelaar" <andre@ct.paywise.co.za> To: Jean-Michel DRICOT <jdricot@ulb.ac.be>, questions@freeBSD.org Subject: Parallel Port File Descriptor problem Message-ID: <199906221513.RAA03521@ct.paywise.co.za>
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> Date: Mon, 21 Jun 1999 18:50:30 +0200
> From: Jean-Michel DRICOT <jdricot@ulb.ac.be>
>
> I've put correct permissions (say 777) on /dev/lpt0 and tried using
> file descriptor, like in my old LINUX Box :-) with "/dev/lp0" . As
> non-root user this time I tried executing:
>
> int fd=open("/dev/lpt0",O_RDWR);
> write(fd,...........);
>
> But my fd was always <0 (error with IOPerm.) even if executed the
> program as root....
>
> How can I get a valid FD to a parllel port in order to use
> write(fd,.......) ?
Since you presumably only want to WRITE to the port, not READ from +
WRITE to it, have you tried the following:
int fd=open("/dev/lpt0",O_WRONLY);
In other words, change O_RDWR to O_WRONLY.
I would guess that your problem is that although you appear to have
all the relevant permissions, the LPT device driver does not support
being opened for reading, hence the "permissions" problem.
Hope this helps,
Andre
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Andre Pekelaar <andre@ct.paywise.co.za>
Manager, Development Department Paywise Software Products (Pty) Ltd
Tel: +27-21-7628720 PO Box 24, Plumstead, 7801
Fax: +27-21-7628726 Cape Town
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