Bo Berglund wrote:
I am used to the Windows world where you can manage the com port data
prior to actually opening it. Then you use it for a while, close it
and continu other stuff. Later again you can open and use the port.
If one tries to open a port that is either non-existing or already in
use by another program, then there will be an exception.
But in my Linux case where I only have a single com port there was
nothing warning me that the port I opened was not really there...
Hence my problems, I believed that the port was ttyS0 and not
receiving an exception on open enhanced this belief. But in actual
fact only ttyS1 is backed by real hardware, the others are just plain
files by the looks of it. Strange....
No, they're not files.
In the case of gtkterm, does it actually open and use the com port as
soon as it starts? How can it know in advance *which* port the user
wants it to use?
Configuration file.
It makes more sense to me to first specify port number, data speeds
and such and only then open the port, send the data or whatever, and
finally close the port. Then maybe go to another port and repeat the
above...
There's two ways to look at that:
i) Unix doesn't work like that. You need to get a handle for the
device before you can set the Baud rate etc.
ii) Windows doesn't work like that either :-)
Put another way, what you're saying is that you're used to setting up an
object (term used loosely) representing a port before actually doing
something with the port. That's not an OS issue, it's down to the class
library etc.
If hardware access is managed by "lock" files in /var/lock, then what
will happen if the application fails to remove the lock file
afterwards? Do we get a forever unaccessible com port???
I said it was hard work to get right, didn't I?
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
--
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