[ILUG] (en?/dis?)-abling modem-control signals on a (not-open) serial port?

[Pádraig Brady]

Brian Foster wrote:
>  what I'm curious about is how the ¬clocal setting is
>  being arranged?  the port's NOT-open, so (I'm guessing)
>  that mysterious something must have done something to
>  arrange for ¬clocal?

Those bits are stateful in the kernel so can be changed
by any program/script that opens it. Note they do default
to a known state at boot. You can (and must) set those bits
(including clocal) before using the port. One can do this
from the command line using the stty command.

Here is a python example where I set CLOCAL specifically so
open() will not hang: http://www.pixelbeat.org/programs/Tira-2/Tira-2.py

A general note, is serial programming is tricky.
I found the following required reading:
http://www.easysw.com/~mike/serial/
http://www.danlj.org/lad/ "Terminals and Pseudo Terminals" chapter

Pádraig.