Re: /dev/ttyX not-blocking

From: Theodore Y. Ts'o (tytso@MIT.EDU)
Date: Sun Jul 30 2000 - 05:41:30 EST


   Date: Sat, 29 Jul 2000 23:07:51 -0400 (EDT)
   From: Edward Muller <edwardam@home.com>

   Nevermind 'stty -F /dev/ttyS1 -clocal' fixed the problem. Although
   I'm not sure why the device was setup with clocal, which disables
   modem control signals...

TTY's are initialized by default (at boot time) with the CLOCAL flag
set. This was originally so that commands like "stty -clocal <
/dev/ttyS1" wouldn't block. (The -F construct is a relatively new one
to stty. It took almost two years for the stty maintainer to integrate
the change and get a new version out. :-)

Note, in the Posix World, applications are supposed to set them to
whatever values they require, and not make assumptions about about the
initial state of the termios flags when a process starts.

                                                - Ted

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