linux bash stty bug

[Yi Yan]

  Probles description:

     I tried to send data from Linux /dev/ttyS0 to a SCO unix serial
port.   The two serial ports are connected with a NULL MODEM.
If XON/XOFF flow control is used, I set the linux /dev/ttyS0 with:

     ( stty 9600 ixon ixoff -crtscts cs8 ;
        while : ; do sleep 3600 ; done ) < /dev/ttyS0 &

and set the SCO serial port same way. Now I can send data by

      echo "some data" > /dev/ttyS0

There is no trouble at all.  But if I use Hardware flow control,
the case is different.

   First I set up the linux terminal as:

     ( stty 9600 crtscts -ixon -ixoff -ixany ;
        while : ; do sleep 3600 ; done ) < /dev/ttyS0 &

The SCO serial port is set as Hardware flow control same way.
If I use :

       echo "some data" > /dev/ttyS0

It will send nothing and the command never return.

Later I wrote a c program to send the data.  The C code works only if
the port is opened as:

    int fd = open("/dev/ttyS0", O_RDWR | O_NONBLOCK );

If the O_NONBLOCK micro is not there, the c code does not send
any data either.

   I am not sure where is the bug: in the tty driver, in the shell, or need 
another flag in the stty command ?


   Yi Yan





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