In/Out Modem on the same tty port ?

[Carl S. Gutekunst]

In article <773 at massey.ac.nz> GEustace at massey.ac.nz (Glen Eustace) writes:
>The tty has crw-rw-rw as its rights but when tip tries to access the
>line it gets
>
>/dev/ttyi20: resource busy
>all ports in use
>
>I must be missing something really simple.

Yes. It's called TIOCEXCL. Some process has the tty open (you can use fuser(1M)
to find it), and that process has set the exclusive use flag.

<csg>