Re: bidirectional communication

[Petr M. <mi...@ph...>]

> > Well, ad to the above problem with fifo in Octave -- why the following in
> > bash does not work?
> >
> > bash$ mkfifo cau
> > bash$ tail -f cau
> >
> > and in another xterm:
> >
> > gnuplot> set print "cau"
> > gnuplot> print "hello"
> >
> > Only sometimes the text appears in the "tail", but always it gets flushed
> > after "set print" (closing print file) or quitting gnuplot -- and why it
> > works in the C demo without closing "set print"?
>
> This may well be a problem of buffering.  FIFOs are fully buffered by
> default, I think, whereas stderr, the default 'set print' output channel,
> is always completely unbuffered by C standard requirements.  I.e. it
> should help to explicitly setbuf() the channel 'set print' opened to
> unbuffered.

I've tried to put
   setvbuf(print_out, (char *) NULL, _IONBF, 0);
into print_command(), but it does not help either.

Also, when restarting gnuplot for the 2nd time and go to print to "cau",
then tail -f will not show the new text any longer.

---
Petr Mikulik