[LCP]stat'ing a FIFO

[Robert Wuest]

Steve,

I knew that! :) Or I should have known that. Or I did once upon a time.

Thank you very much!

Robert

Steve Baker wrote:
> 
> Robert Wuest <rwuest at wuest.org> wrote:
> > Can anyone tell me how to stat a FIFO?  In a program 1, I pipe() twice,
> > then fork. In the child, I dup() the appropiate fd's to stdin and
> > stdout, and exec program 2.  Normal stuff.  In either program:
> >
> >       struct stat stat_buf;
> >       fstat( fd, &stat_buf );  // fd = 0 or 1 in program 2's case
> >
> > always has 0 for the size, stat_buf.st_size.  Even when I know there is
> > unread data in there.  Read or write. Is there some other trick I need
> > to know?
> 
>   I believe what you're looking for is the FIONREAD ioctl(), thus:
> 
>   int n;
> ...
>   ioctl(fd,FIONREAD,&n);
> 
>   /*
>    * n now contains the number of bytes available for reading on the
>    * descriptor fd.
>    */
> 
> > Also, is there anyway to get a signal when there is data to be read?
> 
>   SIGIO is supposed to be for that, but I've never used it, and don't know if
> it even works.  I think it might be limited to tty I/O events.
> 
>                                                                 - Steve