Path: utzoo!mnetor!uunet!hpda!hpcupt1!hpisod2!decot
From: decot@hpisod2.HP.COM (Dave Decot)
Newsgroups: comp.sys.hp
Subject: Re: FIONREAD under HP/UX ioctl
Message-ID: <16710002@hpisod2.HP.COM>
Date: 18 Dec 87 01:19:57 GMT
References: <839@louie.udel.EDU>
Organization: Hewlett Packard, Cupertino
Lines: 32

> Trying to convert this code we have is really starting to look pretty
> dismal.  We seem to have fixed up the AF_UNIX problem with sockets, but
> are now stuck on several ioctl calls.  We need to make a call similar to
> the BSD FIONREAD which returns the number of characters in the input
> buffer of the given file descriptor.  Unfortunately, according to the
> HP/UX docs (in parenthesized fine print at the end of the termio
> section, I might add) this call is not available.  Would anyone know of
> a work-around for this or is it time to punt?
> 
> 					Joel J.  Garrett

FIONREAD is supported in HP-UX on the Series 800.

I assume from your comment that you are using a Series 300.

In this case, you may be able to accomplish your purpose using
the O_NDELAY flag, which is described on open(2) and read(2).

A read() call on a tty file descriptor with O_NDELAY set will
not block if no data is available; it will simply return 0 bytes.

If there is any data available, the read call will read and
return as many bytes as are present or were requested, whichever
is less.  Depending on what the purpose of the ioctl() call you
are porting was, this may be undesirable, tolerable, appropriate,
or even desirable.

See also select(2).

Dave Decot
Hewlett-Packard Company
hpda!decot