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From: gwc@root.co.uk (Geoff Clare)
Newsgroups: comp.unix.programmer
Subject: Re: Using select on FIFO's
Message-ID: <2729@root44.co.uk>
Date: 4 Jun 91 12:50:10 GMT
Article-I.D.: root44.2729
References: <BLARSEN.91May30090732@spider.uio.no> <1991May30.165554.4079@chinet.chi.il.us>
Distribution: comp
Organization: UniSoft Ltd., London, England
Lines: 24

les@chinet.chi.il.us (Leslie Mikesell) writes:

> I've always just opened the FIFO with O_RDWR
>on the reader side which (a) doesn't block during the open, and (b)

Although this works on most if not all current UNIX systems, it's not
required by POSIX, so applications using this method may not work
on some future systems.  For maximum portability to current and
future systems, I recommend using the following method to open both
sides of a FIFO to do blocking I/O:

	fd_rd = open("FIFO", O_RDONLY|O_NONBLOCK);
	fd_wr = open("FIFO", O_WRONLY);
	flags = fcntl(fd_rd, F_GETFL);
	fcntl(fd_rd, F_SETFL, flags & ~O_NONBLOCK);

with something like the following tucked away in a header:

#ifndef _POSIX_SOURCE
#define O_NONBLOCK O_NDELAY
#endif
-- 
Geoff Clare <gwc@root.co.uk>  (Dumb American mailers: ...!uunet!root.co.uk!gwc)
UniSoft Limited, London, England.   Tel: +44 71 729 3773   Fax: +44 71 729 3273