Which *nix ? BSD : System V

[Guy Harris]

>    If you need to know at compile time whether you're on a Berklix or 
> a System V system, this might help.  It seems to work on all of our
> systems, including the Pyramid split universe wonder:
> 
> 	# include	<fcntl.h>
> 	# ifdef		FNDELAY
> 	# define	BSD
> 	# else
> 	# define	SYS5
> 	# endif
> 
> This assumes that FNDELAY is not defined in the System V fcntl.h, and
> is in the BSD.  Can anyone think of a case where this is not true,

Yes - 4.1BSD.  It would produce an error complaining that <fcntl.h>
couldn't be found.   If you assume that the only UNIXes you're interested
in are 4.2BSD and System III/System V, this will work (no V7, no 4.1BSD).

It also won't work on the OS we're doing for the Power 6/32, if you're really
interested in a strict 4.2/S5 distinction.  It would think you were on
a 4.2 system - we don't have two universes.  However, most 4.2 stuff should
work; our TTY driver, though S5 based, has all the Berkeley features in it
(job control, correct "echoe" handling, "prterase", "crtkill", "ctlecho",
etc., etc.) and has replaced the UNIX/TS 1.0 backward compatible "ioctl"s
with V7/4.2BSD backward compatible "ioctl"s (I've successfully run the
off-the-tape 4.2BSD binaries of "csh" and "vi").

I'm not sure what the result would be with Doug Gwyn's SysV emulation
under 4.2BSD, either; if it doesn't provide a separate copy of <fcntl.h>
your program would be built for 4.2BSD, but would be linked with SysV
libraries.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy