Which *nix ? BSD : System V

[Arnold Robbins]

...!rtech!daveb suggests checking for BSD or System V by including
<fcntl.h> and then seeing if FNDELAY is or isn't defined.  This probably
works just fine.  I posted a more elaborate solution a couple months
back to net.sources, and will duplicate here (it's short).

Its main advantage is that it differentiates between 4.1, 4.2, and System V
(we have all three around here...)

It is used by saying
CFLAGS=-O `where`
in a makefile
------
#! /bin/sh

# where --- shell file to determine what kind of environment we are in

if test -r /bin/universe	# on a pyramid
then
	OPATH=$PATH
	PATH=/bin
	case `universe` in	# universe is dumb, looking only at argv[0]
	att)	echo "-DUSG -UBSD -UBSD4_2"
		;;

	ucb)	echo "-UUSG -DBSD -DBSD4_2"
		;;

	*)	echo unknown operating system! 1>&2
		echo "-UUSG -UBSD -UBSD4_2"	# undefine them all
		;;
	esac
	PATH=$OPATH
else		# on something that is not a pyrmaid
	if grep SIGTSTP /usr/include/signal.h > /dev/null
	then		# berkeley unix
		if test -r /usr/include/whoami.h	# 4.1
		then
			echo "-UUSG -DBSD -UBSD4_2"
		else					# 4.2
			echo "-UUSG -DBSD -DBSD4_2"
		fi
	else			# ATT unix
		echo "-DUSG -UBSD -UBSD4_2"
	fi
fi
-- 
Arnold Robbins
CSNET:	arnold at gatech	ARPA:	arnold%gatech.csnet at csnet-relay.arpa
UUCP:	{ akgua, allegra, hplabs, ihnp4, seismo, ut-sally }!gatech!arnold

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