[gnu.bash.bug] parameter substitution

andy@CSVAX.CALTECH.EDU (Andy Fyfe) (06/14/89)

Given
	X=
	echo ${X:-abcd}
bash will echo "", while /bin/sh (sun, 3b1) and /bin/ksh (3b1) will
echo "abcd".  The man pages talk about varibles being "set and non-null"
or "not set or null".