#
# Usage: check_vars VARIABLE...
#
# The function checks if each VARIABLE has non-empty value.  It returns 0
# if all VARIABLEs are non-empty, 1 otherwise.
#
check_vars()
{
	for I in "$@"; do
		if [ "X`eval echo \\$I`" = X ]; then
			log_warn "variable '$I' not defined"
			return 1
		fi
	done

	return 0
}
