.PHONY: all
all:	tst_b.o tst_a.o

Makefile:: ;

tst_b.o tst_a.o: tst_a.h tst_b.h

#.SECONDARY: tst_a.c tst_b.c

%.o: %.c
	@echo 'C: *=$* @=$@ <=$<'
	sleep .5
	@for i in $^; do test -f "$$i" || echo "Missing: $$i"; done
	@for i in $^; do test -s "$$i" || echo "Empty: $$i"; done

%.c %.h: %.a
	@echo 'A: *=$* @=$@ <=$<'
	rm -f $*.[ch]
	touch $*.c $*.h
	sleep 1
	echo "$*.c ($<)" >$*.c
	sleep 1
	echo "$*.h ($<)" >$*.h

%.c %.h: %.b
	@echo 'B: *=$* @=$@ <=$<'
	rm -f $*.[ch]
	touch $*.c $*.h
	sleep 1
	echo "$*.c ($<)" >$*.c
	sleep 1
	echo "$*.h ($<)" >$*.h