SUBDIRS=c

all:
	@for i in $(SUBDIRS); \
	do \
		if [ ! -d $$i ]; \
		then \
			echo Error: $$i not a directory; \
			exit 1; \
		fi; \
		cd $$i; \
		if make $@; \
		then \
			echo > /dev/null; \
		else \
			exit 1; \
			fi; \
		cd ..; \
	done

clean:
	@for i in $(SUBDIRS); \
	do \
		if [ ! -d $$i ]; \
		then \
			echo Error: $$i not a directory; \
			exit 1; \
		fi; \
		cd $$i; \
		if make $@; \
		then \
			echo > /dev/null; \
		else \
			exit 1; \
			fi; \
		cd ..; \
	done