如何在Makefile配方中实现for循环

Question

Although the below script, is intended find a makefile in the sub directory level of 1 and make them recursively, I'm not able to find any success with it.

for file in `find $(pwd)/ -maxdepth 2 -mindepth 2 -type f -name 'Makefile'`; do\
    make --directory=$(dirname $file);\
done

What might be the problem here?

Answer 1

In this recipe you do not intend $(pwd) , $(dirname ...) and $file to be expanded by make , but they are are, because you have not escaped $ . (Strictly, you do not intend the $f in $file to be expanded by make ). Re-write as:

for file in `find $$(pwd)/ -maxdepth 2 -mindepth 2 -type f -name 'Makefile'`; do\
    make --directory=$$(dirname $$file);\
done

Later

Is there a better and simple way of making sub modules of a project?

Yes. The canonical way would be like:

# Identify the sub-directories some way, not necessarily like this:
SUBDIRS := $(dir $(shell find $$(pwd)/ -maxdepth 2 -mindepth 2 -type f -name 'Makefile'))

.PHONY: $(SUBDIRS)

all: $(SUBDIRS)
# Maybe some recipe...

$(SUBDIRS):
    $(MAKE) -C $@