CODEWITHSUNDEEP
makefile
Rob Gilliam
Rob Gilliam

Reputation: 2950

Can make build targets for unknown pre-requisites?

I need to process all files with a particular extension, and package up the results into a single archive. Is there a way to have make do this?

For example suppose I need to take all the .w files and produce a .n file for each one with any vowels turned to periods, then tar up the results. If I create a Makefile as follows:

novowels.tar: %.n
    tar cf $@ $^

%.n: %.w
    sed -e "s/[aeiou]/./g" > $@ < $<

make (unsurprisingly) returns the following if there are no .n files in the directory:

make: *** No rule to make target '%.n', needed by 'novowels.tar'.  Stop.

I can call make the.n and it'll create the file from the.w (assuming that exists), and if I then call make it'll get included in the archive.

The question is: how (best) to have make realise that there are a whole load of .w files that need converting to .n files in the first place?

Upvotes: 1

Views: 44

Answers (1)

Klaus
Klaus

Reputation: 25613

Take this as an example:

ALLFILES_IN  := $(wildcard *.w)
ALLFILES_OUT := $(ALLFILES_IN:.w=.n)


$(info In : $(ALLFILES_IN))
$(info Out: $(ALLFILES_OUT))

%.n: %.w 
   cat $< > $@

all.tar: $(ALLFILES_OUT)
  @echo "Tar:" $^

Maybe you find something like that helpful:

CPP_FILES := $(wildcard src/*.cpp)
OBJ_FILES := $(addprefix obj/,$(notdir $(CPP_FILES:.cpp=.o)))

which was stolen from: Can I compile all .cpp files in src/ to .o's in obj/, then link to binary in ./?

Upvotes: 3

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