Multi tool use

make clean: Only remove files that have been generated

With the Makefile I'm working on, I convert pdf files into txt files.

Makefile

I've implemented a clean target that would remove all .txt files. However, I do not wish to delete the source files, only those that have been generated.

clean

Example:
I have following files in my folder:

pdfsource.pdf and donotharm.txt

pdfsource.pdf

donotharm.txt

Running my makefile would create following file:

pdfsource.txt

pdfsource.txt

For now, my clean looks like this:

clean

rm -f *.txt


Using make clean would not only delete pdfsource.txt, which is desired, but also donotharm.txt.

make clean

pdfsource.txt

donotharm.txt

I think I could use: .PRECIOUS: donotharm.txt, but this is really specific. I'd like to have a general solution to this.

.PRECIOUS: donotharm.txt

Thanks in advance!

.PRECIOUS

rm -f *.txt

rm

.PRECIOUS

make

clean

.PRECIOUS

2 Answers
2

You can list the generated files in a make variable and use it to clean only these:

PDF := $(wildcard *.pdf)
TEXT := $(patsubst %.pdf,%.txt,$(PDF))
...
clean:
rm -f $(TEXT)


Or, if you prefer a more compact (but a bit less readable) form:

clean:
rm -f $(patsubst %.pdf,%.txt,$(wildcard *.pdf))


Of course, this works only if there is no {foo.pdf,foo.txt} pair for which you want to preserve foo.txt from deletion by make clean.

{foo.pdf,foo.txt}

foo.txt

make clean

Note: using make variables, in such a case, is usually a good idea because they can be shared among various rules. Example:

PDF := $(wildcard *.pdf)
TEXT := $(patsubst %.pdf,%.txt,$(PDF))

.PHONY: all clean

all: $(TEXT)

$(TEXT): %.txt: %.pdf
pdftotext $< $@

clean:
rm -f $(TEXT)


Another approach: "make -nps" gives you all make's metadata about dependencies. For any intermediate file, it prints

filename: ...


So you can exactly delete such files with a generic "clean" rule:

clean:; MAKEFLAGS= ${MAKE} -j1 -spinf $(word 1,${MAKEFILE_LIST})
| sed -n '/^# I/,$${/^[^#[%.][^ %]*: /s/:.*//p;}; 1s|.*|${clean}|p' | xargs rm -rf


The first line handles use of makefiles other than the defaults (makefile, GNUmakefile, Makefile)
In the "sed" command:

/^# I/,$


... selects the zone of make metadata with dependencies.

/^[^#[%.][^ %]*: /


... filters out comments, implicit rules, and files with no dependencies (the trailing space). It doesn't filter out phony targets; oh well.
Finally:

1s|.*|${clean}|p


adds any explicit targets for "clean" -- what you know that make does not; e.g.

clean += tmpdir/* *.gcda


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