Reuse percent sign in Makefile prerequesite as subdirectory name

Question

I'd like to learn how to re-use the % sign in my makefile target's prequisite, supposing that the target is X.pdf, and the prerequesite is in X/X.tex.

To elaborate, I currently have a makefile like so:

all: foo.pdf

%.pdf: %.tex
    pdflatex $*.tex

I additionally have a file foo.tex, and when I type make it will make foo.pdf by running pdflatex foo.tex.

Now for various reasons I can't control, my directory structure has changed:

my_dir
|- Makefile
|- foo
   |- foo.tex

I'd like to modify my Makefile such that when it tries to make X.pdf, it looks for the file X/X.tex.

I tried the following (I tried to put '%/%.tex' to tell it to look for foo/foo.tex):

all: foo.pdf

%.pdf: %/%.tex
    pdflatex $*/$*.tex

However, this yields:

No rule to make target `foo.pdf', needed by `all'. Stop.

So does %.pdf: $*/$*.tex.

If I change the %/%.tex to foo/%.tex it works as expected, but I don't want to hard-code the foo in there, because in the future I'll do all: foo.pdf bar.pdf and it should look for foo/foo.tex and bar/bar.tex.

I'm fairly new to Makefiles (experience limited to modifying someone else's to my needs), and have never done a more-than-absolutely basic one, so if anyone could give me a pointer that would help (I don't really know what words to search for in the Makefile documentation - the only ones that looked promising were % and $*, which I couldn't get to work).

Answer 1

you can use VPATH to specify a list of directories that make should search.

exemplary makefile:

# Find all tex files
tex := $(shell find -iname '*.tex')

# Make targets out of them
PDFS := $(notdir $(tex:%.tex=%.pdf))
# specify search folder
VPATH := $(dir $(tex))

all : $(PDFS)

%.pdf : %.tex
        pdflatex $<

or even better would be to use vpath (lowercase):

vpath %.tex $(dir $(tex))

it will look only for .tex files in those directories.