Makefile and rm -f file.{ext1,ext2,ext3} issue

Question

Hello,

Could you explain me, why Makefile rule:

clean:
    rm -f foo.{bar1,bar2,bar3}

does not result in removing files: foo.bar1 foo.bar2 and foo.bar3? I believe I saw pattern like that many times in various Makefiles, but I'm currently writing my own Makefile and can't make that rule work correctly (no files are removed).

I'm using:

• gnu make 3.81
• gnu bash 4.1.5

Bash evals that pattern as I suspect:

$ echo test.{a,b,c}
test.a test.b test.c

Thanks!

UPDATE

Thank to David's hint I found solution for the problem described above. The gnu make uses the /bin/sh by default and that is why a.{1,2,3} isn't evaluated to a.1 a.2 a.3.

To make 'make' use bash instead of sh add following line to your Makefile:

SHELL=/bin/bash

from now a.{1,2,3} will be considered as a.1 a.2 a.3

Answer 1

Is there a file named clean in the directory? If so, make will consider that target up to date and won't run the corresponding command. To fix that, add this line to your makefile:

.PHONY: clean

If when you run make clean you get the output

make: `clean' is up to date.

then that's probably your problem.

Answer 2

It's because the shell isn't being invoked here, but rather rm is directly. Since the shell does the {} substitution, what rm 'sees' is the raw foo.{bar1,bar2,bar3} string. As there's no such file, nothing happens.

You should use one of GNUmake's string macros to have it perform the expansion for you.