Test whether a directory exists inside a makefile

Question

In his answer @Grundlefleck explains how to check whether a directory exists or not. I tried some to use this inside a makefile as follow:

foo.b         


        

Answer 1

I had a case where I wanted to define a variable based on the test whether a directory exists or not at the top-most level of the Makefile where the approaches described above don't work. I found here a nice solution which can be used like this:

MY_DIRNAME=../External
ifneq "$(wildcard $(MY_DIRNAME) )" ""
  # if directory MY_DIRNAME exists:
  INCLUDES += -I../External
else
  # if it doesn't:
  INCLUDES += -I$(HOME)/Code/External
endif

This will modify the variable INCLUDES based on whether the directory stored in MY_DIRNAME exists or not.

(Motivation: In my case this variable would be used in another Makefile included later by the first:

include $(SFRAME_DIR)/Makefile.common

I wanted to have the same Makefile work in two different environments in a simple way.)