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

There is a very different answer that allows you to use your if statements as you envisioned them in one shell:

.ONESHELL:
foo.bak: foo.bar
    echo "foo"
    if [ -d "~/Dropbox" ]; then
        echo "Dir exists"
    fi

Note that the only difference is the ONESHELL special target.

Answer 2

This approach functions with minimal echos:

.PHONY: all
all:
ifneq ($(wildcard ~/Dropbox/.*),)
        @echo "Found ~/Dropbox."
else
        @echo "Did not find ~/Dropbox."
endif

Answer 3

Make commands, if a shell command, must be in one line, or be on multiple lines using a backslash for line extension. So, this approach will work:

foo.bak: foo.bar
    echo "foo"
    if [ -d "~/Dropbox" ]; then echo "Dir exists"; fi

Or

foo.bak: foo.bar
    echo "foo"
    if [ -d "~/Dropbox" ]; then \
        echo "Dir exists"; \
    fi

Answer 4

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.)

Answer 5

I use the following to detect if a file or a directory exists and act upon it :

$(if $(filter expected,$(wildcard *)), the expected file exists)

With your request :

.PHONY: ~/Dropbox

~/Dropbox:
    echo "Dir exists"

foo.bak: foo.bar | $(if $(filter ~/Dropbox,$(wildcard ~/*)), the expected file exists)

Which can further be simplify :

foo.bak: foo.bar | $(wildcard ~/Dropbox)

Answer 6

Try this:

.PHONY: all
something:
    echo "hi"
all:
    test -d "Documents" && something

This will execute the commands under something only if Documents exists.

In order to address the problem noted in the comments, you can make a variable like this:

PATH_TEST = ~/SomeDirectory

test -d $(PATH_TEST) && something