Question

I want to check if source file exist, so I assign TO_DIR=/dev/null in my gnu makefile.

APPS=a b c d
install:
  cp $(APPS) $(TO_DIR)

• for normal case, I’ll run ‘TO_DIR=~/bin make install’
• for test case(just make sure file exist for copy), I’ll run ‘TO_DIR=/dev/null make install’

But it will failed, because /dev/null is not a pseudo directory.
Is there better solution?

Answer 1

You could do another make target, like this:

check:
  file $(APPS) > /dev/null

file utility will check the existence of all the files and fail when any of these does not exist. Its output is excessive for this task, so we pipe it to /dev/null

You will run check like this:

make check