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

Running make foo.bak (given that foo.bar exists) yields the following error:

echo "foo"
foo
if [ -d "~/Dropbox" ]; then
/bin/sh: -c: line 1: syntax error: unexpected end of file
make: *** [foo.bak] Error 2

The workaround I made was to have a standalone bash script where the test is implemented and I called the script from the makefile. This, however, sounds very cumbersome. Is there a nicer way to check whether a directory exists from within a makefile?

Answer 1

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