get a default value when variable is unset in make

Question

(edit: question more accurate based on @Michael feedback)

In bash, I often use parameter expansion: the following commands print \"default value\" when

Answer 1

If you want to test if a variable has a non-empty value, you can use:

ifeq ($(VARNAME),)
        VARNAME="default value"
else
        do_something_else
endif

For checking if a variable has been defined or not, use ifdef.

Refer to Syntax of Conditionals in the manual for more.