Using Variables in Recipes

The other way in which make processes recipes is by expanding any variable references in them (see Basics of Variable References). This occurs after make has finished reading all the makefiles and the target is determined to be out of date; so, the recipes for targets which are not rebuilt are never expanded.

Variable and function references in recipes have identical syntax and semantics to references elsewhere in the makefile. They also have the same quoting rules: if you want a dollar sign to appear in your recipe, you must double it (‘$$’). For shells like the default shell, that use dollar signs to introduce variables, it’s important to keep clear in your mind whether the variable you want to reference is a make variable (use a single dollar sign) or a shell variable (use two dollar signs). For example:

LIST = one two three
all:
        for i in $(LIST); do \
            echo $$i; \
        done

results in the following command being passed to the shell:

for i in one two three; do \
    echo $i; \
done

which generates the expected result:

one
two
three