Previous: Splitting Lines, Up: Command Syntax

5.1.2 Using Variables in Commands

The other way in which make processes commands 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 This occurs after make has finished reading all the makefiles and the target is determined to be out of date; so, the commands for targets which are not rebuilt are never expanded.

Variable and function references in commands 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 command, 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
             for i in $(LIST); do \
                 echo $$i; \

results in the following command being passed to the shell:

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

which generates the expected result: