Info Catalog make: Canned Recipes make: Recipes

make: Empty Recipes

 
 5.9 Using Empty Recipes
 =======================
 
 It is sometimes useful to define recipes which do nothing.  This is done
 simply by giving a recipe that consists of nothing but whitespace.  For
 example:
 
      target: ;
 
 defines an empty recipe for 'target'.  You could also use a line
 beginning with a recipe prefix character to define an empty recipe, but
 this would be confusing because such a line looks empty.
 
    You may be wondering why you would want to define a recipe that does
 nothing.  One reason this is useful is to prevent a target from getting
 implicit recipes (from implicit rules or the '.DEFAULT' special target;
DONTPRINTYET  Implicit Rules and *noteDefining Last-Resort Default Rules:
DONTPRINTYET  Implicit Rules and Defining Last-Resort Default Rules

 Last Resort.).
 
    Empty recipes can also be used to avoid errors for targets that will
 be created as a side-effect of another recipe: if the target does not
 exist the empty recipe ensures that 'make' won't complain that it
 doesn't know how to build the target, and 'make' will assume the target
 is out of date.
 
    You may be inclined to define empty recipes for targets that are not
 actual files, but only exist so that their prerequisites can be remade.
 However, this is not the best way to do that, because the prerequisites
 may not be remade properly if the target file actually does exist.
 Phony Targets Phony Targets, for a better way to do this.
 

Info Catalog make: Canned Recipes make: Recipes