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. The only reason this is useful is to prevent a target from getting implicit recipes (from implicit rules or the .DEFAULT special target; see section Using Implicit Rules and see section Defining Last-Resort Default Rules).

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. See section Phony Targets, for a better way to do this.

This document was generated by Davide Tacchella on November 3, 2010 using texi2html 1.82.