Node:Rules for cleaning the directory, Previous:Combining rules by prerequisite, Up:Writing a makefile

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Rules for cleaning the directory

Compiling a program is not the only thing you might want to write rules for. Makefiles commonly do a few other things besides compiling a program: for example, they can often delete all the object files and executables so that the directory is clean.

Here is how we could write a make rule for cleaning our example editor:

clean:
        rm edit $(objects)

In practice, we might want to write the rule in a somewhat more complicated manner to handle unanticipated situations. For example:

.PHONY : clean
clean :
        -rm edit $(objects)

This prevents make from getting confused by an actual file called clean and causes it to continue in spite of errors from rm.

A rule such as this should not be placed at the beginning of the makefile, because we do not want it to run by default! Thus, in the example makefile, we want the rule for edit, which recompiles the editor, to remain the default goal.

Since clean is not a prerequisite of edit, this rule will not run at all if we give the command make with no arguments. In order to run the rule, we have to type make clean.