2.7 Rules for Cleaning the Directory
Compiling a program is not the only thing you might want to write rules
for. Makefiles commonly tell how to do a few other things besides
compiling a program: for example, how to 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. We would do this:
| | .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. (See 4.6 Phony Targets, and Errors in Commands.)
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 make the rule run, we have to type `make clean'.
See section How to Run make.
