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Rules
for cleaning the directory
Compiling
a program is not the only thing for which you might want to write rules.
Makefiles commonly tells how to do a few other things besides compiling
a program; for instance, how to delete all the object files and executables
so that the directory is clean. The following shows how to write a make
rule for cleaning the example editor.
clean:
rm edit $(objects)
In practice, you might want
to write the rule in a somewhat more complicated manner to handle unanticipated
situations. Use input like the following example.
.PHONY : clean
clean :
-rm edit $(objects)
This prevents make
from using an actual file called clean
allowing it to continue in spite of errors from rm.
(See Phony targets
and in Errors
in commands.) A rule such as this should not be placed at the
beginning of the makefile, since you do not want it to run by default!
Thus, in the example makefile, you want the rule for edit
which recompiles the editor, to remain the default goal. Since clean
is not a dependency 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, use make
clean. See How
to run make.
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