4.1 Rule Example
Here is an example of a rule:
foo.o : foo.c defs.h # module for twiddling the frobs
cc -c -g foo.c
Its target is `foo.o' and its prerequisites are `foo.c' and
`defs.h'. It has one command, which is `cc -c -g foo.c'.
The command line starts with a tab to identify it as a command.
This rule says two things:
How to decide whether `foo.o' is out of date: it is out of date
if it does not exist, or if either `foo.c' or `defs.h' is
more recent than it.
How to update the file `foo.o': by running
cc as stated.
The command does not explicitly mention `defs.h', but we presume
that `foo.c' includes it, and that that is why `defs.h' was
added to the prerequisites.