5.6 Recursive Use of make
Recursive use of make means using make as a command in a
makefile. This technique is useful when you want separate makefiles for
various subsystems that compose a larger system. For example, suppose you
have a subdirectory `subdir' which has its own makefile, and you would
like the containing directory's makefile to run make on the
subdirectory. You can do it by writing this:
| | subsystem:
cd subdir && $(MAKE)
|
or, equivalently, this (see section Summary of Options):
| | subsystem:
$(MAKE) -C subdir
|
You can write recursive make commands just by copying this example,
but there are many things to know about how they work and why, and about
how the sub-make relates to the top-level make. You may
also find it useful to declare targets that invoke recursive
make commands as `.PHONY' (for more discussion on when
this is useful, see 4.6 Phony Targets).
For your convenience, GNU make sets the variable CURDIR to
the pathname of the current working directory for you. If -C is
in effect, it will contain the path of the new directory, not the
original. The value has the same precedence it would have if it were
set in the makefile (by default, an environment variable CURDIR
will not override this value). Note that setting this variable has no
effect on the operation of make
