This is best explained by inspection of the code. Here are the system include files:
doc.project.mk is the main project
include file, which includes all the following include files, as
necessary.
doc.subdir.mk handles traversing of
the document tree during the build and install processes.
doc.install.mk provides variables
that affect ownership and installation of documents.
doc.docbook.mk is included if
DOCFORMAT is docbook
and DOC is set.
By inspection:
DOCFORMAT?= docbook
MAINTAINER?= doc@FreeBSD.org
PREFIX?= /usr/local
PRI_LANG?= en_US.ISO8859-1
.if defined(DOC)
.if ${DOCFORMAT} == "docbook"
.include "doc.docbook.mk"
.endif
.endif
.include "doc.subdir.mk"
.include "doc.install.mk"DOCFORMAT and MAINTAINER
are assigned default values, if these are not set by the
document make file.
PREFIX is the prefix under which the
documentation building tools are
installed. For normal package and port installation, this is
/usr/local.
PRI_LANG should be set to whatever
language and encoding is natural amongst users these documents are
being built for. US English is the default.
PRI_LANG in no way affects what documents
can, or even will, be built. Its main use is creating links to
commonly referenced documents into the FreeBSD documentation
install root.
The .if defined(DOC) line is an example of
a make conditional which, like in
other programs, defines behavior if some condition is true or
if it is false. defined is a function which
returns whether the variable given is defined or not.
.if ${DOCFORMAT} == "docbook", next,
tests whether the DOCFORMAT variable is
"docbook", and in this case, includes
doc.docbook.mk.
The two .endifs close the two above
conditionals, marking the end of their application.
This is too long to explain by inspection, you should be able to work it out with the knowledge gained from the previous chapters, and a little help given here.
SUBDIR is a list of subdirectories
that the build process should go further down
into.
ROOT_SYMLINKS is the name of
directories that should be linked to the document
install root from their actual locations, if the current
language is the primary language (specified by
PRI_LANG).
COMPAT_SYMLINK is described in the
Subdirectory Makefile
section.
Dependencies are described by
target:
dependency1 dependency2 ...
tuples, where to build target, you need to build
the given dependencies first.
After that descriptive tuple, instructions on how to build the target may be given, if the conversion process between the target and its dependencies are not previously defined, or if this particular conversion is not the same as the default conversion method.
A special dependency .USE defines
the equivalent of a macro.
_SUBDIRUSE: .USE
.for entry in ${SUBDIR}
@${ECHO} "===> ${DIRPRFX}${entry}"
@(cd ${.CURDIR}/${entry} && \
${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
.endforIn the above, _SUBDIRUSE is now a
macro which will execute the given commands when it is listed
as a dependency.
What sets this macro apart from other targets? Basically,
it is executed after the instructions
given in the build procedure it is listed as a dependency to,
and it does not adjust .TARGET, which is the
variable which contains the name of the target currently
being built.
clean: _SUBDIRUSE
rm -f ${CLEANFILES}In the above, clean will use the
_SUBDIRUSE macro after it has
executed the instruction
rm -f ${CLEANFILES}. In effect, this causes
clean to go further and further down
the directory tree, deleting built files as it goes
down, not on the way back up.
install and
package both go down the
directory tree calling the real versions of themselves
in the subdirectories
(realinstall and
realpackage
respectively).
clean removes files created
by the build process (and goes down the directory tree
too). cleandir does the same,
and also removes the object directory, if any.
exists is another condition
function which returns true if the given file exists.
empty returns true if the given
variable is empty.
target returns true if the given
target does not already exist.
.for provides a way to repeat a set of
instructions for each space-separated element in a variable.
It does this by assigning a variable to contain the current
element in the list being examined.
_SUBDIRUSE: .USE
.for entry in ${SUBDIR}
@${ECHO} "===> ${DIRPRFX}${entry}"
@(cd ${.CURDIR}/${entry} && \
${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
.endforIn the above, if SUBDIR is empty, no
action is taken; if it has one or more elements, the
instructions between .for and
.endfor would repeat for every element,
with entry being replaced with the value of
the current element.
All FreeBSD documents are available for download at http://ftp.FreeBSD.org/pub/FreeBSD/doc/
Questions that are not answered by the
documentation may be
sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.