doc/en_US.ISO8859-1/books/fdp-primer/doc-build/chapter.xml

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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:id="doc-build">
  <title>The Documentation Build Process</title>

  <para>This chapter covers organization of the documentation build
    process and how &man.make.1; is used to control it.</para>

  <sect1 xml:id="doc-build-toolset">
    <title>The &os; Documentation Build Toolset</title>

    <para>These are the tools used to build and install the
      <acronym>FDP</acronym> documentation.</para>

    <itemizedlist>
      <listitem>
	<para>The primary build tool is &man.make.1;, specifically
	  <application>Berkeley Make</application>.</para>
      </listitem>

      <listitem>
	<para>Package building is handled by &os;'s
	  &man.pkg.create.1;.</para>
      </listitem>

      <listitem>
	<para>&man.gzip.1; is used to create compressed versions of
	  the document.  &man.bzip2.1; archives are also supported.
	  &man.tar.1; is used for package building.</para>
      </listitem>

      <listitem>
	<para>&man.install.1; is used to install the
	  documentation.</para>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 xml:id="doc-build-makefiles">

    <title>Understanding <filename>Makefile</filename>s in the
      Documentation Tree</title>

    <para>There are three main types of <filename>Makefile</filename>s
      in the &os; Documentation Project tree.</para>

    <itemizedlist>
      <listitem>
	<para><link linkend="sub-make">Subdirectory
	    <filename>Makefile</filename>s</link> simply pass
	  commands to those directories below them.</para>
      </listitem>

      <listitem>
	<para><link linkend="doc-make">Documentation
	    <filename>Makefile</filename>s</link> describe the
	  document(s) that should be produced from this
	  directory.</para>
      </listitem>

      <listitem>
	<para><link linkend="make-includes"><application>Make</application>
	  includes</link> are the glue that perform the document
	  production, and are usually of the form
	  <filename>doc.<replaceable>xxx</replaceable>.mk</filename>.</para>
      </listitem>
    </itemizedlist>

    <sect2 xml:id="sub-make">
      <title>Subdirectory <filename>Makefile</filename>s</title>

      <para>These <filename>Makefile</filename>s usually take the form
	of:</para>

      <programlisting>SUBDIR =articles
SUBDIR+=books

COMPAT_SYMLINK = en

DOC_PREFIX?= ${.CURDIR}/..
.include "${DOC_PREFIX}/share/mk/doc.project.mk"</programlisting>

      <para>The first four non-empty lines define the &man.make.1;
	variables <varname>SUBDIR</varname>,
	<varname>COMPAT_SYMLINK</varname>, and
	<varname>DOC_PREFIX</varname>.</para>

      <para>The <varname>SUBDIR</varname> statement and
	<varname>COMPAT_SYMLINK</varname> statement show how to
	assign a value to a variable, overriding any previous
	value.</para>

      <para>The second <varname>SUBDIR</varname> statement shows how a
	value is appended to the current value of a variable.  The
	<varname>SUBDIR</varname> variable is now <literal>articles
	  books</literal>.</para>

      <para>The <varname>DOC_PREFIX</varname> assignment shows how a
	value is assigned to the variable, but only if it is not
	already defined.  This is useful if
	<varname>DOC_PREFIX</varname> is not where this
	<filename>Makefile</filename> thinks it is - the user can
	override this and provide the correct value.</para>

      <para>What does it all mean?  <varname>SUBDIR</varname>
	mentions which subdirectories below this one the build process
	should pass any work on to.</para>

      <para><varname>COMPAT_SYMLINK</varname> is specific to
	compatibility symlinks (amazingly enough) for languages to
	their official encoding (<filename>doc/en</filename> would
	point to <filename>en_US.ISO-8859-1</filename>).</para>

      <para><varname>DOC_PREFIX</varname> is the path to the root of
	the &os; Document Project tree.  This is not always that easy
	to find, and is also easily overridden, to allow for
	flexibility.  <varname>.CURDIR</varname> is a &man.make.1;
	builtin variable with the path to the current
	directory.</para>

      <para>The final line includes the &os; Documentation Project's
	project-wide &man.make.1; system file
	<filename>doc.project.mk</filename> which is the glue which
	converts these variables into build instructions.</para>
    </sect2>

    <sect2 xml:id="doc-make">
      <title>Documentation <filename>Makefile</filename>s</title>

      <para>These <filename>Makefile</filename>s set &man.make.1;
	variables that describe how to build the documentation
	contained in that directory.</para>

      <para>Here is an example:</para>

      <programlisting>MAINTAINER=nik@FreeBSD.org

DOC?= book

FORMATS?= html-split html

INSTALL_COMPRESSED?= gz
INSTALL_ONLY_COMPRESSED?=

# SGML content
SRCS=  book.xml

DOC_PREFIX?= ${.CURDIR}/../../..

.include "$(DOC_PREFIX)/share/mk/docproj.docbook.mk"</programlisting>

      <para>The <varname>MAINTAINER</varname> variable allows
	committers to claim ownership of a document in the &os;
	Documentation Project, and take responsibility for maintaining
	it.</para>

      <para><varname>DOC</varname> is the name (sans the
	<filename>.xml</filename> extension) of the main document
	created by this directory.  <varname>SRCS</varname> lists all
	the individual files that make up the document.  This should
	also include important files in which a change should result
	in a rebuild.</para>

      <para><varname>FORMATS</varname> indicates the default formats
	that should be built for this document.
	<varname>INSTALL_COMPRESSED</varname> is the default list of
	compression techniques that should be used in the document
	build.  <varname>INSTALL_ONLY_COMPRESS</varname>, empty by
	default, should be non-empty if only compressed documents are
	desired in the build.</para>

      <para>The <varname>DOC_PREFIX</varname> and include statements
	should be familiar already.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="make-includes">
    <title>&os; Documentation Project
      <application>Make</application> Includes</title>

    <para>&man.make.1; includes are best explained by inspection of
      the code.  Here are the system include files:</para>

    <itemizedlist>
      <listitem>
	<para><filename>doc.project.mk</filename> is the main project
	  include file, which includes all the following include
	  files, as necessary.</para>
      </listitem>

      <listitem>
	<para><filename>doc.subdir.mk</filename> handles traversing of
	  the document tree during the build and install
	  processes.</para>
      </listitem>

      <listitem>
	<para><filename>doc.install.mk</filename> provides variables
	  that affect ownership and installation of documents.</para>
      </listitem>

      <listitem>
	<para><filename>doc.docbook.mk</filename> is included if
	  <varname>DOCFORMAT</varname> is <literal>docbook</literal>
	  and <varname>DOC</varname> is set.</para>
      </listitem>
    </itemizedlist>

    <sect2>
      <title><filename>doc.project.mk</filename></title>

      <para>By inspection:</para>

      <programlisting>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"</programlisting>

      <sect3>

	<title>Variables</title>

	<para><varname>DOCFORMAT</varname> and
	  <varname>MAINTAINER</varname> are assigned default values,
	  if these are not set by the document make file.</para>

	<para><varname>PREFIX</varname> is the prefix under which the
	  <link linkend="tools">documentation building tools</link>
	  are installed.  For normal package and port installation,
	  this is <filename>/usr/local</filename>.</para>

	<para><varname>PRI_LANG</varname> should be set to whatever
	  language and encoding is natural amongst users these
	  documents are being built for.  US English is the
	  default.</para>

	<note>
	  <para><varname>PRI_LANG</varname> does not affect which
	    documents can, or even will, be built.  Its main use is
	    creating links to commonly referenced documents into the
	    &os; documentation install root.</para>
	</note>
      </sect3>

      <sect3>
	<title>Conditionals</title>

	<para>The <literal>.if defined(DOC)</literal> line is an
	  example of a &man.make.1; conditional which, like in other
	  programs, defines behavior if some condition is true or if
	  it is false.  <literal>defined</literal> is a function which
	  returns whether the variable given is defined or not.</para>

	<para><literal>.if ${DOCFORMAT} == "docbook"</literal>, next,
	  tests whether the <varname>DOCFORMAT</varname> variable is
	  <literal>"docbook"</literal>, and in this case, includes
	  <filename>doc.docbook.mk</filename>.</para>

	<para>The two <literal>.endif</literal>s close the two above
	  conditionals, marking the end of their application.</para>
      </sect3>
    </sect2>

    <sect2>
      <title><filename>doc.subdir.mk</filename></title>

      <para>This file is too long to explain in detail.  These notes
	describe the most important features.</para>

      <sect3>
	<title>Variables</title>

	<itemizedlist>
	  <listitem>
	    <para><varname>SUBDIR</varname> is a list of
	      subdirectories that the build process should go further
	      down into.</para>
	  </listitem>

	  <listitem>
	    <para><varname>ROOT_SYMLINKS</varname> 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
	      <varname>PRI_LANG</varname>).</para>
	  </listitem>

	  <listitem>
	    <para><varname>COMPAT_SYMLINK</varname> is described in
	      the
	      <link linkend="sub-make">Subdirectory Makefile</link>
	      section.</para>
	  </listitem>
	</itemizedlist>
      </sect3>

      <sect3>
	<title>Targets and Macros</title>

	<para>Dependencies are described by
	  <literal><replaceable>target</replaceable>:
	      <replaceable>dependency1 dependency2
	      ...</replaceable></literal> tuples, where to build
	  <literal>target</literal>, the given
	  dependencies must be built first.</para>

	<para>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.</para>

	<para>A special dependency <literal>.USE</literal> defines
	  the equivalent of a macro.</para>

	<programlisting>_SUBDIRUSE: .USE
.for entry in ${SUBDIR}
	@${ECHO} "===&gt; ${DIRPRFX}${entry}"
	@(cd ${.CURDIR}/${entry} &amp;&amp; \
	${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
.endfor</programlisting>

	<para>In the above, <buildtarget>_SUBDIRUSE</buildtarget> is now
	  a macro which will execute the given commands when it is
	  listed as a dependency.</para>

	<para>What sets this macro apart from other targets?
	  Basically, it is executed <emphasis>after</emphasis> the
	  instructions given in the build procedure it is listed as a
	  dependency to, and it does not adjust
	  <varname>.TARGET</varname>, which is the variable which
	  contains the name of the target currently being
	  built.</para>

	<programlisting>clean: _SUBDIRUSE
	rm -f ${CLEANFILES}</programlisting>

	<para>In the above, <buildtarget>clean</buildtarget> will use
	  the <buildtarget>_SUBDIRUSE</buildtarget> macro after it has
	  executed the instruction
	  <command>rm -f ${CLEANFILES}</command>.  In effect, this
	  causes <buildtarget>clean</buildtarget> to go further and
	  further down the directory tree, deleting built files as it
	  goes <emphasis>down</emphasis>, not on the way back
	  up.</para>

	<sect4>
	  <title>Provided Targets</title>

	  <itemizedlist>
	    <listitem>
	      <para><buildtarget>install</buildtarget> and
		<buildtarget>package</buildtarget> both go down the
		directory tree calling the real versions of themselves
		in the subdirectories
		(<buildtarget>realinstall</buildtarget> and
		<buildtarget>realpackage</buildtarget>
		respectively).</para>
	    </listitem>

	    <listitem>
	      <para><buildtarget>clean</buildtarget> removes files
		created by the build process (and goes down the
		directory tree too).
		<buildtarget>cleandir</buildtarget> does the same, and
		also removes the object directory, if any.</para>
	    </listitem>
	  </itemizedlist>
	</sect4>
      </sect3>

      <sect3>
	<title>More on Conditionals</title>

	<itemizedlist>
	  <listitem>
	    <para><literal>exists</literal> is another condition
	      function which returns true if the given file
	      exists.</para>
	  </listitem>

	  <listitem>
	    <para><literal>empty</literal> returns true if the given
	      variable is empty.</para>
	  </listitem>

	  <listitem>
	    <para><literal>target</literal> returns true if the given
	      target does not already exist.</para>
	  </listitem>
	</itemizedlist>
      </sect3>

      <sect3>
	<title>Looping Constructs in <command>make
	    (.for)</command></title>

	<para><literal>.for</literal> 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.</para>

	<programlisting>_SUBDIRUSE: .USE
.for entry in ${SUBDIR}
	@${ECHO} "===&gt; ${DIRPRFX}${entry}"
	@(cd ${.CURDIR}/${entry} &amp;&amp; \
	${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
.endfor</programlisting>

	<para>In the above, if <varname>SUBDIR</varname> is empty, no
	  action is taken; if it has one or more elements, the
	  instructions between <literal>.for</literal> and
	  <literal>.endfor</literal> would repeat for every element,
	  with <varname>entry</varname> being replaced with the value
	  of the current element.</para>
      </sect3>
    </sect2>
  </sect1>
</chapter>