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Writing Rules
*************

   A "rule" appears in the makefile and says when and how to remake
certain files, called the rule's "targets" (most often only one per
rule).  It lists the other files that are the "dependencies" of the
target, and "commands" to use to create or update the target.

   The order of rules is not significant, except for determining the
"default goal": the target for `make' to consider, if you do not
otherwise specify one.  The default goal is the target of the first
rule in the first makefile.  If the first rule has multiple targets,
only the first target is taken as the default.  There are two
exceptions: a target starting with a period is not a default unless it
contains one or more slashes, `/', as well; and, a target that defines
a pattern rule has no effect on the default goal.  (Pattern Rules)

   Therefore, we usually write the makefile so that the first rule is
the one for compiling the entire program or all the programs described
by the makefile (often with a target called `all').  Goals

* Menu:

* Rule Example                 An example explained.
* Rule Syntax                  General syntax explained.
* Wildcards                    Using wildcard characters such as `*'.
* Directory Search             Searching other directories for source files.
* Phony Targets                Using a target that is not a real file's name.
* Force Targets                You can use a target without commands
                                  or dependencies to mark other
                                  targets as phony.
* Empty Targets                When only the date matters and the
                                  files are empty.
* Special Targets              Targets with special built-in meanings.
* Multiple Targets             When to make use of several targets in a rule.
* Multiple Rules               How to use several rules with the same target.
* Static Pattern               Static pattern rules apply to multiple targets
                                  and can vary the dependencies according to
                                  the target name.
* Double-Colon                 How to use a special kind of rule to allow
                                  several independent rules for one target.
* Automatic Dependencies       How to automatically generate rules giving
                                 dependencies from the source files themselves.