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5.8 Defining Canned Recipes
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When the same sequence of commands is useful in making various targets,
you can define it as a canned sequence with the 'define' directive, and
refer to the canned sequence from the recipes for those targets.  The
canned sequence is actually a variable, so the name must not conflict
with other variable names.

   Here is an example of defining a canned recipe:

     define run-yacc =
     yacc $(firstword $^)
     mv y.tab.c $@
     endef

Here 'run-yacc' is the name of the variable being defined; 'endef' marks
the end of the definition; the lines in between are the commands.  The
'define' directive does not expand variable references and function
calls in the canned sequence; the '$' characters, parentheses, variable
names, and so on, all become part of the value of the variable you are
defining.  *Note Defining Multi-Line Variables: Multi-Line, for a
complete explanation of 'define'.

   The first command in this example runs Yacc on the first prerequisite
of whichever rule uses the canned sequence.  The output file from Yacc
is always named 'y.tab.c'.  The second command moves the output to the
rule's target file name.

   To use the canned sequence, substitute the variable into the recipe
of a rule.  You can substitute it like any other variable (*note Basics
of Variable References: Reference.).  Because variables defined by
'define' are recursively expanded variables, all the variable references
you wrote inside the 'define' are expanded now.  For example:

     foo.c : foo.y
             $(run-yacc)

'foo.y' will be substituted for the variable '$^' when it occurs in
'run-yacc''s value, and 'foo.c' for '$@'.

   This is a realistic example, but this particular one is not needed in
practice because 'make' has an implicit rule to figure out these
commands based on the file names involved (*note Using Implicit Rules:
Implicit Rules.).

   In recipe execution, each line of a canned sequence is treated just
as if the line appeared on its own in the rule, preceded by a tab.  In
particular, 'make' invokes a separate sub-shell for each line.  You can
use the special prefix characters that affect command lines ('@', '-',
and '+') on each line of a canned sequence.  *Note Writing Recipes in
Rules: Recipes.  For example, using this canned sequence:

     define frobnicate =
     @echo "frobnicating target $@"
     frob-step-1 $< -o $@-step-1
     frob-step-2 $@-step-1 -o $@
     endef

'make' will not echo the first line, the 'echo' command.  But it _will_
echo the following two recipe lines.

   On the other hand, prefix characters on the recipe line that refers
to a canned sequence apply to every line in the sequence.  So the rule:

     frob.out: frob.in
             @$(frobnicate)

does not echo _any_ recipe lines.  (*Note Recipe Echoing: Echoing, for a
full explanation of '@'.)