Info Catalog make: Variables Simplify make: Introduction make: Combine By Prerequisite

make: make Deduces

 
 2.5 Letting 'make' Deduce the Recipes
 =====================================
 
 It is not necessary to spell out the recipes for compiling the
 individual C source files, because 'make' can figure them out: it has an
 "implicit rule" for updating a '.o' file from a correspondingly named
 '.c' file using a 'cc -c' command.  For example, it will use the recipe
 'cc -c main.c -o main.o' to compile 'main.c' into 'main.o'.  We can
 therefore omit the recipes from the rules for the object files.  
 Using Implicit Rules Implicit Rules.
 
    When a '.c' file is used automatically in this way, it is also
 automatically added to the list of prerequisites.  We can therefore omit
 the '.c' files from the prerequisites, provided we omit the recipe.
 
    Here is the entire example, with both of these changes, and a
 variable 'objects' as suggested above:
 
      objects = main.o kbd.o command.o display.o \
                insert.o search.o files.o utils.o
 
      edit : $(objects)
              cc -o edit $(objects)
 
      main.o : defs.h
      kbd.o : defs.h command.h
      command.o : defs.h command.h
      display.o : defs.h buffer.h
      insert.o : defs.h buffer.h
      search.o : defs.h buffer.h
      files.o : defs.h buffer.h command.h
      utils.o : defs.h
 
      .PHONY : clean
      clean :
              rm edit $(objects)
 
 This is how we would write the makefile in actual practice.  (The
 complications associated with 'clean' are described elsewhere.  See
 Phony Targets, and Errors in Recipes Errors.)
 
    Because implicit rules are so convenient, they are important.  You
 will see them used frequently.
 

Info Catalog make: Variables Simplify make: Introduction make: Combine By Prerequisite