File: make.info,  Node: Introduction,  Next: Makefiles,  Prev: Overview,  Up: Top

2 An Introduction to Makefiles
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You need a file called a "makefile" to tell 'make' what to do.  Most
often, the makefile tells 'make' how to compile and link a program.

   In this chapter, we will discuss a simple makefile that describes how
to compile and link a text editor which consists of eight C source files
and three header files.  The makefile can also tell 'make' how to run
miscellaneous commands when explicitly asked (for example, to remove
certain files as a clean-up operation).  To see a more complex example
of a makefile, see *note Complex Makefile::.

   When 'make' recompiles the editor, each changed C source file must be
recompiled.  If a header file has changed, each C source file that
includes the header file must be recompiled to be safe.  Each
compilation produces an object file corresponding to the source file.
Finally, if any source file has been recompiled, all the object files,
whether newly made or saved from previous compilations, must be linked
together to produce the new executable editor.

* Menu:

* Rule Introduction::           What a rule looks like.
* Simple Makefile::             A simple makefile.
* How Make Works::              How 'make' processes this makefile.
* Variables Simplify::          Variables make makefiles simpler.
* make Deduces::                Letting 'make' deduce the recipes.
* Combine By Prerequisite::     Another style of makefile.
* Cleanup::                     Rules for cleaning the directory.