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====== Programming - Make - Basic Make Example ======

===== Basic Example =====

==== Create a C program ====

<file c hello.c>
#include <stdio.h>

int main()
{
  printf("Hello World");
  return 0;
}
</file>

----

==== Create a Makefile ====

<file bash Makefile>
hello: hello.c
</file>

----

==== Run Make ====

<code bash>
make
</code>

returns:

<code bash>
cc     hello.c   -o hello
</code>

<WRAP info>
**NOTE:**  This compiles the C program.

Most distributions will have cc pointing to the default C compiler.
</WRAP>

----

==== Run Make Again ====

<code bash>
make
</code>

returns:

<code bash>
make: 'hello' is up to date.
</code>

<WRAP info>
**NOTE:**  As nothing has changed, there is no need for Make to recompile the C program.

To have the program be recompiled:

  * Run **touch hello.c**, or
  * Delete the compiled program, **rm hello**, or
  * Modify the C program and run make again.

</WRAP>

----

===== Enhanced Make =====

Use variables within the Makefile:

<file bash Makefile>
CC=gcc
CFLAGS=-g
hello : hello.c
</file>

returns:

<code bash>
gcc -g    hello.c   -o hello
</code>

----

===== Add further options to the Makefile =====

<code bash>
CC=gcc
CFLAGS=-g
# Comment next line to turn off optimization
CFLAGS+=-O
hello : hello.c
</code>

<WRAP info>
**NOTE:**  The implicit rule being used is:

<code bash>
$(CC) $(CFLAGS) $(CPPFLAGS) hello.c -o hello
</code>
</WRAP>

----

===== Use an object =====

Besides compiling, the Makefile can also link the object files:

<file bash Makefile>
hello : hello.o mylib.o
hello.o : hello.c hello.h mylib.h
mylib.o : mylib.c mylib.h
</file>

<WRAP info>
**NOTE:**  Thanks to the default rules, this is all that is needed by Make.

The make program is smart enough to see that it needs hello.o, it will go find the rule for hello.o and so on.

Of course, additional lines can be added to control further what happens for the build process.
</WRAP>