What are Makefile.am and Makefile.in?

Question

These two files are mostly seen in open source projects.

What are they for, and how do they work?

Answer 1

Simple example

Shamelessly adapted from: http://www.gnu.org/software/automake/manual/html_node/Creating-amhello.html and tested on Ubuntu 14.04 Automake 1.14.1.

Makefile.am

SUBDIRS = src
dist_doc_DATA = README.md

README.md

Some doc.

configure.ac

AC_INIT([automake_hello_world], [1.0], [bug-automake@gnu.org])
AM_INIT_AUTOMAKE([-Wall -Werror foreign])
AC_PROG_CC
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([
 Makefile
 src/Makefile
])
AC_OUTPUT

src/Makefile.am

bin_PROGRAMS = autotools_hello_world
autotools_hello_world_SOURCES = main.c

src/main.c

#include 
#include 

int main (void) {
  puts ("Hello world from " PACKAGE_STRING);
  return 0;
}

Usage

autoreconf --install
mkdir build
cd build
../configure
make
sudo make install
autoconf_hello_world
sudo make uninstall

This outputs:

Hello world from automake_hello_world 1.0

Notes

• autoreconf --install generates several template files which should be tracked by Git, including Makefile.in. It only needs to be run the first time.

• make install installs:

  • the binary to /usr/local/bin
  • README.md to /usr/local/share/doc/automake_hello_world

On GitHub for you to try it out.