Hello world with Autotools

The Autotools are de facto standard for building C/C++ code in the Linux world. It is a very flexible build system, but because of its flexibility it has a quite steep learning curve. Here is the bare minimum example that will get you started.

The bare minimum

To build a simple hello world program with Autotools you just need 3 files. Here is the file structure:

bare-minimum-example
├── Makefile.am
├── configure.ac
└── main.c

The configure will be created from configure.ac.

#configure.ac
AC_INIT([hello-world], 1.0)
AM_INIT_AUTOMAKE([foreign])

AC_PROG_CC
AC_CONFIG_FILES([Makefile])

AC_OUTPUT

And a Makefile.am to generate a Makefile.in from which the final Makefile will be created.

#Makefile.am
bin_PROGRAMS = hello
hello_SOURCES = hello.c

Contents of hello.c:

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

int main(int argc, char **argv)
{
    printf("Hello world!\n");
    return 0;
}

Building

First you need to transform your configure.ac into a configure script. This is done by the autoconf. The configure script uses a Makefile.in to produce the final Makefile. The Makefile.in is usually generated by the automake from a Makefile.am. Are you still with me?

configure.ac -> |autoconf| ->  configure  -> |           |
                                             |./configure| -> Makefile
 Makefile.am -> |automake| -> Makefile.in -> |           |

You can use autoreconf to run autoconf and automake for you.

$ autoreconf -vfi

Then you can run the produced ./configure script and build you application.

$ ./configure
$ make
$ ./hello
Hello world!

And that’s pretty much it.

Next steps

This example is everything you need to know in order to build a simple program with Autotools . If your scenario is more complex, then with the help of the official documentation you will be able extend it.