Linux autoreconf Command with Practical Examples

Introduction

In this lab, we will explore the purpose and usage of the autoreconf command in Linux. The autoreconf command is a tool used to automatically generate the necessary build system files, such as configure scripts and Makefiles, for software projects that use the GNU Autotools build system. This includes tools like autoconf, automake, and libtool, which help to create a standardized build process for software projects, making it easier to compile and install the software on different platforms. We will prepare the development environment and apply the autoreconf command to a sample project, demonstrating its practical usage and benefits.

Linux Commands Cheat Sheet

Skills Graph

Understand the Purpose of autoreconf Command

In this step, we will explore the purpose of the autoreconf command in Linux. The autoreconf command is a tool used to automatically generate the necessary build system files for a software project, such as configure scripts and Makefiles.

The autoreconf command is typically used in projects that use the GNU Autotools build system, which includes tools like autoconf, automake, and libtool. These tools help to create a standardized build process for software projects, making it easier to compile and install the software on different platforms.

Let's start by creating a sample project directory:

mkdir -p ~/project/sample-project
cd ~/project/sample-project

Example output:

labex@ubuntu:~/project/sample-project$

Now, let's create a simple configure.ac file in the project directory:

nano configure.ac

Add the following content to the configure.ac file:

AC_INIT([Sample Project], [1.0], [[email protected]])
AM_INIT_AUTOMAKE
AC_PROG_CC
AC_OUTPUT

Save and close the file.

The configure.ac file is the main input file for the autoconf tool, which generates the configure script. The AM_INIT_AUTOMAKE macro initializes the automake tool, which generates the Makefiles.

Now, let's run the autoreconf command to generate the necessary build system files:

autoreconf -i

Example output:

labex@ubuntu:~/project/sample-project$ autoreconf -i
libtoolize: Putting files in AC_CONFIG_MACRO_DIRS, 'M4'.
libtoolize: Consider adding 'AC_CONFIG_MACRO_DIRS([m4])' to configure.ac and
libtoolize: rerunning libtoolize, to keep the correct libtool macros in-tree.
configure.ac:1: installing './compile'
configure.ac:1: installing './config.guess'
configure.ac:1: installing './config.sub'
configure.ac:1: installing './install-sh'
configure.ac:1: installing './ltmain.sh'
configure.ac:1: installing './missing'

The autoreconf command scans the project directory, identifies the necessary build system files, and generates them automatically. This saves developers from having to manually create and maintain these files, which can be a time-consuming and error-prone process.

After running autoreconf, you should see the following files in your project directory:

$ ls -l
total 32
-rw-rw-r-- 1 labex labex  210 Apr 12 15:32 aclocal.m4
-rw-rw-r-- 1 labex labex  279 Apr 12 15:32 compile
-rw-rw-r-- 1 labex labex 1076 Apr 12 15:32 config.guess
-rw-rw-r-- 1 labex labex  554 Apr 12 15:32 config.sub
-rw-rw-r-- 1 labex labex 3328 Apr 12 15:32 configure
-rw-rw-r-- 1 labex labex 2925 Apr 12 15:32 configure.ac
-rw-rw-r-- 1 labex labex  700 Apr 12 15:32 install-sh
-rw-rw-r-- 1 labex labex 8632 Apr 12 15:32 ltmain.sh
-rw-rw-r-- 1 labex labex  554 Apr 12 15:32 missing

These files are the necessary build system files that the autoreconf command has generated based on the configure.ac file.

Prepare the Development Environment for autoreconf

In this step, we will prepare the development environment for using the autoreconf command. We will install the necessary build tools and dependencies required for the GNU Autotools build system.

First, let's update the package lists and install the required packages:

sudo apt-get update
sudo apt-get install -y autoconf automake libtool

Example output:

Hit:1 http://archive.ubuntu.com/ubuntu jammy InRelease
Get:2 http://security.ubuntu.com/ubuntu jammy-security InRelease [110 kB]
Get:3 http://archive.ubuntu.com/ubuntu jammy-updates InRelease [114 kB]
...
Selecting previously unselected package autoconf.
Preparing to unpack .../autoconf_2.71-2_all.deb ...
Unpacking autoconf (2.71-2) ...
Selecting previously unselected package automake.
Preparing to unpack .../automake_1.16.5-1.3_all.deb ...
Unpacking automake (1.16.5-1.3) ...
Selecting previously unselected package libtool.
Preparing to unpack .../libtool_2.4.6-15.2ubuntu1_amd64.deb ...
Unpacking libtool (2.4.6-15.2ubuntu1) ...
Setting up autoconf (2.71-2) ...
Setting up automake (1.16.5-1.3) ...
Setting up libtool (2.4.6-15.2ubuntu1) ...
Processing triggers for man-db (2.10.2-1) ...

The autoconf, automake, and libtool packages are the core components of the GNU Autotools build system. These tools work together to generate the necessary build system files, such as configure scripts and Makefiles, for a software project.

Now, let's verify that the packages were installed correctly:

which autoconf
which automake
which libtool

Example output:

/usr/bin/autoconf
/usr/bin/automake
/usr/bin/libtool

The output shows that the required packages have been installed and are available in the system's PATH.

With the development environment set up, we're now ready to use the autoreconf command in the next step.

Apply autoreconf to a Sample Project

In this step, we will apply the autoreconf command to a sample project and observe the generated build system files.

Let's start by creating a new sample project directory:

mkdir -p ~/project/sample-project-2
cd ~/project/sample-project-2

Example output:

labex@ubuntu:~/project/sample-project-2$

Now, let's create a simple configure.ac file in the project directory:

nano configure.ac

Add the following content to the configure.ac file:

AC_INIT([Sample Project 2], [1.0], [[email protected]])
AM_INIT_AUTOMAKE
AC_PROG_CC
AC_OUTPUT

Save and close the file.

Next, let's run the autoreconf command to generate the necessary build system files:

autoreconf -i

Example output:

labex@ubuntu:~/project/sample-project-2$ autoreconf -i
libtoolize: Putting files in AC_CONFIG_MACRO_DIRS, 'M4'.
libtoolize: Consider adding 'AC_CONFIG_MACRO_DIRS([m4])' to configure.ac and
libtoolize: rerunning libtoolize, to keep the correct libtool macros in-tree.
configure.ac:1: installing './compile'
configure.ac:1: installing './config.guess'
configure.ac:1: installing './config.sub'
configure.ac:1: installing './install-sh'
configure.ac:1: installing './ltmain.sh'
configure.ac:1: installing './missing'

After running autoreconf, let's take a look at the generated files:

ls -l

Example output:

total 32
-rw-rw-r-- 1 labex labex  210 Apr 12 15:41 aclocal.m4
-rw-rw-r-- 1 labex labex  279 Apr 12 15:41 compile
-rw-rw-r-- 1 labex labex 1076 Apr 12 15:41 config.guess
-rw-rw-r-- 1 labex labex  554 Apr 12 15:41 config.sub
-rw-rw-r-- 1 labex labex 3328 Apr 12 15:41 configure
-rw-rw-r-- 1 labex labex 2925 Apr 12 15:41 configure.ac
-rw-rw-r-- 1 labex labex  700 Apr 12 15:41 install-sh
-rw-rw-r-- 1 labex labex 8632 Apr 12 15:41 ltmain.sh
-rw-rw-r-- 1 labex labex  554 Apr 12 15:41 missing

You can see that the autoreconf command has generated the same set of build system files as in the previous step, including the configure script and other supporting files.

These generated files can now be used to compile and install the software project using the standard GNU Autotools build process.

Summary

In this lab, we explored the purpose of the autoreconf command in Linux, which is used to automatically generate the necessary build system files for a software project, such as configure scripts and Makefiles. We created a sample project directory, set up a basic configure.ac file, and then ran the autoreconf command to generate the required build system files. This process is essential for projects that use the GNU Autotools build system, as it helps to create a standardized build process that can be used across different platforms.

Linux Commands Cheat Sheet