Autoconf is a tool for producing shell scripts that automatically configure software source code packages to adapt to many kinds of UNIX-like systems. The configuration scripts produced by Autoconf are independent of it when they are run.

Together with Automake and Libtool, Autoconf forms the GNU build system.

Autoconf makes use of GNU m4 to transform a user-written 'configure.ac' (formerly, and on older projects, called 'configure.in') file to a portable shell script called 'configure'. The 'configure' script runs non-interactively, and generates customized headers and makefiles derived from pre-written templates. You could say that Autoconf compiles the M4 program in 'configure.ac' into a shell script.

Autoconf was begun in the summer of 1991 by David Mackenzie to support his work at the Free Software Foundation. In the subsequent years it grew to include enhancements from a variety of authors and became the most widely used build configuration system for writing portable free or open source software.

Approach

The Autoconf approach to portability is to test for features, not for versions. For example, the native C compiler on SunOS 4 did not support ISO C. However, it is possible for the user or administrator to have installed an ISO C compliant compiler. A pure version-based approach would not detect the presence of the ISO C compiler, but a feature testing approach would be able to discover the ISO C compiler the user had installed. The rationale of this approach is to gain the following advantages:

• the configure script can get reasonable results on newer or unknown systems
• it allows administrators to customize their machines and have the configure script take advantage of the customizations
• there is no need to keep track of minute details of versions, patch numbers, etc., to figure out whether a particular feature is supported or not

See also

• GNU build system
• pkg-config Detecting package dependencies
• CMake Alternative build system

External links

• GNU Autoconf home page
• GNU Autoconf macro archive
• The Goat Book homepage (aka the Autobook)
• Tutorial " Learning Autoconf and Automake" by Eleftherios Gkioulekas
• Learning the GNU development tools @sourceforge
• Murray Cumming (of gtkmm fame) produced these succinct Autotool info pages: *one *two
• Autotoolset home page
• The " Autotools Tutorial" by Alexandre Duret-Lutz introduces Autoconf, Automake, Libtool, and Gettext.