Autoconf

Autoconf is a tool for producing configure scripts that adapt software packages to different Unix-like environments. It is part of the GNU build system and aims to simplify portability by generating a single script that checks for system features rather than requiring hand-written tests.

Developers write configure.ac (formerly configure.in) using Autoconf macros such as AC_INIT, AC_CONFIG_HEADERS, and AC_PROG_CC. Autoconf processes these inputs to generate a portable shell script named configure, which performs tests to determine the presence of libraries, headers, compilers, and other environment details.

During execution, the configure script runs various tests and creates outputs such as config.h headers and Makefile fragments. It also supports mechanisms for caching results and for cross-compilation guidance via options like --build, --host, and --target. Packages commonly pair Autoconf with Automake and Libtool to build portable software.

Workflow typically involves writing or updating configure.ac, running autoreconf or autoconf to produce or refresh the configure script, distributing the script, and then having users run ./configure followed by make and make install.

Autoconf was developed as part of the GNU project in the 1990s and is distributed under the GNU General Public License. It remains widely used in open-source projects to automate configuration across diverse platforms.