The Shortest configure.ac File
The simplest possible configure.ac file has just two lines, as shown in Example 3-1.
Example 3-1. The simplest configure.ac file
AC_INIT([Jupiter], [1.0]) AC_OUTPUT
To those new to Autoconf, these two lines appear to be a couple of function calls, perhaps in the syntax of some obscure programming language. Don't let their appearance throw you—these are M4 macro calls. The macros are defined in files distributed with the autoconf package. You can find the definition of
AC_INIT, for example, in the autoconf/general.m4 file in Autoconf's installation directory (usually /usr/(local/)share/autoconf).
AC_OUTPUT is defined in autoconf/status.m4.