3.1 Writing `configure.ac'

To produce a configure script for a software package, create a file called `configure.ac' that contains invocations of the Autoconf macros that test the system features your package needs or can use. Autoconf macros already exist to check for many features; see 5. Existing Tests, for their descriptions. For most other features, you can use Autoconf template macros to produce custom checks; see 6. Writing Tests, for information about them. For especially tricky or specialized features, `configure.ac' might need to contain some hand-crafted shell commands; see 10. Portable Shell Programming. The autoscan program can give you a good start in writing `configure.ac' (see section 3.2 Using autoscan to Create `configure.ac', for more information).

Previous versions of Autoconf promoted the name `configure.in', which is somewhat ambiguous (the tool needed to produce this file is not described by its extension), and introduces a slight confusion with `config.h.in' and so on (for which `.in' means "to be processed by configure"). Using `configure.ac' is now preferred.

3.1.1 A Shell Script Compiler		Autoconf as solution of a problem
3.1.2 The Autoconf Language		Programming in Autoconf
3.1.3 Standard `configure.ac' Layout		Standard organization of configure.ac