— Macro: AC_PREREQ (version)

Ensure that a recent enough version of Autoconf is being used. If the version of Autoconf being used to create configure is earlier than version, print an error message to the standard error output and exit with failure (exit status is 63). For example:

          AC_PREREQ([2.62])
     

This macro is the only macro that may be used before AC_INIT, but for consistency, you are invited not to do so.

— Macro: AC_AUTOCONF_VERSION

This macro was introduced in Autoconf 2.62. It identifies the version of Autoconf that is currently parsing the input file, in a format suitable for m4_version_compare (see m4_version_compare); in other words, for this release of Autoconf, its value is `2.62'. One potential use of this macro is for writing conditional fallbacks based on when a feature was added to Autoconf, rather than using AC_PREREQ to require the newer version of Autoconf. However, remember that the Autoconf philosophy favors feature checks over version checks.