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Writing `'

To produce a `configure' script for a software package, create a file
called `' 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 *Note Existing
Tests::, for their descriptions.  For most other features, you can use
Autoconf template macros to produce custom checks; see *Note Writing
Tests::, for information about them.  For especially tricky or
specialized features, `' might need to contain some
hand-crafted shell commands; see *Note Portable Shell::.  The
`autoscan' program can give you a good start in writing `'
(*note autoscan Invocation::, for more information).
   Previous versions of Autoconf promoted the name `',
which is somewhat ambiguous (the tool needed to process this file is not
described by its extension), and introduces a slight confusion with
`' and so on (for which `.in' means "to be processed by
`configure'").  Using `' is now preferred.