Autoconf's main purpose is config.h generation that *just* has #define's right?...

[cs]

I've spent a lot of time reading Autotools docs
and just wanted to verify something before I get
lost in the info overload.....

In general,
the way to write portable and _flexible_ C code is to have
preprocessor directives like:

#ifdef STDIO_H_IS_AVAILABLE
   printf("Hello world.n");
#endif

.... and the way those variables
get defined is to include config.h which is built by configure
script which is built by Autoconf right?

In a nutshell, one should not be intimidated by Autoconf
because it does not do anything more profound or deep
than just make a bunch of #define's right???

...

(The reason this was not obvious is because I read that
one can run arbitrary shell code with Autoconf/configure
system.  This implies Autoconf can do more than I thought
and so I got confused.)

**What else would you use
Autoconf for other than making a list of #defines*?

Thanks,

Chris