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Re: Presence-only dependencies?


From: Matthew Sanderson
Subject: Re: Presence-only dependencies?
Date: Mon, 24 Oct 2005 09:59:06 +1000 (EST)

<slaps forehead> D'oh! I remember that feature now, but it didn't occur to
me to use it like that. Thanks, Paul.

--matthew

Matthew Sanderson
Senior Programmer (UNIX)
TCG Information Systems Pty Ltd
Sydney, Australia
address@hidden
http://www.formtrap.com/
+61 (02) 8303 2407

On Fri, 21 Oct 2005, Paul D. Smith wrote:

> %% Matthew Sanderson <address@hidden> writes:
>
>   ms> To be precise: I am defining a presence-only dependency of A on B
>   ms> to mean that A depends only on the presence of a file named B; B's
>   ms> last-mod-time is not taken into account. A will not be
>   ms> re-generated if B is newer; but if B is missing, a seperate
>   ms> (normal) rule may re-generate it, and if so, then afterwards the
>   ms> presence-only dependency rule will cause A to also be re-generated
>   ms> from the just-created B.
>
> I think you can do this with current capabilities, like this:
>
>     A: $(if $(wildcard B),,B)
>
> which will result in "A: B" if B does _NOT_ exist, or just "A:" (with no
> prerequisite) if B _DOES_ exist.
>
> --
> -------------------------------------------------------------------------------
>  Paul D. Smith <address@hidden>          Find some GNU make tips at:
>  http://www.gnu.org                      http://make.paulandlesley.org
>  "Please remain calm...I may be mad, but I am a professional." --Mad Scientist
>




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