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Re: Presence-only dependencies?
From: |
Paul D. Smith |
Subject: |
Re: Presence-only dependencies? |
Date: |
Fri, 21 Oct 2005 17:00:48 -0400 |
%% 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.
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