Re: Process target only if prerequisite was processed?

[Ian Dunbar]

> > In this case an action needs to be taken if either one of the
> > prerequisites were processed.  The "all" target doesn't generate a file.
> > It just runs a program.
> >
> > --
> > Matt Perry | matt at primefactor dot com
>
> Hi Matt,
>
> If prereq1 and prereq2 are files, then make will already do the right
> thing for you.  Since you say "all" does not generate a file, you should
> declare it phony as follows.
>
> .PHONY: all

Doesn't .PHONY do exactly the opposite of what is wanted here though? .PHONY 
will always cause the "all command" to be processed, when what is wanted (I 
think) is to only do it when one of the prereqs has been processed.

If you change it so that the "all" target actually does create a a file then 
I think it will be closer to what is described.

all: prereq1 prereq2
   @echo "$? was/were updated"
   <some commands you want to run>
   touch $@



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