Re: Process target only if prerequisite was processed?

[Noel Yap]

Ian Dunbar wrote:

> > 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.

No, it won't.  Try it out.

It will, however, ignore any existing files named "all" when considering to "build" the 
"all" target.

> 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 $@

This isn't necessary.  Judging from the requirements as given, Ken is 
completely correct.  Try it out.  Then read the docs.

Noel