Re: using the date relationship of two older files as a prerequisite

[Brian J. Murrell]

On 12-12-04 11:04 AM, Cook, Malcolm wrote:
> Brian - try this:
> 
> # Path to this current makefile
> MAKEFILE=$(lastword $(MAKEFILE_LIST))
> 
> # constructed path to a subdirectory to hold datestamp files
> DATESTAMP=$(MAKEFILE).d/datestamp
> 
> # rule to create datestamp files, copying the files date
> $(DATESTAMP)/%:  %
>       mkdir -p $(@D) ; \
>       touch -r $* $@
> 
> T: O $(DATESTAMP)/O 
>       cat O > T

This does not appear to work.  Given the three files:

-rw-rw-r-- 1 brian brian 0 Dec  3 13:00 Makefile.d/datestamp/O
-rw-rw-r-- 1 brian brian 0 Dec  5 16:06 O
-rw-rw-r-- 1 brian brian 0 Dec  7 09:25 T

Which were created from a previous run where only O existed and after
touching O to make it newer than the Makefile.d/datestamp/O (but older
than T, as I had previously stated could/would be the case).

$ make -d -f Makefile
...
Updating goal targets....
Considering target file `T'.
  Considering target file `O'.
...
  No need to remake target `O'.
  Considering target file `Makefile.d/datestamp/O'.
   Looking for an implicit rule for `Makefile.d/datestamp/O'.
   Trying pattern rule with stem `O'.
   Trying implicit prerequisite `O'.
   Found an implicit rule for `Makefile.d/datestamp/O'.
    Pruning file `O'.
   Finished prerequisites of target file `Makefile.d/datestamp/O'.
   Prerequisite `O' is newer than target `Makefile.d/datestamp/O'.
  Must remake target `Makefile.d/datestamp/O'.
mkdir -p Makefile.d/datestamp ; \
        touch -r O Makefile.d/datestamp/O
Putting child 0x08aa2090 (Makefile.d/datestamp/O) PID 29521 on the chain.
Live child 0x08aa2090 (Makefile.d/datestamp/O) PID 29521
Reaping winning child 0x08aa2090 PID 29521
Removing child 0x08aa2090 PID 29521 from chain.
  Successfully remade target file `Makefile.d/datestamp/O'.
 Finished prerequisites of target file `T'.
 Prerequisite `O' is older than target `T'.
 Prerequisite `Makefile.d/datestamp/O' is newer than target `T'.
No need to remake target `T'.

And indeed:

$ ls -l O Makefile.d/datestamp/O T
-rw-rw-r-- 1 brian brian 0 Dec  5 16:06 Makefile.d/datestamp/O
-rw-rw-r-- 1 brian brian 0 Dec  5 16:06 O
-rw-rw-r-- 1 brian brian 0 Dec  7 09:25 T

Makefile.d/datestamp/O was updated to O's timestamp but T was not
updated since it was not re-made.

Cheers and thanks much for your time and consideration.  I do appreciate
it.  Sorry it took me a bit to get back to it.

b.

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