On Nov 23, 2010, at 04:03, Rob van der Heij wrote:
> On Tue, Nov 23, 2010 at 11:42 AM, Paul Gilmartin <[email protected]> wrote:
>> First, I'm restricted to minidisks; my sysprog is stuck
>> somewhere in the Twentieth Century. But I'd like to be
>> able to delete an output file if the input file doesn't
>> exist. So:
>
> Use the "disk" stage rather than the "<" if your input file is optional.
>
> The 'nose stage' verifies that your input file exists before raising
> the commit level (and possibly doing irreversable things). In most
> cases you don't want to wipe out files because of a missing input
> file. Your case may be different.
>
Thanks. "commit" isn't really in my vocabulary. I don't think it
existed when I first brushed against Pipelines, perhaps before SFS
was a consideration.
I might want to do things like:
pipe disk FN1 FT1 A | locate NONEXISTENT | sort
| xlate | ... | > FN2 FT2 A
What stages must I beware of that might not raise the commit level
until an input record is available? (What should I look for in the
documentation?) I'd be most comfortable if I could put something
just before the 'tail stage' that forced the commit level and passed
its input stream unmodified, or unconditionally force commit in '>'.
Thanks again,
gil
