[GRASS-user] result from g.copy when layer exists

[Rainer M Krug]

Nikos Alexandris <nik at nikosalexandris.net> writes:

> Rainer MK wrote:
>> >> I am a bit irritated,  ut maybe I don't dee the reasoning behind this:'
>
>> >> ,----
>> >> | RASS 7.0.svn (grass):~ > g.copy rast=MASK,tmp
>> >> | WARNING: <tmp> already exists
>> >> | [Raster MASK present]
>> >> | GRASS 7.0.svn (grass):~ >
>> >> `----
>
>> >> If the layer already exists, shouldn't the command give actually an
>> >> error and not only a warning?
>
>> >> A warning implies for me that the command worked, but maybe something
>> >> unexpected could have happened (or happened) - but this one clearly did
>> >> not work, as the layer has not been copied?
>
> Glynn Clements:
>> > In GRASS, errors are fatal; the program will be terminated as soon as
>> > the error message has been printed.
>
> Rainer MK:
>> Exactly - if e.g. in r.mapcalc an invalid expression is entered,
>> r.mapcalc issues the error message and quits.
>  
>> > Each of g.copy's options accept an arbitray number of
>> > source+destination pairs, and the various options aren't mutually
>> > exclusive (e.g. a single invocation can copy both raster and vector
>> > maps).
>
>> True.
>
>> > If it can't perform a particular copy for any reason, it generates a
>> > warning then moves on to the next item.
>
>> True - but this does not answer my question. But I looked at cp in bash,
>> and it behaves in the same way.
>> So I think I have to live with this.
>
> Just sharing my thoughts about: Imagine copying 1000 maps.  And one is meant 
> to fail, say the 1st one of them.  You wouldn't, probably, like the copy 
> process to be interrupted just for one map that failed. Right?

Depends: when using in a script, I would like it to fail, as the
following commands might give wrong resuls as they would be based on the
previous map and not the copied one.

Also, in a script this could mean that previous commands did not clean
their temporary files properly - other cause for an interruption of the
script.

When doing it from the command prompt, I would say: just tell me which
ones failed - correct.

SO the best would be a flag which says "error on map exists".

Cheers,

Rainer
 
>
> Greets, Nikos


-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

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