[gdal-dev] Selecting OGR Driver Based on File Name

[Frank Warmerdam]

Joel Odom wrote:
> Is there a canonical way to pick an OGR driver based on a file name or 
> on a generalized connect string?  (For example, if the file name ends in 
> ".shp", it would select the Shapefile driver.)  Thanks.

Joel,

No.

I really wanted to send this out with just that one word answer, but I
can't help myself but elaborate.

First, I think file format identification based on filename extension is
a terrible idea, and I curse those operating systems that try to build it
into the graphical shell.   Likewise a pox on applications that carry on
this tradition.

Second, there are a number of OGR file formats that have no dependency on
extension.  For example GML, DGN, DXF, PCIDSK.  For these formats any
extension is fine and only letting people pick a file if it has some
particular is offensive to me.

Third, there are lots of database connection formats that aren't extension
based.  Typically these can be identified based on a prefix string like
MYSQL: though not always.

Despite my feelings on this matter, on the GDAL side of the house we actually
provide a metadata item on drivers allowing specification of a preferred
extension which applications can use.  We also have an "identify" mechanism
that will try to efficiently identify what format a file or dataset name
string is without necessarily actually opening it.

Unfortunately, the OGR world is less sophisticated in this regard and lacks
these two mechanisms.  This is one reason I'd like to have a "grand
unification" of GDAL and OGR one day.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent