On 11/19/2011 11:40 AM, Ari Jolma wrote:
On 11/18/2011 09:02 PM, Even Rouault wrote:
Le vendredi 18 novembre 2011 15:04:55, Ari Jolma a écrit :
Hi,

A few days ago on this list I mentioned that the following works using a
recent version from trunk (and Perl bindings):

use Geo::GDAL;
$datasource = Geo::OGR::Open('/home/ajolma/data/parks.shp');
Geo::OGR::Driver('GML')->Copy($datasource, '/dev/stdout');

I'm testing a simple WFS written in Perl and basically the above is the
contents of the GetFeature subroutine (the datasource name comes of
course from a configuration file). However, using this in a Perl CGI
program leads to "RuntimeError Failed to create GML file /dev/stdout." -
it seems like the VSI does not work when the Perl program is run as a
CGI program. I may investigate the issue more but maybe somebody has an
answer right away. - I can forward the output to a file and then send
the file but it would be nice to feed it directly to the client.
The most obvious idea I have is that something closes the stdout of the forked
CGI ?

The standard way to send text (HTML, XML, ..) to the client in a Perl CGI process is to print to stdout (exactly the same way as one does in a command line Perl program). Thus it seems that the VSI stdout is somehow not a standard stdout - I'll take a deeper look into what goes on.

I found the problem. It is changeset 23022 (by you, Even :), which removes support for "stdout" and adds "/dev/stdout" as an alias to "/vsistdout/". Simple, but took me a while to find out especially as the log message begins "mentions in the doc".


Another thing is that in mod_perl sending to client is through a handle (use the print method of an object) - it would be nice to be able to give that handle to the GDAL copy method.

mod_perl is probably not a problem. However, Perl supports memory files too and it would be interesting to be able to use VSI memory files and Perl memory files interchangeably.

Ari


Ari



Regards,

Ari

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