Shapefile: -update -append -nln WrongNameHere

[peifer]

Below I am re-using the shapefile created for ticket #4357. I am not sure if this is expected behaviour or should there perhaps be a warning, something like: shapefile name and new layer name do not match -- are you sure that you want to create a new shapefile?

$ ogr2ogr -t_srs epsg:3035 ~/tmp/out.shp EBM_A.shp -where "TAA = 4" -update -append -nln WrongNameHere

$ ls -l ~/tmp
-rw-r--r-- 1 peifer mtr     12717 Nov 30 06:16 out.dbf
-rw-r--r-- 1 peifer mtr       369 Nov 30 06:16 out.prj
-rw-r--r-- 1 peifer mtr   1700396 Nov 30 06:16 out.shp
-rw-r--r-- 1 peifer mtr      1716 Nov 30 06:16 out.shx
-rw-r--r-- 1 peifer mtr     24311 Nov 30 06:29 WrongNameHere.dbf
-rw-r--r-- 1 peifer mtr       369 Nov 30 06:29 WrongNameHere.prj
-rw-r--r-- 1 peifer mtr    685040 Nov 30 06:29 WrongNameHere.shp
-rw-r--r-- 1 peifer mtr      3212 Nov 30 06:29 WrongNameHere.shx

[Even Rouault]

Yes I agree this is a weird use case. I had detected that some time ago, and here's the comment I put in the code of the shapefile driver (ogrshapedatasource.cpp, l559)

        /* This is a very weird use case : the user creates/open a datasource */
        /* made of a single shapefile 'foo.shp' and wants to add a new layer */
        /* to it, 'bar'. So we create a new shapefile 'bar.shp' in the same */
        /* directory as 'foo.shp' */
        /* So technically, we will not be any longer a single file */
        /* datasource ... Ahem ahem */

This has existed for a number of past versions, so although suspicious, there are potential users that rely on that behaviour, so I'm tempted to let that as such.

However, you should now that there are now tweaks in ogr2ogr, so that you just remove the -nln argument. ogr2ogr will autodetect that the target datasource is a single layer datasource and automatically append to it layer. So the following should work :

$ ogr2ogr -t_srs epsg:3035 ~/tmp/out.shp EBM_A.shp -where "TAA = 4" -append

Note that I've also removed -update. Since OGR 1.8.0, -append and -overwrite automatically trigger -update.

[peifer]

Thanks for the explanations. Good to know that I can forget about -nln when appending to shapefiles.