OGR2OGR how to update a new column by the length of polyline

Question

Hi I can update new column with area of a polygon object, but don't know, how to update new column in polyline layer with length of polyline.

This works very well for AREA:

for %%f in (*.tab) do (
   ogrinfo %%f -sql "ALTER TABLE %%~nf DROP COLUMN PLO1"
   ogr2ogr %%~nf_new%%~xf %%f -sql "SELECT *, OGR_GEOM_AREA AS PLO1 FROM %%~nf" -f "MapInfo file"
   del %%~nf.* /Q
   ren %%~nf_new.* %%~nf.*
)

How to update Object LENGTH the same way, please?

I can do it in MapInfo:

Update tblnm Set Plo1 = ObjectLen(obj, "m")

But update with OGR would be more usefull for me in this case.

Answer 1

In order to access geometry characteristics in ogr2ogr you should force using SQLite by adding -dialect SQLite. Then the function for obtaing line/linestring length is ST_Length(geometry_field_name)

So try changing the third line of your Area solution into:

ogr2ogr %%~nf_new%%~xf %%f -dialect SQLite -sql "SELECT *, ST_Length(geom) AS PLO1 FROM %%~nf" -f "MapInfo file"

Be sure to pass the right geometry field name to ST_Length function.