get shapefile metadata
$ orginfo -al shapefile.shp
$ ogr2ogr \
-f GeoJSON \
-where "STATE = 'CA'" \
-s_srs crs:84 \
-t_srs crs:84 \
output.geojson \
input.shp
$ ogr2ogr \
-f GeoJSON \
-where "STATEFP10 = '06'" \
-s_srs crs:84 \
-t_srs crs:84 \
zip.geojson \
tl_2010_06_zcta510.shp
$ ogr2ogr \
-f GeoJSON \
-s_srs crs:84 \
-t_srs crs:84 \
state.geojson \
tl_2010_06_state10.sh
$ topojson \
-p statefp=STATEFP \
-p name=NAME \
-o output.topojson \
input.geojson
$ topojson \
-p zipcode=ZCTA5CE10 \
-o zip.topojson \
zip.geojson
combine multiple files
$ topojson \
-o foo.topojson \
-p zipcode=ZCTA5CE10 \
tl_2010_06_zcta510/zip.geojson \
tl_2010_06_state10/state.geojson
$ topojson \
-o uk.json \
--id-property SU_A3 \
--properties name=NAME \
-- \
subunits.geojson \
places.geojson