Convert Shapefile to CSV file
ogr2ogr -f "CSV" output.csv input.shp -lco GEOMETRY=AS_XY
Convert Shapefile to GeoJSON
ogr2ogr -f "GeoJSON" output.json input.shp
Extract geometries from Shapefile with Attribute iso_a2 = 'GB'
ogr2ogr -where "iso_a2 = 'GB'" gb.shp input.shp
Previous two commands combined in a single command
ogr2ogr -f GeoJSON -where "iso_a2 = 'GB'" gb.json input.shp