Reading and writing of "ESRI shapefile" format spatial data. Only the three vector types (points, lines, and polygons) can be stored in shapefiles.
A shapefile should consist of at least four files: .shp (the geometry), .dbf (the attributes), .shx (the index that links the two, and .prj (the coordinate reference system). If the .prj file is missing, a warning is given. If any other file is missing an error occurs (although one could in principle recover the .shx from the .shp file). Additional files are ignored.