wikipedia ESRI Shapefile

The shapefile format is a popular geospatial vector data format for geographic information system (GIS) software. It is developed and regulated by Esri as a (mostly) open specification for data interoperability among Esri and other GIS software products.[1] The shapefile format can spatially describe vector features: points, lines, and polygons, representing, for example, water wells, rivers, and lakes. Each item usually has attributes that describe it, such as name or temperature.

The shapefile format is a digital vector storage format for storing geometric location and associated attribute information. This format lacks the capacity to store topological information. The shapefile format was introduced with ArcView GIS version 2 in the early 1990s. It is now possible to read and write geographical datasets using the shapefile format with a wide variety of software.

The shapefile format is simple because it can store the primitive geometric data types of points, lines, and polygons. Shapes (points/lines/polygons) together with data attributes can create infinitely many representations about geographic data. Representation provides the ability for powerful and accurate computations.

The term “shapefile” is quite common, but is misleading since the format consists of a collection of files with a common filename prefix, stored in the same directory. The three mandatory files have filename extensions .shp, .shx, and .dbf. The actual shapefile relates specifically to the .shp file, but alone is incomplete for distribution as the other supporting files are required. Legacy GIS software may expect that the filename prefix be limited to eight characters to conform to the DOS 8.3 filename convention, though modern software applications accept files with longer names.

Mandatory files

• .shp — shape format; the feature geometry itself
• .shx — shape index format; a positional index of the feature geometry to allow seeking forwards and backwards quickly
• .dbf — attribute format; columnar attributes for each shape, in dBase IV format

esri.com/library pdf ESRI Shapefile Technicals

GeospatialPython/pyshp library reads and writes ESRI Shapefiles

shp libraries

pyshp

https://pypi.python.org/pypi/pyshp

spatialnetworks/shp-ruby

https://github.com/spatialnetworks/shp-ruby

ruby sqlite

sequel

http://sequel.jeremyevans.net/

ruby georuby

https://github.com/nofxx/georuby