14 Aug 2004 3 3 Linux libgps service library for communicationg with the GPS daemon C: #include <gps.h> struct gps_data_t *gps_open char *server char * port int gps_query struct gps_data_t *gpsdata char *requests void gps_set_raw_hook struct gps_data_t *gpsdata void (*hook)(struct gps_data_t *, char *buf) int gps_poll struct gps_data_t *gpsdata void gps_close struct gps_data_t *gpsdata Python: import gps session = gps.gps(host="localhost", port="2947") session.set_raw_hook(raw_hook) session.query(commands) session.poll() del session libgps is a service library which supports querying GPS devices; link it with the linker option -lgps. There are two interfaces supported in it; one high-level interface that goes through gpsd1 and is intended for concurrent use by several applications, and one low-level interface that speaks directly with the serial or USB device to which the GPS is attached. This page describes the high-level interface that is safe for multiple applications to use simultaneously; it is probably the one you want. The low-level interface is documented at libgps3. Calling gpsd_open() initializes a GPS-data structure to hold the data collected by the GPS, and returns a socket attached to gpsd1. gpsd_open() returns NULL on errors. errno is set depending on the error returned from the the socket layer; see gps.h for values and explanations. gpsd_close() ends the session. gpsd_query() queries the daemon, accepts a one-line response, and updates parts of the GPS-data structure that correspond to data changed since the last call. The second argument must be a string containing letters from the command set documented at gpsd1. This function returns a 0 on success, or a -1 if there was a Unix-level read error. gpsd_poll() accepts a response, or sequence of responses, from the daemon and interprets it as though it were a query response (the return value is as for a query). It is meant to be used after the user has issued an 'R' or 'W' command with gpsd_query(), telling the daemon to stream updates to the client. gpsd_poll() returns the vakidity mask of the received structure. Consult gps.h to learn more about the data members and associated timestamps. The Python implementation supports the same facilities as the C library. gps_open() is replaced by the initialization of a gps session object; the other calls are methods of that object. Resources within the session object will be properly released when it is garbage-collected. gpsd8, xgps1, libgps3. Eric S. Raymond <esr@thyrsus.com>.