13(3)                          GPSD Documentation                          3(3)
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NAME

6       libgpsd - service library for GPS applications
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SYNOPSIS

9       C:
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11       #include <gpsd.h>
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13
14       int gpsd_open_dgps(char * dgpsserver);
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16       void gpsd_init(struct gps_device_t *session, struct * gps_context_t *,
17                      char * device);
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19       int gpsd_activate(struct gps_device_t *session);
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21       void gpsd_deactivate(struct gps_device_t * session);
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23       gps_mask_t gpsd_poll(struct gps_device_t * session);
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25       void gpsd_wrap(struct gps_device_t * session);
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27       void gpsd_report(int d, const char * fmt, ...);
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DESCRIPTION

30       libgpsd is a service library which supports querying GPS devices; link
31       it with the linker option -lgpsd. It is a set of low-level
32       device-handling calls, which gpsd(1) itself uses. See gpsd(3) for a
33       description of the high-level interface, which is almost certainly what
34       you want.
35
36       Calling gpsd_init() initializes a session structure to hold the data
37       collected by the GPS.
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39       The second argument must be a context structure. The library will use
40       it for information that need to be shared between sessions; presently
41       this includes the leap-second correction and possibly a pointer to a
42       shared-memory segment used to communicate with the Network Time
43       Protocol daemon.
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45       After the session structure has been set up, you may modify some of its
46       members.
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48       gpsd_device
49           This member should hold the path name of the device.
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51       baudrate
52           Communication speed in bits per second. For NMEA or SiRF devices,
53           the library automatically hunts through all plausible baud rates,
54           stopping on the one where it sees valid packets. By setting this
55           field you can designate a speed to be tried at the front of the
56           hunt queue
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58       raw_hook
59           A hook function to be executed on each NMEA sentence or as it is
60           read from the GPS. The data from non-NMEA GPSes like the EarthMate
61           will be translated to an NMEA sentence before being passed to the
62           hook. Parameters are a pointer to a gps_data structure full of
63           parsed data, the sentence, and the length of the sentene..
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65       gpsd_activate() initializes the connection to the GPS.
66       gpsd_deactivate() closes the connection. These functions are provided
67       so that long-running programs can release a connection when there is no
68       activity requiring the GPS, and re-acquire it later.
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70       gpsd_poll() queries the GPS and updates the part of the session
71       structure that holds position, speed, GPS signal quality, and other
72       data returned by the GPS. It returns a mask describing which fields
73       have changed.
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75       gpsd_wrap() ends the session, implicitly performing a
76       gpsd_deactivate().
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78       The calling application must define one additional function:
79       gpsd_report(). The library will use this to issue ordinary status
80       messages. Use first argument of 0 for errors, 1 for ordinary status
81       messages, and 2 or higher for debugging messages.
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83       The low-level functions do not allocate or free any dynamic storage.
84       They can thus be used in a long-running application (such as gpsd(8)
85       itself) with a guarantee that they won't cause memory leaks.
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BUGS

88       Writes to the context structure members are not guarded by a mutex.
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SEE ALSO

91       gpsd(8), gps(1), libgps(3).
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AUTHOR

94       Eric S. Raymond <esr@thyrsus.com> based partly on earlier work by Remco
95       Treffkorn, Derrick Brashear, and Russ Nelson.
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99The GPSD Project                  14 Aug 2004                             3(3)