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'\" t
.\" Title: 3
.\" Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\" Date: 14 Aug 2004
.\" Manual: GPSD Documentation
.\" Source: The GPSD Project
.\" Language: English
.\"
.TH "3" "3" "14 Aug 2004" "The GPSD Project" "GPSD Documentation"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
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.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
libgpsd \- service library for GPS applications
.SH "SYNOPSIS"
.sp
.ft B
.nf
C:
#include <gpsd\&.h>
.fi
.ft
.HP \w'int\ gpsd_open_dgps('u
.BI "int gpsd_open_dgps(char\ *\ " "dgpsserver" ");"
.HP \w'void\ gpsd_init('u
.BI "void gpsd_init(struct\ gps_device_t\ *" "session" ", struct\ *\ " "gps_context_t\ *" ", char\ *\ " "device" ");"
.HP \w'int\ gpsd_activate('u
.BI "int gpsd_activate(struct\ gps_device_t\ *" "session" ");"
.HP \w'void\ gpsd_deactivate('u
.BI "void gpsd_deactivate(struct\ gps_device_t\ *\ " "session" ");"
.HP \w'gps_mask_t\ gpsd_poll('u
.BI "gps_mask_t gpsd_poll(struct\ gps_device_t\ *\ " "session" ");"
.HP \w'void\ gpsd_wrap('u
.BI "void gpsd_wrap(struct\ gps_device_t\ *\ " "session" ");"
.SH "DESCRIPTION"
.PP
\fBlibgpsd\fR
is a service library which supports querying GPS devices; link it with the linker option \-lgpsd\&. It is a set of low\-level device\-handling calls, which
\fBgpsd\fR(1)
itself uses\&. See
\fBgpsd\fR(3)
for a description of the high\-level interface, which is almost certainly what you want\&.
.PP
Calling
\fBgpsd_init()\fR
initializes a session structure to hold the data collected by the GPS\&.
.PP
The second argument must be a context structure\&. The library will use it for information that need to be shared between sessions; presently this includes the leap\-second correction and possibly a pointer to a shared\-memory segment used to communicate with the Network Time Protocol daemon\&.
.PP
After the session structure has been set up, you may modify some of its members\&.
.PP
\fIgpsd_device\fR
.RS 4
This member should hold the path name of the device\&.
.RE
.PP
\fIbaudrate\fR
.RS 4
Communication speed in bits per second\&. For NMEA or SiRF devices, the library automatically hunts through all plausible baud rates, stopping on the one where it sees valid packets\&. By setting this field you can designate a speed to be tried at the front of the hunt queue
.RE
.PP
\fBgpsd_activate()\fR
initializes the connection to the GPS\&.
\fBgpsd_deactivate()\fR
closes the connection\&. These functions are provided so that long\-running programs can release a connection when there is no activity requiring the GPS, and re\-acquire it later\&.
.PP
\fBgpsd_poll()\fR
queries the GPS and updates the part of the session structure that holds position, speed, GPS signal quality, and other data returned by the GPS\&. It returns a mask describing which fields have changed\&.
.PP
\fBgpsd_wrap()\fR
ends the session, implicitly performing a
\fBgpsd_deactivate()\fR\&.
.PP
The calling application must define one additional function:
\fBgpsd_report()\fR\&. The library will use this to issue ordinary status messages\&. See
gpsd\&.h
in the source distribution for the set of logging levels\&.
.PP
The low\-level functions do not allocate or free any dynamic storage\&. They can thus be used in a long\-running application (such as
\fBgpsd\fR(8)
itself) with a guarantee that they won\*(Aqt cause memory leaks\&.
.SH "BUGS"
.PP
Writes to the context structure members are not guarded by a mutex\&.
.SH "SEE ALSO"
.PP
\fBgpsd\fR(8),
\fBgps\fR(1),
\fBlibgps\fR(3)\&.
.SH "AUTHOR"
.PP
Eric S\&. Raymond <esr@thyrsus\&.com> based partly on earlier work by Remco Treffkorn, Derrick Brashear, and Russ Nelson\&.
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