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<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
<!-- lifted from troff+man by doclifter -->
<refentry>
<refentryinfo><date>14 Aug 2004</date></refentryinfo>
<refmeta>
<refentrytitle>3</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo class='source'>Linux</refmiscinfo>
</refmeta>
<refnamediv id='name'>
<refname>libgps</refname>
<refpurpose>service library for communicationg with the GPS daemon</refpurpose>
</refnamediv>
<refsynopsisdiv id='synopsis'>
<funcsynopsis>
<funcsynopsisinfo>
C:
#include <gps.h>
</funcsynopsisinfo>
<funcprototype>
<funcdef>struct gps_data_t *<function>gps_open</function></funcdef>
<paramdef>char *<parameter>server</parameter></paramdef>
<paramdef>char * <parameter>port</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>gps_query</function></funcdef>
<paramdef>struct gps_data_t *<parameter>gpsdata</parameter></paramdef>
<paramdef>char *<parameter>requests</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>gps_set_raw_hook</function></funcdef>
<paramdef>struct gps_data_t *<parameter>gpsdata</parameter></paramdef>
<paramdef>void (*<parameter>hook</parameter>)(struct gps_data_t *, char *buf)</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>gps_poll</function></funcdef>
<paramdef>struct gps_data_t *<parameter>gpsdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>gps_close</function></funcdef>
<paramdef>struct gps_data_t *<parameter>gpsdata</parameter></paramdef>
</funcprototype>
<funcsynopsisinfo>
Python:
import gps
session = gps.gps(host="localhost", port="2947")
session.set_raw_hook(raw_hook)
session.query(commands)
session.poll()
del session
</funcsynopsisinfo>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id='description'><title>DESCRIPTION</title>
<para><emphasis remap='B'>libgps</emphasis> 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
<citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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
<citerefentry><refentrytitle>libgps</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
<para>Calling <function>gpsd_open()</function> initializes a GPS-data
structure to hold the data collected by the GPS, and returns a socket
attached to
<citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
<function>gpsd_open()</function> returns NULL on errors. errno is
set depending on the error returned from the the socket layer; see
<filename>gps.h</filename> for values and explanations.</para>
<para><function>gpsd_close()</function> ends the session.</para>
<para><function>gpsd_query()</function> 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
<citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
This function returns a 0 on success, or a -1 if there was a
Unix-level read error.</para>
<para><function>gpsd_poll()</function> 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
<function>gpsd_query()</function>, telling the daemon to stream
updates to the client. <function>gpsd_poll()</function> returns the
vakidity mask of the received structure.</para>
<para>Consult <filename>gps.h</filename> to learn more about the data members
and associated timestamps.</para>
<para>The Python implementation supports the same facilities as the C
library. <function>gps_open()</function> 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.</para>
</refsect1>
<refsect1 id='see_also'><title>SEE ALSO</title>
<para>
<citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>xgps</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>libgps</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
</refsect1>
<refsect1 id='author'><title>AUTHOR</title>
<para>Eric S. Raymond <esr@thyrsus.com>.</para>
</refsect1>
</refentry>
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