libgps.3

很好的一个gps daemon驱动,简单实用

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.TH "3" 3 "14 Aug 2004" "" ""
.SH NAME
libgps \- service library for communicationg with the GPS daemon
.SH "SYNOPSIS"
.ad l
.hy 0



C:

#include <gps\&.h>


.sp
.HP 30
struct\ gps_data_t\ *\fBgps_open\fR\ (char\ *\fIserver\fR, char\ *\ \fIport\fR);
.HP 15
int\ \fBgps_query\fR\ (struct\ gps_data_t\ *\fIgpsdata\fR, char\ *\fIrequests\fR);
.HP 23
void\ \fBgps_set_raw_hook\fR\ (struct\ gps_data_t\ *\fIgpsdata\fR, void\ (*\fIhook\fR)(char\ *buf));
.HP 14
int\ \fBgps_poll\fR\ (struct\ gps_data_t\ *\ \fIgpsdata\fR, void\ *\fIraw_hook\fR(char\ *buf));
.HP 16
void\ \fBgps_close\fR\ (struct\ gps_data_t\ *\fIgpsdata\fR);



Python:

import gps

session = gps\&.gps(host="localhost", port="2947")

session\&.set_raw_hook(raw_hook)

session\&.query(commands)

session\&.poll()

del session


.sp
.ad
.hy

.SH "DESCRIPTION"

.PP
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 \fBgpsd\fR(1) 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 is safe for multiple applications to use simultaneously; it is probably the one you want\&. The low\-level interface is documented at \fBlibgps\fR(3)\&.

.PP
Calling \fBgpsd_open()\fR initializes a GPS\-data structure to hold the data collected by the GPS, and returns a socket attached to \fBgpsd\fR(1)\&. Negative return values indicate errors at the socket layer; see \fIgps\&.h\fR for values and explanations\&.

.PP
\fBgpsd_close()\fR ends the session\&.

.PP
\fBgpsd_query()\fR 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 \fBgpsd\fR(1)\&. This function returns a 1 if any data changed since the last query, a 0 if no data changed, or a \-1 if there was a Unix\-level read error\&.

.PP
\fBgpsd_poll()\fR accepts a one\-line response 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 \fBgpsd_query()\fR, telling the daemon to stream updates to the client\&. If the third argument is non\-NULL, it is used as a hook function to be called on each line of streamed data\&.

.PP
Several member groups within the GPS\-data structure have last\-modified timestamps and change\-flag members associated with them; these get updated on each query or poll as well\&. Consult \fIgps\&.h\fR to learn about the data members and associated timestamps\&.

.PP
The Python implementation supports the same facilities as the C library\&. \fBgps_open()\fR 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\&.

.SH "SEE ALSO"

.PP
 \fBgpsd\fR(1)  \fBlibgps\fR(3) 

.SH "AUTHOR"

.PP
Eric S\&. Raymond <esr@thyrsus\&.com>\&.