gpsd/man/gpsfake.xml

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<!DOCTYPE refentry PUBLIC
   "-//OASIS//DTD DocBook XML V4.1.2//EN"
   "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
<refentry id='gpsfake.1'>
<refentryinfo><date>30 March 2020</date></refentryinfo>
<refmeta>
<refentrytitle>gpsfake</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo class="source">The GPSD Project</refmiscinfo>
<refmiscinfo class="manual">GPSD Documentation</refmiscinfo>
</refmeta>
<refnamediv id='name'>
<refname>gpsfake</refname>
<refpurpose>test harness for gpsd, simulating a GPS</refpurpose>
</refnamediv>
<refsynopsisdiv id='synopsis'>

<cmdsynopsis>
  <command>gpsfake</command>
      <arg choice='opt'>-1</arg>
      <arg choice='opt'>-h</arg>
      <arg choice='opt'>-b</arg>
      <arg choice='opt'>-c <replaceable>interval</replaceable></arg>
      <arg choice='opt'>-i</arg>
      <arg choice='opt'>-D <replaceable>debuglevel</replaceable></arg>
      <arg choice='opt'>-l</arg>
      <arg choice='opt'>-m <replaceable>monitor</replaceable></arg>
      <arg choice='opt'>-g</arg>
      <arg choice='opt'>-G</arg>
      <arg choice='opt'>-n</arg>
      <arg choice='opt'>-o <replaceable>options</replaceable></arg>
      <arg choice='opt'>-p</arg>
      <arg choice='opt'>-P <replaceable>port</replaceable></arg>
      <arg choice='opt'>-q</arg>
      <arg choice='opt'>-r <replaceable>initcmd</replaceable></arg>
      <arg choice='opt'>-s <replaceable>speed</replaceable></arg>
      <arg choice='opt'>-S</arg>
      <arg choice='opt'>-u</arg>
      <arg choice='opt'>-t</arg>
      <arg choice='opt'>-T</arg>
      <arg choice='opt'>-v</arg>
      <arg choice='opt'>-W <replaceable>timeout</replaceable></arg>
      <arg rep='repeat'>
            <arg choice='plain'><replaceable>logfile</replaceable></arg>
      </arg>
</cmdsynopsis>
</refsynopsisdiv>

<refsect1 id='description'><title>DESCRIPTION</title>

<para><application>gpsfake</application> is a test harness for
<application>gpsd</application> and its clients.  It opens a pty
(pseudo-TTY), launches a <application>gpsd</application> instance that
thinks the slave side of the pty is its GPS device, and repeatedly
feeds the contents of one or more test logfiles through the master side to the
GPS. If there are multiple logfiles, sentences from them are
interleaved in the order the files are specified.</para>

<para><application>gpsfake</application> does not require root
privileges, and can be run concurrently with a production
<application>gpsd</application> instance without causing problems.</para>

<para>The logfiles may contain packets in any supported format,
including in particular NMEA, SiRF, TSIP, or Zodiac.  Leading lines
beginning with # will be treated as comments and ignored, except in
the following special cases:</para>

<itemizedlist>
<listitem><para>
a comment of the form #Date: yyyy-mm-dd (ISO8601 date format) may be
used to set the initial date for the log.
</para></listitem>

<listitem><para>
a comment of the form #Serial: [0-9]* [78][NOE][12] may be used to set
serial parameters for the log - baud rate, word length, stop bits.
</para></listitem>

<listitem><para>
a comment of the form #Transport: UDP may be used to fake a UDP source
rather than the normal pty.
</para></listitem>
</itemizedlist>

<para>The <application>gpsd</application> instance is run in
foreground.  The thread sending fake GPS data to the daemon
is run in background.</para>

</refsect1>
<refsect1 id='options'><title>OPTIONS</title>

<para>With the -1 option, the logfile is interpreted once only rather
than repeatedly.  This option is intended to facilitate regression
testing.</para>

<para>The <option>-b</option> enables a twirling-baton progress indicator
on standard error.  At termination, it reports elapsed time.</para>

<para>The <option>-c</option> sets the delay between sentences in
seconds. Fractional values of seconds are legal.  The default is zero
(no delay).</para>

<para>The <option>-l</option> makes the program dump a line or packet number
just before each sentence is fed to the daemon. If the sentence is
textual (e.g. NMEA), the text is dumped as well.  If not, the packet
will be dumped in hexadecimal (except for RTCM packets, which aren't
dumped at all).  This option is useful for checking that gpsfake is
getting packet boundaries right.</para>

<para>The <option>-i</option> is for single-stepping through logfiles.  It dumps
the line or packet number (and the sentence if the protocol is
textual) followed by "? ".  Only when the user keys Enter is the line
actually fed to <application>gpsd</application>.</para>

<para>The <option>-m</option> specifies a monitor program inside which the
daemon should be run.  This option is intended to be used with
<citerefentry><refentrytitle>valgrind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gdb</refentrytitle><manvolnum>1</manvolnum></citerefentry>
and similar programs.</para>

<para>The <option>-g</option> and <option>-G</option> options use the monitor
facility to run the <application>gpsd</application> instance within gpsfake
under control of gdb or lldb, respectively.  They also disable the timeout on
daemon inactivity, to allow for breakpointing. If necessary, the timeout can be
reenabled by a subsequent <option>-W</option>.  If xterm and $DISPLAY are
available, these options launch the debugger in a separate xterm window, to
separate the debugger dialog from the program output, but otherwise run it
directly.  In the gdb case, -tui is used with xterm but not otherwise, since
curses and program output don't play nicely together.  Although lldb lacks an
equivalent option, some versions have a 'gui' command.</para>

<para>The <option>-o</option> specifies options to pass to the daemon.  The -n
option passes -n to start the daemon reading the GPS without waiting
for a client (equivalent to -o "-n").  The <option>-D</option> passes a -D
option to the daemon: thus -D 4 is shorthand for -o "-D 4".</para>

<para>The -p ("pipe") option sets watcher mode and dumps the NMEA and GPSD
notifications generated by the log to standard output. This is useful
for regression-testing.</para>

<para>The -P ("port") option sets the daemon's listening port.</para>

<para>The <option>-q</option> tells gpsfake to suppress normal progress
output and thus act in a quiet manner.</para>

<para>The <option>-r</option> specifies an initialization command to use in pipe mode.
The default is <command>?WATCH={"enable":true,"json":true}</command>.</para>

<para>The <option>-s</option> sets the baud rate for the slave tty.  The
default is 4800.</para>

<para>The option -S tells gpsfake to insert realistic delays in the
test input rather than trying to stuff it through the daemon as fast
as possible.  This will make the test(s) run much slower, but avoids
flaky failures due to machine load and possible race conditions in
the pty layer.</para>

<para>The <option>-t</option> forces the test framework to use TCP
rather than pty devices. Besides being a test of TCP source handling,
this may be useful for testing from within chroot jails where access
to pty devices is locked out.</para>

<para>The <option>-T</option> makes <application>gpsfake</application> print
some system information and then exit.</para>

<para>The <option>-u</option> forces the test framework to use UDP
rather than pty devices. Besides being a test of UDP source handling,
this may be useful for testing from within chroot jails where access
to pty devices is locked out.</para>

<para>The <option>-v</option> enables verbose progress reports to stderr.  It is
mainly useful for debugging <application>gpsfake</application>
itself.</para>

<para>The <option>-W</option> ("wait") option sets the timeout on daemon
inactivity, in seconds.  The default timeout is 60 seconds, and a value
of 0 suppresses the timeout altogether.  Note that the actual timeout is
longer due to internal delays, typically by about 20 seconds.</para>

<para>The <option>-x</option> dumps packets as
<application>gpsfake</application> gathers them.  It is mainly useful
for debugging <application>gpsfake</application> itself.</para>

<para>The <option>-h</option> makes <application>gpsfake</application> print
a usage message and exit.</para>

<para>The argument must be the name of a file containing the
data to be cycled at the device. <application>gpsfake</application>
will print a notification each time it cycles.</para>

<para>Normally, gpsfake creates a pty for each logfile and passes the
slave side of the device to the daemon.  If the header comment in the
logfile contains the string "UDP", packets are instead shipped via UDP
port 5000 to the address 192.168.0.1.255.  You can monitor them with
this: <command>tcpdump -s0 -n -A -i lo udp and port 5000</command>.</para>

</refsect1>
<refsect1 id='magic'><title>MAGIC COMMENTS</title>

<para>Certain magic comments in test load headers can change the
conditions of the test.  These are:</para>

<variablelist>
<varlistentry>
<term>Serial:</term>
<listitem><para>May contain a serial-port setting such as 4800 7N2 -
baud rate followed by 7 or 8 for byte length, N or O or E for parity
and 1 or 2 for stop bits. The test is run with those settings on the
slave port that the daemon sees.</para></listitem>
</varlistentry>
<varlistentry>
<term>Transport:</term>
<listitem><para>Values 'TCP' and 'UDP' force the use of TCP and
UDP feeds respectively (the default is a pty).</para></listitem>
</varlistentry>
<varlistentry>
<term>Delay-Cookie:</term>
<listitem><para>Must be followed by two whitespace-separated fields, a
delimiter character and a numeric delay in seconds. Instead of being
broken up by packet boundaries, the test load is split on the
delimiters.  The delay is performed after each feed.  Can be useful
for imposing write boundaries in the middle of packets.
</para></listitem>
</varlistentry>
</variablelist>

</refsect1>
<refsect1 id='custom'><title>CUSTOM TESTS</title>

<para><application>gpsfake</application> is a trivial wrapper around a
Python module, also named gpsfake, that can be used to fully script
sessions involving a <application>gpsd</application> instance, any
number of client sessions, and any number of fake GPSes feeding the
daemon instance with data from specified sentence logs.</para>

<para>Source and embedded documentation for this module is shipped with the
<application>gpsd</application> development tools.  You can use it to
torture-test either <application>gpsd</application> itself or any
<application>gpsd</application>-aware client application.</para>

<para>Logfiles for the use with <application>gpsfake</application> can
be retrieved using <application>gpspipe</application>,
<application>gpscat</application>, or
<application>gpsmon</application> from the gpsd distribution, or any
other application which is able to create a compatible output.</para>

<para>If <application>gpsfake</application> exits with "Cannot execute
gpsd: executable not found." the environment variable GPSD_HOME can be
set to the path where gpsd can be found. (instead of adding that folder
to the PATH environment variable</para>

</refsect1>
<refsect1 id='see_also'><title>SEE ALSO</title>
<para>
<citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gps</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>libgps</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>libgpsmm</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gpsctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gpspipe</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>gpsprof</refentrytitle><manvolnum>1</manvolnum></citerefentry>
<citerefentry><refentrytitle>gpsmon</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
</refsect1>

<refsect1 id='maintainer'><title>AUTHOR</title>

<para>Eric S. Raymond <email>esr@thyrsus.com</email>.</para>

</refsect1>

</refentry>