gpsd/man/gpsfake.xml

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   "-//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'>-b</arg>
      <arg choice='opt'>--baton</arg>
      <arg choice='opt'>-c <replaceable>interval</replaceable></arg>
      <arg choice='opt'>--cycle <replaceable>interval</replaceable></arg>
      <arg choice='opt'>-D <replaceable>debuglevel</replaceable></arg>
      <arg choice='opt'>-g</arg>
      <arg choice='opt'>-G</arg>
      <arg choice='opt'>--gdb</arg>
      <arg choice='opt'>-h</arg>
      <arg choice='opt'>--help</arg>
      <arg choice='opt'>-i</arg>
      <arg choice='opt'>--initcmd <replaceable>initcmd</replaceable></arg>
      <arg choice='opt'>-l</arg>
      <arg choice='opt'>--linedump</arg>
      <arg choice='opt'>--lldb</arg>
      <arg choice='opt'>--monitor <replaceable>monitor</replaceable></arg>
      <arg choice='opt'>-m <replaceable>monitor</replaceable></arg>
      <arg choice='opt'>-n</arg>
      <arg choice='opt'>--nowait</arg>
      <arg choice='opt'>--options <replaceable>options</replaceable></arg>
      <arg choice='opt'>-o <replaceable>options</replaceable></arg>
      <arg choice='opt'>-p</arg>
      <arg choice='opt'>--pipe</arg>
      <arg choice='opt'>--port <replaceable>port</replaceable></arg>
      <arg choice='opt'>--predump</arg>
      <arg choice='opt'>-P <replaceable>port</replaceable></arg>
      <arg choice='opt'>--promptme</arg>
      <arg choice='opt'>-q</arg>
      <arg choice='opt'>--quiet</arg>
      <arg choice='opt'>-r <replaceable>initcmd</replaceable></arg>
      <arg choice='opt'>-S</arg>
      <arg choice='opt'>--singleshot</arg>
      <arg choice='opt'>--slow</arg>
      <arg choice='opt'>--speed <replaceable>speed</replaceable></arg>
      <arg choice='opt'>-s <replaceable>speed</replaceable></arg>
      <arg choice='opt'>-t</arg>
      <arg choice='opt'>-T</arg>
      <arg choice='opt'>--tcp</arg>
      <arg choice='opt'>--timeout <replaceable>timeout</replaceable></arg>
      <arg choice='opt'>-u</arg>
      <arg choice='opt'>--udp</arg>
      <arg choice='opt'>-v</arg>
      <arg choice='opt'>-V</arg>
      <arg choice='opt'>--verbose</arg>
      <arg choice='opt'>--version</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><option>-?</option>,<option>-h</option>, <option>--help</option>
makes <application>gpsfake</application> print a usage message and
exit.</para>

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

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

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

<para><option>-D</option>, <option>--debug</option> passes a -D option
to the daemon: thus -D 4 is shorthand for -o="-D 4".</para>

<para><option>-g</option>, <option>--gdb</option> or
<option>-G</option>, <option>--lldb</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> or <option>--wait</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><option>-i</option>, <option>--promptme</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><option>-l</option>, <option>--singleshot</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><option>-m</option>, <option>--monitor</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><option>-n</option>, <option>--nowait</option> passes "-n" to the
daemon to start the daemon reading the GPS without waiting for a client
(equivalent to -o="-n"). </para>

<para><option>-o</option>, <option>--option</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><option>-p</option>, <option>--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><option>-P</option>, <option>--port</option> sets the daemon's
listening port.</para>

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

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

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

<para><option>-S</option>, <option>--slow</option> 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><option>-t</option>, <option>--tcp</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><option>-T</option>, <option>--sysinfo</option> makes
<application>gpsfake</application> print some system information and
then exit.</para>

<para><option>-u</option>, <option>--udp</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><option>-v</option>, <option>--verbose</option> enables verbose
progress reports to stderr. Use multiple times to increase verbosity.
It is mainly useful for debugging <application>gpsfake</application>
itself.</para>

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

<para>The last argument(s) must be the name of a file or
files 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='environment'><title>ENVIRONMENT</title>

<para>For unknown reasons <application>gpsfake</application> may sometimes
time out and fail.  Set the WRITE_PAD environment value to a larger value
to avoid this issue.  A starting point might be "WRITE_PAD = 0.005".  Values
as large os 0.200 may be required.</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>