gpsfake(1) GPSD Documentation gpsfake(1)
NAME
gpsfake - test harness for gpsd, simulating a GNSS receiver
SYNOPSIS
gpsfake [OPTIONS] infile
gpsfake -h
gpsfake -V
DESCRIPTION
gpsfake is a test harness for gpsd and its clients. It opens a pty
(pseudo-TTY), launches a gpsd instance that thinks the slave side of the
pty is its GNSS device, and repeatedly feeds the contents of one or more
test logfiles through the master side to the GNSS receiver. If there are
multiple logfiles, sentences from them are interleaved in the order the
files are specified.
gpsfake does not require root privileges, but will run fine as root. It
can be run concurrently with a production gpsd instance without causing
problems, as long as you use the -P option. Runing under sudo will cause
minor loss of functionality.
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.
Thse are interpreted directly by gpsfake:
o 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.
o a comment of the form #Transport: UDP may be used to fake a UDP
source rather than the normal pty.
o a comment of the form #Transport: TCP may be used to fake a TCP
source rather than the normal pty.
Thse are interpreted directly by gpsd:
o a comment of the form # Date: yyyy-mm-dd (ISO8601 date format) may be
used to set the initial date for the log.
The gpsd instance is run in foreground. The thread sending fake GNSS data
to the daemon is run in background.
OPTIONS
-?, -h, --help
Print a usage message and exit.
-1, --singleshot
The logfile is interpreted once only rather than repeatedly. This
option is intended to facilitate regression testing.
-b, --baton
Enable a twirling-baton progress indicator on standard error. At
termination, it reports elapsed time.
-c COUNT, --cycle COUNT
Sets the delay between sentences in seconds. Fractional values of
seconds are legal. The default is zero (no delay).
-d LVL, --debug LVL
Pass a -D option to the daemon: thus -D 4 is shorthand for -o="-D 4".
-g, -G, --gdb, --lldb
Use the monitor facility to run the gpsd 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 -W or --wait
. 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.
-i, --promptme
Single-step 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 gpsd.
-l, --linedump
Print 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 printed
as well. If not, the packet will be printed 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.
-m PROG, --monitor PROG
Specify a monitor program (PROG) inside which the daemon should be
run. This option is intended to be used with valgrind(1) , gdb(1) and
similar programs.
-n, --nowait
Pass -n to the daemon to start the daemon reading the GNSS receiver
without waiting for a client (equivalent to -o="-n").
-o="OPTS", --option="OPTS"
Specify options to pass to the daemon. The equal sign (=) and quotes
are required so that gpsd options are not confused with gpsfake
options. To start the daemon reading the GNSS receiver without
waiting for a client use -o="-n" (equivalent to the -n) which passes
-n to the gpsd daemon. The option -o="-D 4" passes a -D 4 to the
daemon, equivalent to the using -D 4.
-p, --pipe
Sets watcher mode and dump the NMEA and GPSD notifications generated
by the log to standard output. This is useful for regression testing.
-p PORT, --port PORT
Sets the daemon's listening port to PORT.
-q, --quiet
Tell gpsfake to suppress normal progress output and thus act in a
quiet manner.
-r STR, --clientinit STR
Specify an initialization command to use in pipe mode. The default is
?WATCH={"enable":true,"json":true}.
-s SPEED, --speed SPEED
Sets the baud rate for the slave tty. The default is 4800.
-S, --slow
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.
-t, --tcp
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.
-T, --sysinfo
Makes gpsfake print some system information and then exit.
-u, --udp
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.
-v, --verbose
Enable verbose progress reports to stderr. Use multiple times to
increase verbosity. It is mainly useful for debugging gpsfake itself.
-w SEC, --wait SEC
Set 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.
-x, --predump
Dump packets as gpsfake gathers them. It is mainly useful for
debugging gpsfake itself.
The last argument(s) must be the name of a file or files containing the
data to be cycled at the device. gpsfake will print a notification each
time it cycles.
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 the packet with tcpdump
this way:
tcpdump -s0 -n -A -i lo udp and port 5000
MAGIC COMMENTS
Certain magic comments in test load headers can change the conditions of
the test. These are:
Serial
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.
Transport
Values 'TCP' and 'UDP' force the use of TCP and UDP feeds
respectively (the default is a pty).
Delay-Cookie
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.
CUSTOM TESTS
gpsfake is a trivial wrapper around a Python module, also named gpsfake,
that can be used to fully script sessions involving a gpsd instance, any
number of client sessions, and any number of fake GPSes feeding the
daemon instance with data from specified sentence logs.
Source and embedded documentation for this module is shipped with the
gpsd development tools. You can use it to torture test either gpsd itself
or any gpsd-aware client application.
Logfiles for the use with gpsfake can be retrieved using gpspipe, gpscat,
or cgps from the gpsd distribution, or any other application which is
able to create a compatible output.
ENVIRONMENT
WRITE_PAD
For unknown reasons gpsfake 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.
GPSD_HOME
If gpsfake 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
RETURN VALUES
0
on success.
1
on failure
SEE ALSO
gpsd(8), gps(1), gpspipe(1), gpscat(1), cgps(1), tcpdump(1), gdb(1),
lldb(1), valgrind(1)
RESOURCES
Project web site: <https://gpsd.io/>
COPYING
This file is Copyright 2013 by the GPSD project
SPDX-License-Identifier: BSD-2-clause
AUTHOR
Eric S. Raymond
GPSD, Version 3.24 2021-09-20 gpsfake(1)
mgpsd 3.24 - Generated Sun Jan 1 09:26:44 CST 2023