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gpsfake(1)                    GPSD Documentation                    gpsfake(1)




NAME

       gpsfake - test harness for gpsd, simulating a GPS


SYNOPSIS

       gpsfake [-?] [--baton] [--cycle interval] [--gdb] [--help]
               [--initcmd initcmd] [--linedump] [--lldb] [--monitor monitor]
               [--nowait] [--options=options] [--pipe] [--port port]
               [--predump] [--promptme] [--quiet] [--singleshot] [--slow]
               [--speed speed] [--tcp] [--timeout timeout] [--udp] [--verbose]
               [--version] [-1] [-b] [-c interval] [-D debuglevel] [-g] [-G]
               [-h] [-i] [-l] [-m monitor] [-n] [-o=options] [-p] [-P port]
               [-q] [-r initcmd] [-S] [-s speed] [-t] [-T] [-u] [-v] [-V]
               [-W timeout] [logfile...]


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 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.

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

       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:

       o   a comment of the form #Date: yyyy-mm-dd (ISO8601 date format) may
           be used to set the initial date for the log.

       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.

       The gpsd instance is run in foreground. The thread sending fake GPS
       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 GPS 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 GPS 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 them with this:
       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 gpsmon from the gpsd distribution, or any other application
       which is able to create a compatible output.

       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


ENVIRONMENT

       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.


SEE ALSO

       gpsd(8), gps(1), libgps(3), libgpsmm(3), gpsctl(1), gpspipe(1),
       gpsprof(1) gpsmon(1).


AUTHOR

       Eric S. Raymond <esr@thyrsus.com>.



The GPSD Project               10 December 2020                     gpsfake(1)

gpsd 3.22 - Generated Sat Jan 16 11:12:11 CST 2021
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