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. Running 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:

       •   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.

       •   a comment of the form #Transport: UDP may be used to fake a UDP source rather than the
           normal pty.

       •   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:

       •   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