'\" t
.\"     Title: gpsfake
.\"    Author: Eric S. Raymond
.\" Generator: Asciidoctor 2.0.18
.\"      Date: 2023-01-10
.\"    Manual: GPSD Documentation
.\"    Source: GPSD, Version 3.25
.\"  Language: English
.\"
.TH "GPSFAKE" "1" "2023-01-10" "GPSD, Version 3.25" "GPSD Documentation"
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.SH "NAME"
gpsfake \- test harness for gpsd, simulating a GNSS receiver
.SH "SYNOPSIS"
.sp
\fBgpsfake\fP [OPTIONS] infile
.sp
\fBgpsfake\fP \-h
.sp
\fBgpsfake\fP \-V
.SH "DESCRIPTION"
.sp
\fBgpsfake\fP is a test harness for \fBgpsd\fP and its clients. It opens a pty
(pseudo\-TTY), launches a \fBgpsd\fP 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.
.sp
\fBgpsfake\fP does not require root privileges, but will run fine as root.
It can be run concurrently with a production \fBgpsd\fP instance without
causing problems, as long as you use the \fB\-P\fP option.  Runing under sudo
will cause minor loss of functionality.
.sp
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.
.sp
Thse are interpreted directly by \fBgpsfake\fP:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
a comment of the form \fB#Serial: [0\-9] [78][NOE][12]\fP may be used to set
serial parameters for the log \- baud rate, word length, stop bits.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
a comment of the form \fB#Transport: UDP\fP may be used to fake a UDP source
rather than the normal pty.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
a comment of the form \fB#Transport: TCP\fP may be used to fake a TCP source
rather than the normal pty.
.RE
.sp
Thse are interpreted directly by \fBgpsd\fP:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.  sp -1
.  IP \(bu 2.3
.\}
a comment of the form \fB# Date: yyyy\-mm\-dd\fP (ISO8601 date format) may be
used to set the initial date for the log.
.RE
.sp
The \fBgpsd\fP instance is run in foreground. The thread sending fake GNSS data
to the daemon is run in background.
.SH "OPTIONS"
.sp
\fB\-?\fP, \fB\-h\fP, \fB\-\-help\fP
.RS 4
Print a usage message and exit.
.RE
.sp
\fB\-1\fP, \fB\-\-singleshot\fP
.RS 4
The logfile is interpreted once only rather than repeatedly. This
option is intended to facilitate regression testing.
.RE
.sp
\fB\-b\fP, \fB\-\-baton\fP
.RS 4
Enable a twirling\-baton progress indicator on standard error. At
termination, it reports elapsed time.
.RE
.sp
\fB\-c COUNT\fP, \fB\-\-cycle COUNT\fP
.RS 4
Sets the delay between sentences in seconds. Fractional values of
seconds are legal. The default is zero (no delay).
.RE
.sp
\fB\-d LVL\fP, \fB\-\-debug LVL\fP
.RS 4
Pass a \fB\-D\fP option to the daemon: thus \fB\-D
4\fP is shorthand for \fB\-o="\-D 4"\fP.
.RE
.sp
\fB\-g\fP, \fB\-G\fP, \fB\-\-gdb\fP, \fB\-\-lldb\fP
.RS 4
Use the monitor facility to run the \fBgpsd\fP instance within \fBgpsfake\fP under
control of \fBgdb\fP or \fBlldb\fP, respectively. They also disable the timeout on
daemon inactivity, to allow for breakpointing. If necessary, the
timeout can be reenabled by a subsequent \fB\-W\fP or \fB\-\-wait\fP . If
\fBxterm\fP and $DISPLAY are available, these options launch the debugger in
a separate \fBxterm\fP window, to separate the debugger dialog from the
program output, but otherwise run it directly. In the \fBgdb\fP case,
\fB\-tui\fP is used with \fBxterm\fP but not otherwise, since curses and
program output don\(cqt play nicely together. Although \fBlldb\fP lacks an
equivalent option, some versions have a \*(Aqgui\*(Aq command.
.RE
.sp
\fB\-i\fP, \fB\-\-promptme\fP
.RS 4
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 \fBgpsd\fP.
.RE
.sp
\fB\-l\fP, \fB\-\-linedump\fP
.RS 4
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\(cqt dumped at all). This option is useful for
checking that \fBgpsfake\fP is getting packet boundaries right.
.RE
.sp
\fB\-m PROG\fP, \fB\-\-monitor PROG\fP
.RS 4
Specify a monitor program (PROG) inside which the daemon should be
run. This option is intended to be used with \fBvalgrind\fP(1) , \fBgdb\fP(1) and
similar programs.
.RE
.sp
\fB\-n\fP, \fB\-\-nowait\fP
.RS 4
Pass \fB\-n\fP to the daemon to start the daemon reading the GNSS receiver
without waiting for a client (equivalent to \fB\-o="\-n"\fP).
.RE
.sp
\fB\-o="OPTS"\fP, \fB\-\-option="OPTS"\fP
.RS 4
Specify options to pass to the daemon. The equal sign (=) and quotes
are required so that \fBgpsd\fP options are not confused with \fBgpsfake\fP
options. To start the daemon reading the GNSS receiver without waiting
for a client use \fB\-o="\-n"\fP (equivalent to the \fB\-n\fP) which passes \fB\-n\fP
to the \fBgpsd\fP daemon. The option \fB\-o="\-D 4"\fP passes a \fB\-D 4\fP to the
daemon, equivalent to the using \fB\-D 4\fP.
.RE
.sp
\fB\-p\fP, \fB\-\-pipe\fP
.RS 4
Sets watcher mode and dump the NMEA and GPSD notifications generated
by the log to standard output. This is useful for regression testing.
.RE
.sp
\fB\-p PORT\fP, \fB\-\-port PORT\fP
.RS 4
Sets the daemon\(cqs listening port to PORT.
.RE
.sp
\fB\-q\fP, \fB\-\-quiet\fP
.RS 4
Tell \fBgpsfake\fP to suppress normal progress output and thus act in a
quiet manner.
.RE
.sp
\fB\-r STR\fP, \fB\-\-clientinit STR\fP
.RS 4
Specify an initialization command to use in pipe mode. The default is
\fB?WATCH={"enable":true,"json":true}\fP.
.RE
.sp
\fB\-s SPEED\fP, \fB\-\-speed SPEED\fP
.RS 4
Sets the baud rate for the slave tty. The default is 4800.
.RE
.sp
\fB\-S\fP, \fB\-\-slow\fP
.RS 4
Tells \fBgpsfake\fP 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.
.RE
.sp
\fB\-t\fP, \fB\-\-tcp\fP
.RS 4
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.
.RE
.sp
\fB\-T\fP, \fB\-\-sysinfo\fP
.RS 4
Makes \fBgpsfake\fP print some system information and then exit.
.RE
.sp
\fB\-u\fP, \fB\-\-udp\fP
.RS 4
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.
.RE
.sp
\fB\-v\fP, \fB\-\-verbose\fP
.RS 4
Enable verbose progress reports to stderr. Use multiple times to
increase verbosity. It is mainly useful for debugging \fBgpsfake\fP itself.
.RE
.sp
\fB\-w SEC\fP, \fB\-\-wait SEC\fP
.RS 4
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.
.RE
.sp
\fB\-x\fP, \fB\-\-predump\fP
.RS 4
Dump packets as \fBgpsfake\fP gathers them. It is mainly useful for
debugging \fBgpsfake\fP itself.
.RE
.sp
The last argument(s) must be the name of a file or files containing the
data to be cycled at the device. \fBgpsfake\fP will print a notification each
time it cycles.
.sp
Normally, \fBgpsfake\fP 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 \fBtcpdump\fP
this way:
.sp
.if n .RS 4
.nf
.fam C
tcpdump \-s0 \-n \-A \-i lo udp and port 5000
.fam
.fi
.if n .RE
.SH "MAGIC COMMENTS"
.sp
Certain magic comments in test load headers can change the conditions of
the test. These are:
.sp
\fBSerial\fP
.RS 4
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.
.RE
.sp
\fBTransport\fP
.RS 4
Values \*(AqTCP\*(Aq and \*(AqUDP\*(Aq force the use of TCP and UDP feeds respectively
(the default is a pty).
.RE
.sp
\fBDelay\-Cookie\fP
.RS 4
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.
.RE
.SH "CUSTOM TESTS"
.sp
\fBgpsfake\fP is a trivial wrapper around a Python module, also named \fBgpsfake\fP,
that can be used to fully script sessions involving a \fBgpsd\fP instance, any
number of client sessions, and any number of fake GPSes feeding the
daemon instance with data from specified sentence logs.
.sp
Source and embedded documentation for this module is shipped with the
\fBgpsd\fP development tools. You can use it to torture test either \fBgpsd\fP
itself or any \fBgpsd\fP\-aware client application.
.sp
Logfiles for the use with \fBgpsfake\fP can be retrieved using \fBgpspipe\fP,
\fBgpscat\fP, or \fBcgps\fP from the \fBgpsd\fP distribution, or any other application
which is able to create a compatible output.
.SH "ENVIRONMENT"
.SS "WRITE_PAD"
.sp
For unknown reasons \fBgpsfake\fP 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.
.SS "GPSD_HOME"
.sp
If \fBgpsfake\fP exits with "Cannot execute gpsd: executable not found." the
environment variable GPSD_HOME can be set to the path where \fBgpsd\fP can be
found. (instead of adding that folder to the PATH environment variable
.SH "RETURN VALUES"
.sp
\fB0\fP
.RS 4
on success.
.RE
.sp
\fB1\fP
.RS 4
on failure
.RE
.SH "SEE ALSO"
.sp
\fBgpsd\fP(8), \fBgps\fP(1), \fBgpspipe\fP(1), \fBgpscat\fP(1), \fBcgps\fP(1), \fBtcpdump\fP(1),
\fBgdb\fP(1), \fBlldb\fP(1), \fBvalgrind\fP(1)
.SH "RESOURCES"
.sp
\fBProject web site:\fP \c
.URL "https://gpsd.io/" "" ""
.SH "COPYING"
.sp
This file is Copyright 2013 by the GPSD project
.br
SPDX\-License\-Identifier: BSD\-2\-clause
.SH "AUTHOR"
.sp
Eric S. Raymond