--- name: "fgfs" section: "1" platform: "linux" package: "flightgear" version: "1:2020.3.19+dfsg-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/fgfs" --- # fgfs(1) the FlightGear flight simulator ## NAME fgfs - the FlightGear flight simulator ## SYNOPSIS **fgfs** \[*options...*\] ## DESCRIPTION **fgfs** is the main executable for FlightGear, a free, open-source, multi-platform and sophisticated flight simulator framework for the development and pursuit of interesting flight simulator ideas. ## OPTIONS Options are first read from the command-line arguments passed to **fgfs**. The program then checks for the existence of *~/.fgfsrc.hostname* (where *hostname* is the hostname of the machine) and of *~/.fgfsrc*; if at least one of those files exists, it is read and parsed (see the [**fgfsrc**(5)](/fgfsrc/5.md) man page for the full specifications of the file format). If conflicting options are given, the ones read last will prevail. ### General options - **--help**, **-h** Display usage information about the most relevant command-line options and exit. - **--verbose**, **-v** When combined with **--help**/**-h**, display usage information about all command-line options, not just the most relevant ones. - **--version** Display version information about **fgfs** and some of the libraries used by the program (SimGear, OpenSceneGraph, PLIB), then exit. - **--fg-root=***path* Set the FlightGear data root directory (**$FG\_ROOT**) to *path*. If this option is not set, **fgfs** uses the path specified in the **FG\_ROOT** environment variable or, absent that, the FlightGear data directory chosen at the time the program was compiled. - **--fg-scenery=***path* Set the FlightGear scenery directories (**$FG\_SCENERY**) to *path*. You can specify multiple directories by separating them with colons (**:**), as in */first/path***:***/second/path* (on Microsoft Windows operating systems, multiple paths should be separated by semicolons instead): in that case, **fgfs** will follow the order the paths are written in to search for scenery files, stopping as soon as a match is found. If this option is not set, **fgfs** uses the path specified in the **FG\_SCENERY** environment variable or, absent that, the **Scenery** subdirectory inside **$FG\_ROOT**. - **--fg-aircraft=***path* Load additional aircraft from *path* besides the **Aircraft** subdirectory inside **$FG\_ROOT**. Alternatively, you can use **--aircraft-dir** to target a specific aircraft in a given directory. - **--download-dir=***path* Store aircraft and scenery downloaded via the simulator in *path*. The TerraSync directory may be specifically set with the **--terrasync-dir** option. - **--allow-nasal-read=***dirs* Allow Nasal aircraft scripts to read files from the directories listed in *dirs* (separate multiple paths with colons, or semicolons on Microsoft Windows operating systems). By default, Nasal scripts are allowed to read data only from **$FG\_ROOT** and **$FG\_HOME**, as a security measure. - **--read-only** Make **$FG\_HOME** (the location where user-specific FlightGear data is stored) read-only. - **--language=***code* Set the language used by the simulator to *code*, where *code* is an ISO 639-1 two-letter locale code (for example, **en** or **it**). - **--restore-defaults** Reset all user settings to their defaults. - **--enable-save-on-exit**, **--disable-save-on-exit** Save/do not save user settings when the program exits. - **--ignore-autosave** Ignore the user settings saved the previous time FlightGear was run. This option implies **--disable-save-on-exit**. - **--browser-app=***path* Use the Web browser specified in *path* to open aircraft documentation. - **--prop:**\[*type***:**\]*name***=***value* Set the property *name* to *value*. You can optionally specify the property type by setting *type* to **string**, **double**, **float**, **long**, **int** or **bool**. - **--config=***path* Load additional configuration directives from *path*. The file should follow the format described in [**fgfsrc**(5)](/fgfsrc/5.md). - **--no-default-config** Do not load any configuration files unless they were explicitly specified with **--config**. - **--units-feet** Use feet as the internal measure unit for distances. - **--units-meters** Use meters as the internal measure unit for distances. - **--console** Display a console window for simulator/aircraft debugging purposes. This option is recognized only on Microsoft Windows operating systems; on other systems, debug messages are always printed to standard output/standard error. - **--launcher** Start the FlightGear Launcher, a graphical Qt-based interface to the simulator. This option is available only if FlightGear was compiled with Qt support enabled. - **--json-report** Print a report in JSON format on the standard output. The report will give useful information for debugging purposes, such as the FlightGear version, the scenery/aircraft paths in use, the TerraSync and the data download directories and the paths to navigation data files. ### Features - **--enable-panel**, **--disable-panel** Enable/disable the pop-up aircraft instrument panel if the chosen airplane has it. - **--enable-hud**, **--disable-hud** Enable/disable the heads-up display (HUD) if the chosen airplane has it. - **--enable-anti-alias-hud**, **--disable-anti-alias-hud** Enable/disable heads-up display antialiasing. - **--enable-hud-3d**, **--disable-hud-3d** Enable/disable the 3D version of the heads-up display. - **--hud-tris** Display the number of triangles rendered when painting the heads-up display. - **--hud-culled** Display the number of triangles culled when painting the heads-up display. - **--enable-random-objects**, **--disable-random-objects** Show/hide random scenery objects, such as buildings. Scenery objects increase realism, but require more resources (memory and graphic card power). - **--enable-random-vegetation**, **--disable-random-vegetation** Show/hide random vegetation. - **--enable-random-buildings**, **--disable-random-buildings** Show/hide random buildings. - **--enable-ai-models**, **--disable-ai-models** Enable/disable the internal AI subsystem, which is required for multiplayer gaming, AI traffic and many other animations. **Disabling the internal AI** **subsystem is deprecated.** - **--enable-ai-traffic**, **--disable-ai-traffic** Enable/disable artificial plane traffic. - **--ai-scenario=***scenario* Add and enable the AI scenario *scenario*. This option may be repeated multiple times to enable multiple scenarios. - **--enable-freeze** Start the simulator in a frozen (paused) state. - **--disable-freeze** Start the simulator in a running (unpaused) state. - **--enable-fuel-freeze** Do not consume any fuel (keep its quantity in the tanks constant). - **--disable-fuel-freeze** Consume fuel normally. - **--enable-clock-freeze** Do not let the clock advance while running the simulation. - **--disable-clock-freeze** Let the clock advance normally. - **--failure=pitot**\|**static**\|**vacuum**\|**electrical** Fail the aircraft pitot, static, vacuum or electrical systems. This option may be repeated multiple times to fail more than one system. - **--load-tape=***tape* Load and replay the flight recorder tape *tape*. ### Audio options - **--show-sound-devices** Show a list of available audio devices and exit. - **--sound-device=***name* Set the sound device to use to *name*, where *name* is the device name shown by the **--show-sound-devices** option. - **--enable-sound**, **--disable-sound** Enable/disable sound in the simulator. ### Rendering options - **--terrain-engine=tilecache**\|**pagedLOD** Choose the terrain engine to use. **tilecache** is the "traditional" terrain engine (recommended); **pagedLOD** is a new, experimental terrain engine designed to minimize memory usage by loading more detailed versions of scenery objects on demand. The **pagedLOD** engine is available only if FlightGear was compiled with GDAL support. - **--lod-levels=***levels* Set the level of detail levels to *levels*, where *levels* is a space-separated list of numeric levels. This option is available only if the terrain engine in use is **pagedLOD**. - **--lod-res=***resolution* Set the terrain mesh resolution to *resolution*. This option is available only if the terrain engine in use is **pagedLOD**. - **--lod-texturing=bluemarble**\|**raster**\|**debug** Set the terrain texture method. This option is available only if the terrain engine in use is **pagedLOD**. - **--lod-range-mult=***multiplier* Set the range multiplier (the breakpoint from a low to a high level of detail) to *multiplier*. This option is available only if the terrain engine in use is **pagedLOD**. - **--enable-rembrandt**, **--disable-rembrandt** Enable/disable the Rembrandt engine ⟨http://\\:wiki.flightgear.org/\\:Project\_Rembrandt⟩, which adds deferred shading (rendering all properties of an object, such as shading, lighting, fog) in more than one pass. - **--renderer=***name* If the Rembrandt engine is enabled, use the rendering pipeline described in *$FG\_ROOT/Effects/*name*.xml*. - **--enable-splash-screen**, **--disable-splash-screen** Show/hide the simulator splash screen while loading the aircraft/scenery. - **--enable-mouse-pointer**, **--disable-mouse-pointer** Force enable display/do not force display the mouse pointer at startup. - **--max-fps=***frequency* Limit the maximum frame rate of the simulator to *frequency* Hz (frames per second). - **--bpp=***depth* Use a color depth of *depth* bits per pixel to display the aircraft and scenery. - **--fog-disable**, **--fog-fastest**, **--fog-nicest** Choose the fog/haze rendering technique. **--fog-disable** will disable fog/haze entirely; **--fog-fastest** will explicitly ask the graphics card driver to choose the most efficient, but possibly less accurate, fog/haze rendering algorithm; **--fog-nicest** will leave the algorithm choice to the driver, leading to higher quality results. - **--enable-enhanced-lighting**, **--disable-enhanced-lighting** Enable/disable enhanced runway lighting. **This option is deprecated.** - **--enable-distance-attenuation**, **--disable-distance-attenuation** Enable/disable runway light distance attenuation (the runway lights become less intense as distance increases). - **--enable-horizon-effect**, **--disable-horizon-effect** Enable/disable the celestial body growth illusion near the horizon. - **--enable-specular-highlight**, **--disable-specular-highlight** Enable/disable specular reflections on textured objects. - **--fov=***degrees* Set the field of view angle (FOV) to *degrees*. High field of view angles allow you to see a wider part of the world; low angles allow you to "zoom in" on details. - **--aspect-ratio-multiplier=***factor* Set the horizontal and vertical aspect ratio multiplier to *factor*. - **--enable-fullscreen**, **--disable-fullscreen** Enable/disable fullscreen mode. - **--shading-flat**, **--shading-smooth** Use flat/smooth shading. If flat shading is active, the simulator uses the same color to paint the face of an object: this is faster, but makes edges more pronounced. Smooth shading smooths color changes between vertices, leading to higher-quality results, at an expense in performance. - **--materials-file=***file* Load the definitions of the materials used to render the scenery from *file*. By default, materials are loaded from *$FG\_ROOT/regions/materials.xml*. - **--texture-filtering=***value* Set the anisotropic texture filtering to *value*. The acceptable values are **1** (default), **2**, **4**, **8** or **16**. - **--enable-wireframe**, **--disable-wireframe** Enable/disable the wireframe drawing mode (in which only object edges are painted). - **--geometry=***width***x***height* Set the window geometry (size) to *width***x***height* (both *width* and *height* are in pixels). - **--view-offset=LEFT**\|**RIGHT**\|**CENTER**\|*value* Specify the default forward view direction as an offset from straight ahead. The allowed values are **LEFT** (-90°), **RIGHT** (90°), **CENTER** (0°) or a specific number in degrees. ### Aircraft options - **--aircraft=***name*, **--vehicle=***name* Load an aircraft/vehicle from a set file named name*-set.xml*. The file is searched for in *$FG\_ROOT/Aircraft*, in the directory pointed to by the environment variable **FG\_AIRCRAFT** and in the directories passed to [**fgfs**(1)](/fgfs/1.md) using the **--fg-aircraft** option. - **--aircraft-dir=***path* Explicitly specify the directory in which the **-set.xml** file should be searched for. If this argument is used, the path cache stored in *~/.fgfs/autosave\_X\_Y.xml*, the directories passed with the **--fg-aircraft** option and the directory specified in the **FG\_AIRCRAFT** environment variable are not taken into account. - **--show-aircraft** Print a list of available aircraft and exit. - **--min-status=alpha**\|**beta**\|**early-production**\|**production** Do not list aircraft having a status level (development status) lower than the one specified. See the FlightGear wiki "Aircraft rating system" page ⟨http://\\:wiki.flightgear.org/\\:Aircraft\_rating\_system⟩ for an extended description of aircraft ratings. - **--fdm=jsb**\|**larcsim**\|**yasim**\|**magic**\|**balloon**\|**ada**\|**external**\|**null** Select the core flight dynamics model to use among the following ones: - • **jsb**: the JSBSim flight dynamics model ⟨http://\\:www.jsbsim.org/⟩, which takes a data-driven approach to modeling: given the performance data for an aircraft (mass and balance, ground reactions, propulsions, aerodynamics...), it assembles it together to produce the global aircraft dynamics; - • **larcsim**: the LaRCsim flight dynamics model ⟨http://\\:www.jsbsim.org/⟩, the original model used in FlightGear up to 2000, developed at NASA, now inactive; - • **yasim**: the YASim flight dynamics model ⟨http://\\:wiki.flightgear.org/\\:YASim⟩, which, given the physical and flying characteristics of an aircraft, attempts to solve for them; - • **magic**: the "Magic Carpet" flight model; - • **balloon**: a hot air balloon simulation; - • **ada**: an externally-driven flight dynamics model designed by the Aeronautical Development Agency of Bangalore, India; - • **external**/**null**: use an external flight dynamics model (the **external** option has the same meaning as **null** and is maintained for backward compatibility purposes). - **--aero=***name* Load the aircraft aerodynamics model from the file name*.xml* in the aircraft directory. - **--model-hz=***n* Run the flight dynamics model at a frequency of *n* Hz (*n* times per second). - **--speed=***n* Run the flight dynamics model *n* times faster than real time. - **--trim**, **--notrim** Trim/do not attempt to trim the model. This option is only valid if the flight dynamics module in use is JSBSim. - **--on-ground** Start the aircraft on the ground. This is the default option. - **--in-air** Start the aircraft in the air. This option is implied if **--altitude** is specified. - **--enable-auto-coordination**, **--disable-auto-coordination** Enable/disable auto coordination (joint control of rudder and ailerons). - **--livery=***name* Load the aircraft livery from a file named *name*. - **--state=***value* Set the initial aircraft state to *value*. The states that can be used are aircraft-dependent. ### Time options - **--timeofday=real**\|**dawn**\|**morning**\|**noon**\|**afternoon**\|**dusk**\|**evening**\|**midnight** Start the simulator at the specified time of day: - • **real**: real clock time; - • **dawn**: the time when the Sun is 90° E on the horizon; - • **morning**: the time when the Sun is 75° E on the horizon; - • **noon**: the time when the Sun is 0° on the horizon; - • **afternoon**: the time when the Sun is 75° W on the horizon; - • **dusk**: the time when the Sun is 90° W on the horizon; - • **evening**: the time when the Sun is 100° W on the horizon; - • **midnight**: the time when the Sun is 180° on the horizon. - **--season=summer**\|**winter** Load summer/winter textures. - **--time-offset=**\[**+**\|**-**\]*hh***:***mm***:***ss* Add a time offset to the startup time specified with the **--timeofday** option. - **--time-match-real** Synchronize the simulator time with real world GMT time. - **--time-match-local** Synchronize the simulator time with real world local time. - **--start-date-sys=***yyyy***:***mm***:***dd***:***hh***:***mm***:***ss* Specify the simulator starting date and time with respect to the local timezone of the system. - **--start-date-gmt=***yyyy***:***mm***:***dd***:***hh***:***mm***:***ss* Specify the simulator starting date and time with respect to the Greenwich Mean Time. - **--start-date-lat=***yyyy***:***mm***:***dd***:***hh***:***mm***:***ss* Specify the simulator starting date and time with respect to the timezone of the starting airport. ### Initial position and orientation - **--airport=***ID* Start the simulator at the airport having *ID* as its ICAO code. - **--parking-id=***name* Place the aircraft at the parking position *name*. This option requires the **--airport** option to be present. - **--runway=***number* Place the aircraft on runway *number*. This option requires the **--airport** option to be present. - **--carrier=***name*\|*ID* Place the aircraft on the AI carrier named *name*/having the ID *ID*. - **--parkpos=***name* Place the aircraft at the starting position *name*. This option requires the **--carrier** option to be present. - **--vor=***ID* Place the aircraft over the VOR *ID*. - **--vor-frequency=***frequency* Set the frequency of the VOR to *frequency*. This option requires the **--vor** option to be present. - **--ndb=***ID* Place the aircraft over the NDB *ID*. - **--ndb-frequency=***frequency* Set the frequency of the NDB to *frequency*. This option requires the **--ndb** option to be present. - **--fix=***ID* Place the aircraft over the fix *ID*. - **--offset-distance=***nm* Place the aircraft *nm* statute miles away from the reference point specified by the previous options. - **--offset-azimuth=***degrees* Place the aircraft at a heading of *degrees* degrees with respect to the reference point specified by the previous options. - **--lon=***degrees*, **--lat=***degrees* Place the aircraft at the point with the coordinates (*lat*, *lon*). Northern longitudes/eastern latitudes must be positive; southern longitudes/western latitudes must be negative. - **--altitude=***value* Place the aircraft at an altitude of *value* feet (meters if the **--units-meters** option was specified). - **--heading=***degrees* Specify the initial heading (yaw) angle (psi) of the aircraft. - **--roll=***degrees* Specify the initial roll angle (phi) of the aircraft. - **--pitch=***degrees* Specify the initial pitch angle (theta) of the aircraft. - **--uBody=***units\_per\_sec* Specify the initial velocity along the body X axis. - **--vBody=***units\_per\_sec* Specify the initial velocity along the body Y axis. - **--wBody=***units\_per\_sec* Specify the initial velocity along the body Z axis. - **--vNorth=***units\_per\_sec* Specify the initial velocity along the body North-South axis. - **--vEast=***units\_per\_sec* Specify the initial velocity along the body West-East axis. - **--vDown=***units\_per\_sec* Specify the initial velocity along the body vertical axis. - **--vc=***knots* Set the initial airspeed of the aircraft to *knots* knots. - **--mach=***number* Set the initial airspeed of the aircraft to Mach *number*. - **--glideslope=***degrees* Set the flight path angle to *degrees* degrees. The value can be positive. - **--roc=***fpm* Set the initial rate of climb to *fpm* feet per minute. The value can be negative. ### Route/waypoint options - **--wp=***ID*\[**@***alt*\] Enter the waypoint (VOR, NDB, fix) *ID* into the autopilot. The optional part **@***alt* can be used to specify the altitude at which *ID* should be crossed. - **--flight-plan=***file* Read a flight plan from *file*. ### Avionics options - **--com1=***frequency* Set the COM1 frequency to *frequency* MHz. - **--com2=***frequency* Set the COM2 frequency to *frequency* MHz. - **--nav1=**\[*radial***:**\]*frequency* Set the NAV1 frequency to *frequency* MHz. You can optionally specify a radial by prefixing the frequency with the heading and a colon. - **--nav2=**\[*radial***:**\]*frequency* Set the NAV2 frequency to *frequency* MHz. You can optionally specify a radial by prefixing the frequency with the heading and a colon. - **--adf1=**\[*rotation***:**\]*frequency*, **--adf=**\[*rotation***:**\]*frequency* Set the ADF1 frequency to *frequency* kHz. You can optionally specify the rotation angle of its compass card by prefixing the frequency with the angle and a colon. **The --adf option is deprecated.** - **--adf2=**\[*rotation***:**\]*frequency* Set the ADF2 frequency to *frequency* kHz. You can optionally specify the rotation angle of its compass card by prefixing the frequency with the angle and a colon. - **--dme=nav1**\|**nav2**\|*frequency* Slave the automatic direction finder to the NAV1/NAV2 radio or set its internal frequency to *frequency*. ### Environment options - **--metar=***METAR* Simulate the weather conditions described by the METAR string *METAR*. This option implies **--disable-real-weather-fetch**. - **--enable-real-weather-fetch**, **--disable-real-weather-fetch** Enable/disable METAR-based real weather fetching. This feature requires an active Internet connection. - **--enable-clouds**, **--disable-clouds** Enable/disable 2D (flat) cloud layers. - **--enable-clouds3d**, **--disable-clouds3d** Enable/disable 3D (volumetric) cloud layers. - **--visibility=***meters* Set the initial visibility to *meters* meters. - **--visibility-miles=***miles* Set the initial visibility to *miles* miles. - **--wind=***dir*\[**:***maxdir*\]**@***speed*\[**:***gust*\] Specify the direction the wind blows from (*dir*) and its speed (*speed* knots). If the wind is not meant to blow from a fixed direction, but rather from a range of directions, specify the range as *dir***:***maxdir*, where *dir* and *maxdir* are the minimum and maximum angles in degrees. If you want the simulator to model wind gusts as well, set *gust* to their maximum intensity in knots. - **--random-wind** Randomize the direction and speed of the wind. - **--turbulence=***intensity* Set the turbulence intensity to *intensity*. The intensity can range from **0.0** (calm) to **1.0** (severe). - **--ceiling=***ft\_asl*\[**:***thickness\_ft*\] Create an overcast ceiling at a height of *ft\_asl* feet above the mean sea level. You can optionally specify a thickness by appending a colon (**:**) and the desired thickness in feet; if you omit it, the simulator will default to 2000 ft. ### Network options - **--callsign=***value* Set the multiplayer callsign to *value*. The callsign must be at most ten characters long and must contain only numbers, letters of the English alphabet, dashes (**-**) and underscores (**\_**); longer callsigns are truncated, and characters not matching those listed above are replaced with dashes. - **--multiplay=**{**in**\|**out**}**,***hz***,***address***,***port* Specify the multiplayer communication settings. The first field specifies whether the settings apply to inbound (**in**) or outbound (**out**) communications. The second field (*hz*) specifies the frequency (in Hz, times per second) at which data should be sent. The third field (*address*) must be set to the IP address of the network interface that FlightGear should use to send/receive data, or left blank to let the simulator use all available interfaces. The fourth field (*port*) should be set to the port to use (usually **5000**). - **--proxy=**\[*username***:***password***@**\]*host***:***port* Specify the proxy server and port to use. The username and password are optional; if they are present, they should be given as MD5 hashes. This option is only useful if **--real-weather-fetch** is enabled. - **--httpd=**\[*address***:**\]*port* Enable the Phi interface (HTTP server) on the specified address and port. The address is optional. - **--telnet=***port* Enable the Telnet interface on the specified port. - **--jpg-httpd=***port* Enable the screenshot HTTP server interface on the specified port. **This** **option is deprecated: use the Phi interface instead.** - **--enable-terrasync**, **--disable-terrasync** Enable/disable automatic scenery/object downloads. - **--terrasync-dir=***directory* Set the directory where the downloaded scenery will be stored to *directory*. - **--enable-fgcom**, **--disable-fgcom** Enable/disable the FGCom (voice ATC) integration. ### I/O options - **--generic=***params*, **--atlas=***params*, **--atcsim=***params*, **--AV400=***params*, **--AV400Sim=***params*, **--AV400WSimA=***params*, **--AV400WSimB=***params*, **--garmin=***params*, **--hla=***params*, **--hla-local=***params*, **--igc=***params*, **--joyclient=***params*, **--jsclient=***params*, **--native-ctrls=***params*, **--native-gui=***params*, **--native-fdm=***params*, **--native=***params*, **--nmea=***params*, **--opengc=***params*, **--props=***params*, **--pve=***params*, **--ray=***params*, **--rul=***params* Open a connection to drive external programs or hardware. Specify the protocol by using the correct command-line option: - • **generic**: a predefined communication interface and a preselected communication protocol; - • **atlas**: the Atlas protocol; - • **atcsim**: the ATCsim (atc610x) protocol; - • **AV400**: the Garmin AV400 protocol, required to drive a Garmin 196/296 series GPS; - • **AV400Sim**: the set of AV400 strings required to drive a Garmin 400-series GPS; - • **AV400WSimA**, **AV400WSimB**: the set of strings required to drive a Garmin WAAS GPS (where the **A** channel uses a variant of the AVSim400 protocol and the **B** channel communicates with the GPS unit); - • **garmin**: the Garmin GPS protocol; - • **hla**, **hla-local**: the HLA protocol, either remote or local; - • **igc**: the International Glider Commission protocol; - • **joyclient**: the protocol used by Agwagon joysticks; - • **native-ctrls**: the FlightGear Native Controls protocol; - • **native-gui**: the FlightGear Native GUI protocol; - • **native-fdm**: the FlightGear Native FDM protocol; - • **native**: the FlightGear Native protocol; - • **nmea**: the NMEA protocol (used to drive most GPS units); - • **opengc**: the protocol used by OpenGC, a software used to render high-quality glass cockpit displays for simulated flightdecks; - • **props**: the interactive property manager protocol; - • **pve**: the PVE protocol; - • **ray**: the Ray Woodworth motion chair protocol; - • **rul**: the RUL protocol. The parameters (*params*) must be in the form *medium***,***direction***,***hz***,***medium\_options* where *medium* is the medium used by the protocol (**serial**, **socket**, **file**...), *direction* is the communication direction (**in**, **out** or **bi**), *hz* is the frequency the channel should be processed at (floating point values are accepted) and *medium\_options* are: - • for serial protocols, *device***,***baud*, where *device* is the device name to be opened and *baud* is the communication baud rate; - • for socket protocols, *machine***,***port***,***style*, where *machine* is the machine name or the IP address of the server (if the simulator should act as a client) or is left empty (if the simulator should act as a server), *port* is the port to use (or is left empty to ask the operating system to choose an available port) and *style* is **tcp** or **udp**; - • for file protocols, *filename*, where *filename* is the name of the file data should be written to. ### Debugging options - **--enable-fpe** Abort when a floating-point exception is encountered. - **--fgviewer** View the scenery and the aircraft in a simple model viewer, without loading the entire simulator. - **--log-level=bulk**\|**debug**\|**info**\|**warn**\|**alert** Set the minimum logging level. Log messages having a severity greater than or equal to the specified value are recorded; the others are discarded. - **--log-class=all**\|**none**\|**ai**\|**environment**\|**flight**\|**general**\|**io**\|**network**\|**sound**\|**terrain**\|... Log only events belonging to the specified log classes (**all** logs all events, **none** logs none). Multiple classes can be specified by separating them with commas or pipes, for example: **--log-class=ai,flight**. - **--log-dir=***dir* Save the logs in the directory *dir*. If *dir* is **desktop**, the logs are saved on the Desktop. This option may be given several times, using a different directory each time. Inside the specified directory, the log file will be named *FlightGear\_*YYYY*-*MM*-*DD*\_*num*.log*, where *YYYY-MM-DD* is the current date and *num* is a progressive number starting at **0**. - **--trace-read=***property*, **--trace-write=***property* Trace the reads/writes for a property (print a log message whenever *property* is read from/written to). - **--developer** Enable developer mode. ## EXIT STATUS **fgfs** exits with **0** if the execution completes successfully, or with another status (usually **1** or **-1**) if an error occurred. ## ENVIRONMENT - **COMPUTERNAME** Specifies the hostname of the system in use. This environment variable is only taken into account on Microsoft Windows operating systems. - **FG\_AIRCRAFT** Specifies the path in which aircraft should be searched for. - **FG\_LAUNCHER** If this environment variable is set and is not **0**, the Qt launcher will be shown. The variable is mainly used on Mac OS X operating systems to avoid the use of wrapper scripts. - **FG\_ROOT** Specifies the root data directory to use. - **FG\_SCENERY** Specifies the scenery directory to use. - **HTTP\_PROXY** Specifies the HTTP proxy to use. Must be in the form **http://host:port/**. - **LANG** Specifies the language to use. ## FILES - *~/.fgfs* The main directory where FlightGear configuration files and data (downloaded aircraft/scenery) are stored. - *~/.fgfsrc.hostname*, *~/.fgfsrc* Configuration files containing command-line options for [**fgfs**(1)](/fgfs/1.md).