--- name: "zerk" section: "1" platform: "linux" package: "gpsd" version: "3.27.5-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/zerk" --- # zerk(1) All purpose GREIS fitting ## NAME zerk - All purpose GREIS fitting ## OPTIONS **zerk** \[OPTIONS\] \[server\[:port\[:device\]\]\] **zerk** -h **zerk** -V ## DESCRIPTION **zerk** is an all purpose GREIS (GNSS Receiver External Interface Specification) fitting. If you do not have a Javad GPS that speaks the GREIS protocol then you can stop reading now. This tool operates with your Javad GPS at a very low level. To understand **zerk** you must first be familiar with your Javad GPS and the documentation for the GREIS protocol. *GREIS Guide* \. **zerk** can decode common GREIS messages, poll the GPS status, enable and disable GPS features, and send user-generated commands to the GPS. It can read GREIS messages from a file. It can read and write directly through a serial device, or through a running **gpsd** instance. **zerk** does not require root privileges, except maybe to access the serial port in direct mode. It will run fine as root. Running under sudo will cause loss of functionality. ## OPTIONS The program accepts the following options: - **-?**, **-h** Makes **zerk** print a usage message and exit. - **-c COMMAND** Send a text string to the GPS. Accepts one parameter, COMMAND, the command string to send to the GPS. The string is sent verbatim, except a newline is appended. - **-d OPTION** Disable an option in the GPS. Accepts one parameter, OPTION, the option to disable. **zerk** will exit after the GPS acknowledges the command, unless the **-W** is given. 4HZ Disable basic GREIS messages at 4Hz. The messages are: \[RT\], \[UO\], \[GT\], \[PV\], \[SG\], \[DP\], \[SI\], \[EL\], \[AZ\], \[EC\], \[SS\], and \[ET\] COMPASS Disable use of the COMPASS (BeiDou) constellation. CONS Disable use of all constellations. DEFMSG Disable the default message set (/dev/msg) at 1Hz. GALILEO Disable use of the GALILEO constellation. GLONASS Disable use of the GLONASS constellation. GPS Disable use of the GPS constellation. IPR Disable all Integer Pseudo Range messages. These are \[rx\], \[rc\], \[r1\], \[r2\], \[r3\], \[r5\], \[rl\]. IRNSS Disable use of the IRNSS constellation. NMEA Disable basic NMEA 4.1e messages at 4Hz. The messages are GBS, GGA, GSA, GST, GSV, RMC, VTG, and ZDA. QZSS Disable use of the QZSS constellation. SBAS Disable use of the SBAS constellation. SNR Disable all SNR messages, except \[EC\]. The messages disabled are: \[E1\], \[E2\], \[E3\], \[E5\], \[El\]. - **-e OPTION** Enable an option in the GPS. Accepts one parameter, OPTION, the option to enable. **zerk** will exit after the GPS acknowledges the command, unless the **-W** is given. **-e** accepts the same OPTIONs as **-d**, except the action is to enable the option. - **-f FILE** Connect to a file or device. Accepts one parameter, FILE, the file or device to open. Files are opened read-only. Character devices are opened read/write, unless the -r parameter is given. Requires the pyserial module. - **-O OAF** Load an Option Authorization File (OAF) into the GPS. Accepts one parameter, OAF, command file to read. The OAF is just a special case of a '.jpo' (GREIS command file). -O will send any valid .jpo file to the GPS. - **-p PRESET** Send a preset command the GPS. Accepts one parameter, PRESET, the name of the command to send. **zerk** will exit after the GPS acknowledges the command, unless the **-W** is given. COLDBOOT Coldboot the GPS. CONS Poll the enabled constellations. DM Disable all periodic GREIS messages. ID Poll the receiver ID. IPR Poll all Integer Pseudo Range messages. These are \[rx\], \[rc\], \[r1\], \[r2\], \[r3\], \[r5\], \[rl\]. OAF Poll all OAF options. RESET Reset (reboot) the GPS. SERIAL Poll receiver serial number. SNR Poll all Signal to Noise Ratio (SNR) messages. \[EC\], \[E1\], \[E2\], \[E3\], \[E5\], \[El\]. VENDOR Poll GPS vendor. VER Poll GPS version. - **-r** Read only. Do not send anything to the GPS. - **-R RAW** Save all raw data from the GPS into the file RAW. - **-S SPEED** Configure the GPS serial speed to SPEED bps. - **-s SPEED** Set local serial port speed to SPEED bps. Default 115,200 bps. - **-V** Print **zerk** version and exit. - **-v VERBOSITY** Set verbosity level to VERBOSITY. Verbosity can be from 0 (very quiet), to 4 (very noisy). Default 2. - **-W** Force waiting the entire wait time. No early exit for completion of **-d**, **-e** or **-p** command. - **-w WAIT** Wait for WAIT seconds before exiting. Will exit early on command completion of **-d**, **-e** or **-p** command, unless **-W** is given. Default 2.0 second. ## ARGUMENTS By default, clients collect data from the local **gpsd** daemon running on localhost, using the default GPSD port 2947. The optional argument to any client may override this behavior: **\[server\[:port\[:device\]\]\]** For further explanation, and examples, see the **ARGUMENTS** section in the [**gps**(1)](/gps/1.md) man page ## ENVIRONMENT Options can be placed in the ZERKOPTS environment variable. ZERKOPTS is processed before the CLI options. ## EXAMPLES Print current Javad serial port of GPS connected to local running **gpsd**: ``` zerk -c "print,/cur/term" ``` Decode raw log file: ``` zerk -r -f greis-binary.log -v 2 ``` Change GPS port speed of device on /dev/ttyAMA0 to 230,400 bps: ``` zerk -S 230400 -f /dev/ttyAMA0 ``` Watch entire GPS reset cycle: ``` zerk -p RESET -v 2 -w 20 -W ``` Poll SVs Status: ``` zerk -W -w 2 -v 2 -c "out,,jps/{CS,ES,GS,Is,WS,QS}" ``` Dump **gpsd** data from remote server: ``` zerk -v 2 -w 5 server ``` ## RETURN VALUES **0** on success. **1** on failure ## SEE ALSO **zerk** is written to conform to the official Javad documentation for the GREIS protocol. *GREIS Guide* \. [**gpsd**(8)](/gpsd/8.md) ## RESOURCES **Project web site:** \ ## COPYING This file is Copyright 2013 by the GPSD project\ SPDX-License-Identifier: BSD-2-clause ## AUTHOR Gary E. Miller