Im trying to readout the data from my ublox LEA-6H recever over RTKLIB's str2str command-line user interface (CUI). Im using rtkkib_2.4.2 on ubuntu 16.04.02 and the ublox receiver is connected over usb. im trying the following

sudo ./str2str -in serial://ttyUSB0:38400#ubx –out file://~/test.txt#ubx

i get the errormsg:

specify output stream(s)

how can i understand the documentation of rtklib. it says the following: rtklib2.4.2-doc

1 Answer 1


Your shell is possibly interpreting the hashes in your command as comments. This might work better:

./str2str -in 'serial://ttyUSB0:38400#ubx'  ...

Also - are you using the right device specification? Additionally, using ~ with sudo might be problematic. Add yourself to the dialout group (or whatever group /dev/ttyUSB0 belongs to) so you can access the serial port without elevated privileges.

  • Checked if i'm a member of dialout and tried: sudo ./str2str -in 'file:///dev/ttyUSB0:38400#ubx' –out 'file:///home/user/testlog.ubx' but i'm getting still the same error
    – Rud Qertz
    Mar 18, 2017 at 13:33
  • 1
    why are you still using sudo? You don't need to if your user is a member of dialout. The file:// specifications look redundant, so how about: ./str2str -in 'serial:///dev/ttyUSB0:38400#ubx' -out ~/testlog.ubx
    – scruss
    Mar 18, 2017 at 13:38
  • it still throws: specify output stream(s)
    – Rud Qertz
    Mar 20, 2017 at 10:17
  • sounds like it's very picky with command type and order. Ask here: str2, and see if anyone else has repeated the problem here: RTKLIB
    – scruss
    Mar 21, 2017 at 1:17
  • Try ./str2str -in serial://ttyUSB0:38400#ubx –out /home/user/test.ubx Also maybe try cat /dev/ttyUSB0 to test you have working permissions. I use a line like this in a script: str2str -in serial://ttyACM0:230400#ubx -out /home/pi/GPS/log/rover.ubx -out tcpsvr://:1888 -c /home/pi/GPS/m8t_5hz_usb.cmd
    – Dave X
    Dec 20, 2017 at 2:18

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