ERROR: Failed to open interactive motion file.

[shinan6]

Hello! I've been trying to implement this project but seem to be stuck onto this point:
root@raspberrypi:/home/pi/bin# ./walb.sh
mkfifo: cannot create fifo ‘/tmp/fifo’: File exists
/tmp/latlon.txt
ERROR: Failed to open interactive motion file.
I followed the instructions step by step, but perhaps there's still something wrong and prevents me from success. The following is my .shfile, maybe you can point out the faults:
#!/bin/sh
SAMPLE=2048000
POWER=0
BRDC=brdc0240.17n
N_SAT=16
FIFO=/tmp/fifo
INT_FILE=/tmp/latlon.txt
DATE=2017/01/24,23:53:01
mkfifo $FIFO
./gps-sdr-sim -s $SAMPLE -e $BRDC -i $INT_FILE -b8 -n $N_SAT -o $FIFO -T $DATE&
hackrf_transfer -t $FIFO -f $FREQ -s $SAMPLE -x $POWER >/dev/nul

What can I do to solve this? Thank you so much!

[crescentvenus]

First error should be corrected as follows.
if [ ! -e $FIFO ] ; then
mkfifo $FIFO
fi

To fix "ERROR: Failed to open interactive motion file.
You have to create a file as /tmp/LatLon.txt . The format of the file is like 12.34,123.45,100.
To create /tmp/LatLon.txt you can use scripts under the "webui" directory.