Linux service and saving logs into a file

Question

Using RPi, I am sending and receiving data to and from ESP32 at the same time. I have two .py scripts and two linux services. Before I created the services the .py scripts were working correctly (but not at the same time, thats why I am making services), the rec_data.log contained data from ESP32.

They work in parallel (checked via systemctl status for both services), also ESP32 is getting the message from RPi. But the part with saving data from ESP into a .log file on RPi is not working.

I used StandardOutput=... and the rec_data.log file is getting created, but remains empty. It should get a "TEST" string per 5 seconds.

My receive.service looks as follow:

[Unit]
Description=Test Service
#After=multi-user.target
#[email protected]

[Service]
#Type=simple
ExecStart=/usr/bin/python3 /home/pi/receive.py
StandardOutput=append:/home/pi/rec_data.log # tried without these two lines also (didnt work)
StandardError=append:/home/pi/rec_err.log # tried without these two lines also (didnt work)
#Restart=always
#StandardInput=tty-force

[Install]
WantedBy=multi-user.target

My receive.py script looks as follow:

from bluetooth import *
file = open("rec_data.log", "a") // tried to give the full path to the file also (didnt work)
def rx_and_echo():
    while True:
        data1 = sock.recv(buf_size)
        if data1:
            data1 = str(data1)
            data1 = data1[2:-1]
            file.write(data1 + '\n')

addr = "E0:E2:E6:CF:BB:AA"
service_matches = find_service(address=addr)
buf_size = 1024

if len(service_matches) == 0:
    print("couldn't find the SampleServer service =(")
    sys.exit(0)

first_match = service_matches[0] 
port = first_match["port"]
name = first_match["name"]
host = first_match["host"]

port = 1 
sock = BluetoothSocket(RFCOMM)
#sock.connect((host, port)) // this is done on send.py so cannot be doubled here

rx_and_echo()
file.close()
sock.close()

Answer 1

You are mixing two concept here.

1. you want to write to a file explicitly in python
2. you want to redirect the standard output to the same file.

I think also that you problem could come from the python buffering.

Keep the .service file and try this:

• use print instead of file.write
• flush after a write

---

import sys
from bluetooth import *
def rx_and_echo():
    while True:
        data1 = sock.recv(buf_size)
        if data1:
            data1 = str(data1)
            data1 = data1[2:-1]
            print(data1)
            sys.stdout.flush()

addr = "E0:E2:E6:CF:BB:AA"
service_matches = find_service(address=addr)
buf_size = 1024

if len(service_matches) == 0:
    print("couldn't find the SampleServer service =(")
    sys.exit(0)

print('connected')

first_match = service_matches[0] 
port = first_match["port"]
name = first_match["name"]
host = first_match["host"]

port = 1 
sock = BluetoothSocket(RFCOMM)
#sock.connect((host, port)) // this is done on send.py so cannot be doubled here

rx_and_echo()
sock.close()