python
Python Daemon
There can only be one daemon process running: that is managed by the PID lock file, like most other Linux daemons. To stop it, do
kill `cat /var/run/eg_daemon.pid`
To see if it is running:
ps -elf | grep `cat /var/run/eg_daemon.pid`
Using the pidfile submodule, the PID file is managed automatically. When the daemon is stopped, the pidfile is cleared up. Please see the linked GitHub repo for the init script.
Here’s the Python daemon code:
#!/usr/bin/env python3.5
import sys
import os
import time
import argparse
import logging
import daemon
from daemon import pidfile
debug_p = False
def do_something(logf):
### This does the "work" of the daemon
logger = logging.getLogger('eg_daemon')
logger.setLevel(logging.INFO)
fh = logging.FileHandler(logf)
fh.setLevel(logging.INFO)
formatstr = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
formatter = logging.Formatter(formatstr)
fh.setFormatter(formatter)
logger.addHandler(fh)
while True:
logger.debug("this is a DEBUG message")
logger.info("this is an INFO message")
logger.error("this is an ERROR message")
time.sleep(5)
def start_daemon(pidf, logf):
### This launches the daemon in its context
### XXX pidfile is a context
with daemon.DaemonContext(
working_directory='/var/lib/eg_daemon',
umask=0o002,
pidfile=pidfile.TimeoutPIDLockFile(pidf),
) as context:
do_something(logf)
if __name__ == "__main__":
parser = argparse.ArgumentParser(description="Example daemon in Python")
parser.add_argument('-p', '--pid-file', default='/var/run/eg_daemon.pid')
parser.add_argument('-l', '--log-file', default='/var/log/eg_daemon.log')
args = parser.parse_args()
start_daemon(pidf=args.pid_file, logf=args.log_file)
For completeness’ sake, here is the init script. Note that “kill” is really just a method for sending a POSIX signal — see man page for signal(7) for an overview. The python-daemon context will catch the signal, terminate the process cleanly closing file descriptors, and delete the PID file automatically. So, it really is a clean termination.
You can write your code to catch SIGUSR1 or something similar, in order to do a reload of the daemon config. There is no advantage to writing Python stop the daemon.
#!/bin/bash
#
# eg_daemon Startup script for eg_daemon
#
# chkconfig: - 87 12
# description: eg_daemon is a dummy Python-based daemon
# config: /etc/eg_daemon/eg_daemon.conf
# config: /etc/sysconfig/eg_daemon
# pidfile: /var/run/eg_daemon.pid
#
### BEGIN INIT INFO
# Provides: eg_daemon
# Required-Start: $local_fs
# Required-Stop: $local_fs
# Short-Description: start and stop eg_daemon server
# Description: eg_daemon is a dummy Python-based daemon
### END INIT INFO
# Source function library.
. /etc/rc.d/init.d/functions
if [ -f /etc/sysconfig/eg_daemon ]; then
. /etc/sysconfig/eg_daemon
fi
eg_daemon=/var/lib/eg_daemon/eg_daemon.py
prog=eg_daemon
pidfile=${PIDFILE-/var/run/eg_daemon.pid}
logfile=${LOGFILE-/var/log/eg_daemon.log}
RETVAL=0
OPTIONS=""
start() {
echo -n $"Starting $prog: "
if [[ -f ${pidfile} ]] ; then
pid=$( cat $pidfile )
isrunning=$( ps -elf | grep $pid | grep $prog | grep -v grep )
if [[ -n ${isrunning} ]] ; then
echo $"$prog already running"
return 0
fi
fi
$eg_daemon -p $pidfile -l $logfile $OPTIONS
RETVAL=$?
[ $RETVAL = 0 ] && success || failure
echo
return $RETVAL
}
stop() {
if [[ -f ${pidfile} ]] ; then
pid=$( cat $pidfile )
isrunning=$( ps -elf | grep $pid | grep $prog | grep -v grep | awk '{print $4}' )
if [[ ${isrunning} -eq ${pid} ]] ; then
echo -n $"Stopping $prog: "
kill $pid
else
echo -n $"Stopping $prog: "
success
fi
RETVAL=$?
fi
echo
return $RETVAL
}
reload() {
echo -n $"Reloading $prog: "
echo
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
status)
status -p $pidfile $eg_daemon
RETVAL=$?
;;
restart)
stop
start
;;
force-reload|reload)
reload
;;
*)
echo $"Usage: $prog {start|stop|restart|force-reload|reload|status}"
RETVAL=2
esac
exit $RETVAL
ESP8266 WiFi module
Link for add board manager
http://arduino.esp8266.com/stable/package_esp8266com_index.json
Erase the esp
esptool.py erase_flash
Code to flash AT firmware to ESP8266 (ESP8266_AT_Bin_V1.5.1)
esptool.py --baud 115200 --port /dev/tty.wchusbserial1420 write_flash -fm dio -ff 40m -fs detect 0x00000 boot_v1.7.bin 0x01000 user1.1024.new.2.bin 0xfc000 esp_init_data_default.bin 0x7e000 blank.bin 0xfe000 blank.bin
Arduino and Python
If you want to read Arduino serial from Python.
Install pySerial:
pip intall pyserial
the code:
import serial ... print('# Arduino Reader - hackweb') print('entering loop...') ardu = serial.Serial('COM3', 115200) time.sleep(2) while True: print(ardu.readline())