开始一个新过程并读取该过程的输出

Question

I've got a python script reads data from a piped bash script

sudo beacon scan -b | get.py

I want to eliminate the use of bash piping and write everything in python. I'm trying to open a few processes in parallel to get my program to work the way I need it to. Process1 needs to start the 'sudo beacon scan -b' command and keep it running. Process2 needs to send that data to my servers. The last process needs to monitor if the process1 or process2 are working, and if not reboot them.

I've written process1 and process2.

process1:

#!/usr/bin/python
import subprocess
import multiprocessing

cmd = ['sudo', '/usr/local/bin/beacon', 'scan', '-b']
def scan():
   x = multiprocessing.Process(args=(subprocess.Popen(cmd)))
   x.start()
   x.join()

scan()

This runs the process correctly, but how do I get my second set of code the read the data from process1?

process2

import requests

for line in fileinput.input() #This needs to call the other process?
   if line.startswithh('ibeacon'):
      line = line.strip()
      a = line.split(' ')[1]
      a = line.split(' ')[2]
      a = line.split(' ')[3]
      a = line.split(' ')[4]
      a = line.split(' ')[5]
      payload = {'uuid': a, 'major': b, 'minor': c, 'power': d, 'rssi': e}
      r = requests.get('http://posttestserver.com/post.php', params=payload)

I don't know how to code process3 yet, but I need process1&2 to work first. How do I get process2 to read data from process1? I'm also getting an error from process1 saying the 'Popen' object is not iterable, but it still runs the 'beacon scan' command. Could this be because the 'beacon scan' command is constantly updating? Any advice would be helpful. I'm using Rasbian on a Raspberry Pi

Answer 1

The following code does what you want:

1) it runs a script as a subprocess. (I changed it to run "ping" for 3 seconds, for testing purposes.)

2) as each line is emitted from the subprocess, the parent proc handles it. In this case, it calls send_beacon() , transmitting some data to another server.

3) there is no #3. Profit!

source

import requests, subprocess

def send_beacon(line):
    if line.startswith('ibeacon'):
          line = line.strip()
          a = line.split(' ')[1]
          a = line.split(' ')[2]
          a = line.split(' ')[3]
          a = line.split(' ')[4]
          a = line.split(' ')[5]
          payload = {'uuid': a, 'major': b, 'minor': c, 'power': d, 'rssi': e}
          r = requests.get('http://posttestserver.com/post.php', params=payload)

if __name__=='__main__':
    if 0:
        cmd = ['sudo', '/usr/local/bin/beacon', 'scan', '-b']
    else:                       # testing
        cmd = 'ping -c3 8.8.8.8'.split()
    proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)
    for line in iter(proc.stdout.readline, ''):
        print 'X:',line,
        send_beacon(line)

output

X: PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
X: 64 bytes from 8.8.8.8: icmp_seq=1 ttl=43 time=46.9 ms
X: 64 bytes from 8.8.8.8: icmp_seq=2 ttl=43 time=94.5 ms
X: 64 bytes from 8.8.8.8: icmp_seq=3 ttl=43 time=48.1 ms
X: 
X: --- 8.8.8.8 ping statistics ---
X: 3 packets transmitted, 3 received, 0% packet loss, time 2002ms
X: rtt min/avg/max/mdev = 46.922/63.221/94.554/22.161 ms