RTL_FM Pocsag Multimon decoder

#!/usr/bin/python
# working cmd:
# rtl_fm -f 153980000 -s 22050 -g 40 -p 65 | multimon-ng -a POCSAG1200 -f alpha -t raw -
'''

!! This requires a recent build of Multimon-NG as the old builds wont accept a piped input !!

Change the rtl_fm string to suit your needs.. add -a POCSAG512 , 2400 etc if needed to the Multimon-ng string
This just prints and writes to a file, you can put it in a threaded class and pass though a queue
or whatever suits your needs.


'''
import time
import sys
import subprocess
import os

def curtime():
    return time.strftime("%H:%M:%S %Y-%m-%d")

with open('error.txt','a') as file:
    file.write(('#' * 20) + '\n' + curtime() + '\n')

multimon_ng = subprocess.Popen("rtl_fm -f 153980000 -s 22050 -g 40 -p 65 | multimon-ng -a POCSAG1200 -f alpha -t raw -",
                               #stdin=rtl_fm.stdout,
                               stdout=subprocess.PIPE,
                               stderr=open('error.txt','a'),
                               shell=True)

try:
    while True:
        line = multimon_ng.stdout.readline()
        multimon_ng.poll()
        if line.__contains__("Alpha:"):    # filter out only the alpha
            if line.startswith('POCSAG'):
                address = line[22:28].replace(" ", "").zfill(7)
                message = line.split('Alpha:   ')[1].strip().rstrip('<ETB>').strip()
                output=(address+' '+curtime()+' '+ message+'\n')
                print address, curtime(), message
                with open('pocsag.txt','a') as f:
                    f.write(output)
        if not "Alpha:" in line:
            with open("missed.txt","a") as missed:
                missed.write(line + '\n')

except KeyboardInterrupt:
    os.kill(multimon_ng.pid, 9)