Unexpected output when searching for a string from os.popen output

[FujiJean]

Hello Community,

on a Linux system I try to use nc command within a Python script to check if a UDP port is open or not.

My script:

import os
import re

CHECK = 0

UDPSTATUS = os.popen('nc -vz -u 127.0.0.1 123')
LINE = " "
while LINE:
        LINE = UDPSTATUS.read()
        print LINE
        if LINE.find('succeeded!') != -1:
           print " => UDP PORT OK"
           CHECK = 1
           print CHECK
UDPSTATUS.close()

if CHECK == 0:
        print " !!! UDP PORT NOT OK !!!"
        print CHECK

When the NTP service is running I got:

Output:
Connection to 127.0.0.1 123 port [udp/ntp] succeeded!

 !!! UDP PORT NOT OK !!!
0

I do not understand why the script does not find "succeeded!".
Can someone please explain why.

Best regards

[volcano63]

By default, subprocess APIs' output is bytestream. Use either

if LINE.find(b'succeeded!')

or

if LINE.decode().find('succeeded!')

or you may open the process with the argument universal_newlines=True - that will turn output format to text stream

[FujiJean]

Hello volcano63,

thank you for your reply.

I tested it but it did not work.

Meanwhile I have found a workaround. I write the result to a file and check the content of the file.
I got this to work so no need to inevstigate here further.

Best regards

[volcano63]

I tested it but it did not work.

Missed that you are on Python2 (why, oh, why?).