subprocess stdout into a variable for Ngrok - python-3.x

Question

I'm trying to make a python script wich reports me the port on 0.tcp.ngrok.io is started when I run the code on terminal (after moving ngrok executable file to /usr/local/bin)
ngrok tcp 22
I get ths kind of output
ngrok by #inconshreveable (Ctrl+C to quit)
Session Status connecting
Version 2.2.4
Region United States (us)
Web Interface http://127.0.0.1:4041
Forwarding tcp://0.tcp.ngrok.io:13014 -> localhost:22
Connections ttl opn rt1 rt5 p50 p90
0 0 0.00 0.00 0.00 0.00
My first attempt is to log the subprocess stdout to a variable , but as the stdout is cyclic the stdout.read() never ends this is the code
import subprocess
ngrok = subprocess.Popen(['ngrok','tcp','22'],stdout = subprocess.PIPE)
output_text = ngrok.stdout.read() # script stops here forever
[**code for getting domain:port from output_text**]
how can I get a "snapshot" of stdout to a variable , without stoping ngrok?
Is there another way of doing this (next try would be a webscraper on localhost , but it would be nice to have this knowledge for other commands , such as "top")
thanks in advance

Answer 1

I had the same issue when I was working with ngrok http and all the alternatives weren't working, resulting in deadlocks and I even could print the child process response created with ngrok. Thus, reading the ngrok docs I notice that there is a way to get the ngrok public url with requests.
Adding the code below:
localhost_url = "http://localhost:4041/api/tunnels" #Url with tunnel details
tunnel_url = requests.get(localhost_url).text #Get the tunnel information
j = json.loads(tunnel_url)
tunnel_url = j['Tunnels'][0]['PublicUrl'] #Do the parsing of the get
So, tunnel_url will return what you need. Adding the imports the full code would be like this:
import subprocess
import requests
import json
ngrok = subprocess.Popen(['ngrok','tcp','22'],stdout = subprocess.PIPE)
localhost_url = "http://localhost:4041/api/tunnels" #Url with tunnel details
tunnel_url = requests.get(localhost_url).text #Get the tunnel information
j = json.loads(tunnel_url)
tunnel_url = j['Tunnels'][0]['PublicUrl'] #Do the parsing of the get

Answer 2

not enough reputation to comment, feel free to update or comment on #Rodolfo great answer and then delete this
Perhaps they've changed the api slightly, this is what worked for me:
(ngrok executable next to the script, serving http on port 5000 and picking the https tunneling url)
import subprocess
import requests
import json
import time
if __name__ == '__main__':
ngrok = subprocess.Popen(['./ngrok','http','5000'],
stdout=subprocess.PIPE)
time.sleep(3) # to allow the ngrok to fetch the url from the server
localhost_url = "http://localhost:4040/api/tunnels" #Url with tunnel details
tunnel_url = requests.get(localhost_url).text #Get the tunnel information
j = json.loads(tunnel_url)
tunnel_url = j['tunnels'][1]['public_url'] #Do the parsing of the get
print(tunnel_url)

Answer 3

This is working for me:
def open_tunnel():
process = subprocess.Popen(f'/snap/bin/ngrok tcp {PORT} --log "stdout"', shell=True, stdout=PIPE, stderr=PIPE) # You can also use a list and put shell = False
while True:
output = process.stdout.readline()
if not output and process.poll() is not None:
break
elif b'url=' in output:
output = output.decode()
output = output[output.index('url=tcp://') + 10 : -1]
return output.split(':')
I use /snap/bin/ngrok because my pycharm does not recognize path, sorry for that. You can replace it by saying only ngrok
.