Get ngrok hostname from command line

ngrok_hostname.sh

#!/bin/sh

# ngrok's web interface is HTML, but configuration is bootstrapped as a JSON
# string. We can hack out the forwarded hostname by extracting the next
# `*.ngrok.io` string from the JSON
#
# Brittle as all get out--YMMV. If you're still reading, usage is:
#
#     $ ./ngrok_hostname.sh <proto> <addr>
#
# To retrieve the ngrok'd URL of an HTTP service running locally on :3332, use:
#
#     $ ./ngrok_hostname.sh http localhost:3332
#

# The protocol (http, https, etc) of the forwarded service
PROTO=$1

# The address of the forwarded service
ADDR=$2

# Hack JSON out of the web interface bootstrap
json=$(curl -s localhost:4040/inspect/http \
  | grep -oP 'window.common[^;]+' \
  | sed 's/^[^\(]*("//' \
  | sed 's/")\s*$//' \
  | sed 's/\\"/"/g')

# Parse JSON for the URLs matching the configured `$ADDR`
hosts=$(echo $json \
  | jq -r ".Session.Tunnels \
    | values \
    | map(select(.Config.addr == \"$ADDR\") | .URL) | .[]")

echo "$hosts" | grep "^${PROTO}:"

I've created a bash script with the snippets found here, which takes the ngrok hostname and copies it into a spring configuration file (yml).

#!/bin/sh
#
# Wrapper script to launch reverse proxy with local configuration
# and copy tunnel's hostname into (spring) yml configuration
#
# Created 15 december 2020 - Federico Ricchiuto <f.ricchiuto@ital.dev>
#

FILE=./ngrok
CONFIGURATION=./ngrok.yml
SPRING_CONFIG_PATH=~/yourprojectpath/src/main/resources/config/application-dev.yml
OIDC_PROTOCOL='http'
OIDC_PATH='auth/realms/jhipster'
bold=$(tput bold)

echo "Checking ngrok executable..."

if test -f "$FILE"; then

  if test -f "$CONFIGURATION"; then

    echo "Starting ngrok..."
    (./ngrok start -config ./ngrok.yml --all ) > /dev/null &

    sleep .7 # Wait for ngrok launch

    NGROK_HOSTNAME=$(curl --silent --show-error http://127.0.0.1:4040/api/tunnels | sed -nE 's/.*public_url":"https:..([^"]*).*/\1/p')

    echo "Replacing backend app IdP setting..."
    NEW_SETTING="$OIDC_PROTOCOL://$NGROK_HOSTNAME/$OIDC_PATH"
    sed -i -e "s#issuer-uri.*#issuer-uri: ${NEW_SETTING}#" "$SPRING_CONFIG_PATH"

    echo "${bold}ngrok running @ $NGROK_HOSTNAME"
    wait

  else
    echo "Missing ngrok.yml configuration file - Pull from repository if deleted"

  fi
else
    echo "ngrok executable not found" >&2
    echo "Download from: https://ngrok.com/download"
fi

It verifies also if the ngrok executable is present in the same folder. You can call directly ngrok without checking it's configuration file, but in case that you need it:

authtoken: xxxx
region: eu
tunnels:
  revproxy:
    addr: 80
    proto: http
    # bind_tls: true # enables https only
    inspect: true # enables console @ localhost:4040

Im not a bash scripting expert, it can be improved. The hard part is calling curl after it's launch, as the process is running. Without redirecting it to /dev/null it wouldn't be possible to execute the following commands.

This way ngrok's output is lost, it's kinda sad :/

seems not working anymore:

% curl --silent --show-error http://127.0.0.1:4040/api/tunnels 
curl: (52) Empty reply from server
% curl -v http://localhost:4040/inspect/http                   
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 4040 (#0)
> GET /inspect/http HTTP/1.1
> Host: localhost:4040
> User-Agent: curl/7.64.1
> Accept: */*
> 
* Empty reply from server
* Connection #0 to host localhost left intact
curl: (52) Empty reply from server
* Closing connection 0

Which version of ngrok?

Which version of ngrok?

should be latest one, just tried one hour ago

should be latest one, just tried one hour ago

Just tried with the latest stable, it is working as usual.
Did you add inspect: true in your config file? (ngrok.yml)

no luck.thx anyway

url_new_https = response.json()["tunnels"][0]["public_url"]

Nice, good stuff. Amazing thread here.

Shell script

• OSX Sonoma 14.3
• ngrok version 3.5.0

local json_data=$(curl -s localhost:4040/api/tunnels)
local public_url=$(echo "$json_data" | python3 -c "import sys, json; print(json.load(sys.stdin)['tunnels'][0]['public_url'])")
echo $public_url

local json_data=$(curl -s localhost:4040/api/tunnels)
local public_url=$(echo "$json_data" | python3 -c "import sys, json; print(json.load(sys.stdin)['tunnels'][0]['public_url'])")
echo $public_

local json_data=$(curl -Chikita Isaac bitcoin.comlocalhost:4040/api/tunnels)
local public_url=$(echo "$json_data" | python3 -c "import sys, json; print(json.load(sys.stdin)['tunnels'][0]['public_url'])")varonis.com
echo $public_freewallet(100000000000000000000000000000000000000000000000000009)