How to run and cancel a linux command using Flask Python API?

S Andrew 0
Viewed 18

I am working on flask based python api. It has two api, run_cmd and stop_cmd. Run cmd will execute a command in the terminal. This command will keep on going until someone manually cancels it. So to cancel it, we have stop_cmd api. Below is the code:

from flask import Flask, jsonify, request
from threading import Thread  
from subprocess import call 

app = Flask(__name__)

def RunCmd():
    call('while true; do echo "hello"; sleep 2s; done', shell=True)

@app.route('/run_cmd', methods=['GET'])
def run_cmd():
    Thread(target=RunCmd).start()
    return jsonify({"status": "ok"}), 200

@app.route('/stop_cmd', methods=['GET'])
def stop_cmd():
    # This api will stop the cmd running in RunCmd

As you can see in the above code, if we hit the /run_cmd, it starts and keeps printing hello in the terminal. I wanted to know how can we cancel this ongoing session of the command so that we can write it in stop cmd api. Is this possible. Thanks

multithreading subprocess flask api python-3.x
2 Answers

This is how I solved it

from flask import Flask, jsonify, request
from threading import Thread  
import subprocess
import psutil
from subprocess import call 
from command_runner import command_runner


app = Flask(__name__)

proc = ""

def kill(proc_pid):
    process = psutil.Process(proc_pid)
    for proc in process.children(recursive=True):
        proc.kill()
    process.kill()

def RunCmd():
    global proc
    proc = subprocess.Popen(['while true; do echo "hello"; sleep 2s; done'], shell=True)
    

@app.route('/run_cmd', methods=['GET'])
def run_cmd():
    Thread(target=RunCmd).start()
    return jsonify({"status": "ok"}), 200

@app.route('/stop_cmd', methods=['GET'])
def stop_cmd():
    global proc
    kill(proc.pid)
    return jsonify({"status": True}), 200


if __name__ == '__main__':
    app.run(host='127.0.0.1', port=5000)
S Andrew0

Subprocess.call is a part of an older, deprecated API if I am informed correctly. Instead, you should probably use subprocess.Popen(). Then you could start your command by running

proc = subprocess.Popen(["somecommand", "-somearg", "somethingelse"])

This will return a Popen object which you can terminate by sending it a signal, for example proc.terminate() or proc.kill().

Gasp0de0
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