Dashboard, switch to start and stop python program

[KenjiRed]

I want to make a switch which python program starts running on Raspberry Pi when it is ON and stops running when it is OFF.
I took Dashboard-Switch, Function-Switch and 2 Exec nodes.
At Dashboard-Switch I set Boolean TRUE for ON and FALSE for OFF.
At Function-Switch, I set 2 output. One is "is true" and the other is "is false"
(For the above 2, I also tried with number '0' and '1' but the result is the same)
For one Exec connected to 1st Function-switch output (True), I entered "python xxx.py" so that it starts Python Program. For the other Exec node connected to other Function-Switch put (False), I enter "kill xxx.py.

On UI, when I slide switch to ON, its python program starts. When I slide to OFF, it restarts its python program instead of stopping.

Any idea the better way to do it?

Many thanks in advance for the help

[harelabb]

Your approach seems reasonable (I'm a beginner, and would do about the same way).
However, I suggest you check the return code and maybe periodically check that the program is actually running, and feed that info back to the dashboard.

[KenjiRed]

Thanks for the comment...
I used pkill -f -SIGINT xxxx.py.
xxx may be replaced with $(ps aux | grep python) which means to take all python program.. which I have not tried in Node Red Exec.
In fact, it worked in expected manner when I unchecked "msg.payload"... I do not know exact reason for it but it seems to be acting as noise for 2nd Exec.

[zenofmud]

You can also use the status node to watch the exec node and then grab the PID from it and store it in a flow variable. Then you can have another flow that gets the PID from the global variable and sends 'kill nnn' where nnn is the PID number. Here is a sample

[{"id":"8ad88889.20b7f","type":"status","z":"79bc540c.0c3a9c","name":"","scope":["1c178d10.4959cb"],"x":160,"y":700,"wires":[["cd2f612f.afab68"]]},{"id":"5321b564.d42b1c","type":"debug","z":"79bc540c.0c3a9c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","x":750,"y":700,"wires":[]},{"id":"cd2f612f.afab68","type":"change","z":"79bc540c.0c3a9c","name":"store PID in flow.pid","rules":[{"t":"change","p":"status.text","pt":"msg","from":"pid:","fromt":"str","to":"","tot":"str"},{"t":"set","p":"pid","pt":"flow","to":"status.text","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":360,"y":700,"wires":[["5321b564.d42b1c"]]},{"id":"dc93cf66.62994","type":"inject","z":"79bc540c.0c3a9c","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":160,"y":740,"wires":[["e96b79ce.607078"]]},{"id":"e96b79ce.607078","type":"change","z":"79bc540c.0c3a9c","name":"Build 'kill nnn' where nnn is the PID from flow.pid","rules":[{"t":"set","p":"payload","pt":"msg","to":"kill pid","tot":"str"},{"t":"change","p":"payload","pt":"msg","from":"pid","fromt":"str","to":"pid","tot":"flow"}],"action":"","property":"","from":"","to":"","reg":false,"x":450,"y":740,"wires":[["9a58e823.68f098"]]},{"id":"9a58e823.68f098","type":"exec","z":"79bc540c.0c3a9c","command":"","addpay":true,"append":"","useSpawn":"false","timer":"","oldrc":false,"name":"","x":750,"y":740,"wires":[[],[],[]]}]

The funny thing is I just put this together earlier today.

[harelabb]

I played a bit with this because I may have use for it later.
I wanted to:

• Start and stop the python program from a switch
• See if the program is running
• See the output from the program
• See the status of the program when exited
• Not start multiple instances simultaneously

I ended up with this:

The code is at https://gist.github.com/harelabb/3d36f187f48274dbf5b880fcf51a138b

[harelabb]

Forgot: the python code I run is

#! /usr/bin/python
import subprocess as sp
for i in range(10):
    sp.call("date")
    sp.call(["sleep", "5"])

and the dashboard: