Score:2

Ubuntu

How can I launch a script in a terminal window from a service

Nareik Seivad

7/3/24, 2:09 AM

I have two scripts which together allow me to receive and answer phone calls over serial. The first is what I want to run as a service in the background it checks if there is a RING signal and if there is then open a terminal window with the second script running.

They both use python3, the first script is:

while True:
if (ser.inWaiting() > 0):
    x = ser.readline()
    if (x == b'RING\r\r\n'):
        os.system("gnome-terminal -- python3 /home/user/answer.py")
        exit()

The main part of the second is:

    os.system("clear")
    print("Incoming Call")
    PU = input("Press Enter To Pick Up")
    send_at('ATA' + ';','OK',1)
    os.system("clear")
    print("ON CALL")
    HU = input("Press Enter To Hang Up")
    send_at("AT+CHUP\r\n" + ';','OK',1)
    os.system("clear")
    print('Call Ended')
    time.sleep(3)
    os.system("clear")
    os.system("gnome-terminal -- python3 /home/user/ring.py")
    os.system("exit")

If I run the first in an open terminal just as "python3 ring.py" it works fine but leaves me with a constant open terminal.

What I want is to run Ring.py as a service or a background process that just launches Answer.py as it's called.

I tried using a .service file, enabled and started it, htop showed that it was running Ring.py but it wouldn't launch Answer.py in a terminal window. There's no error code it just doesn't show up.

This is the service file:

[Unit]
Description=Detect Incoming Calls

[Service]
Type=simple
User='my username'
ExecStart= /usr/bin/python3 /home/user/Ring.py
Restart=always

[Install]
WantedBy=multi-user.target

How can I get this to work the way I want? Or what am I doing wrong?

165

1 + 3

python

command-line

scripts

gnome-terminal

systemd

Raffa

7/3/24, 7:35 AM

Are you setting, enabling and starting that as user service e.g. `systemctl --user start service-name` to make use of the running graphical user session so the `gnome-terminal` can launch? ... A system service is not what you want.

Nareik Seivad

7/3/24, 8:04 AM

Yes... that is I think what I am attempting. Will a system service not launch a graphical gnome-terminal window with a script running in it? All I want is for the Ring.py to run invisible and launch Answer.py in a terminal window when it receives a call

Raffa

7/3/24, 9:25 AM

I added an answer with more explanation ... I hope its clear and helpful ... And you should avoid unneeded spaces around the equal `=` sign like `ExecStart= /usr/bin/python3 ...` should be `ExecStart=/usr/bin/python3 ...`

Score:2

Ubuntu

Raffa

7/3/24, 9:24 AM

gnome-terminal is a user GUI application and it requires a display server user session up and running first and then, the service launching it will require certain environment variables set and/or proper authentication/permissions granted.

You can specify those environment variables in a system service by for example setting the address to the display server, but that can change and you might need to set it again and there is more to launching a GUI user application from systemd than just specifying those variables, so this is not recommended and a user service is the way to go IMO.

Therefore, you need to setup your service as a user-service in order to interact with your user-session environment by default as the environment variables like $DISPLAY will be automatically inherited by a user service.

To do that you need to, first, place your unit/service file either under /usr/lib/systemd/user/ or under ~/.config/systemd/user/ in your user's home.

Then, inform systemd about it without needing to reboot like so:

systemctl --user daemon-reload

Then, enable and start and manage it with the --user flag and without sudo like so:

systemctl --user enable unit-name

And:

systemctl --user start unit-name

You will always need to use the --user flag to manage it from now on ... for example:

systemctl --user status unit-name

Or:

systemctl --user restart unit-name

Or:

systemctl --user stop unit-name

Notice:

You don't need to specify a user/group for the user service as it will run as your current logged-in user by default.

You might, also, want to change Restart=always to Restart=on-failure to avoid running multiple instances of your script if status reporting is not set from your script as it appears.

You might, as well, want to change WantedBy=multi-user.target under [Install] section to WantedBy=default.target or similar graphical user target.

+ 1

Nareik Seivad

7/5/24, 1:00 AM

Ahhh there we go! Thank you so much!

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: How can I launch a script in a terminal window from a service

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