python - execute shell command with DISPLAY specified?

Question

I read through a lot of the answers but can't figure out how to execute a command which I currently execute using cron from subprocess or something better?

# cron command
00 16 * * 1-5 DISPLAY=:10 /path/to/shell/script.sh > log/file.log 2>&1

The DISPLAY is Xvfb.

Use os.env to set the environment variable, then use subprocess.Popen() to run the script. — Barmar
– Barmar, Commented Nov 8, 2022 at 16:24
@Barmar how would I go about doing that? The DISPLAY=:10 is initiated. I tried checking os.env() but got a >AttributeError: module 'os' has no attribute 'env' — Sid
– Sid, Commented Nov 8, 2022 at 16:29
Sorry, it's os.environ. So os.environ['DISPLAY'] = ':10' — Barmar
– Barmar, Commented Nov 8, 2022 at 16:29

Barmar · Accepted Answer · 2022-11-08 16:33:49Z

1

Set the environment variable using os.environ, then run the command using the subprocess module.

import subprocess
import os

os.environ['DISPLAY'] = ':10'
with open('log/file.log') as out:
    subprocess.Popen(['/path/to/shell/script.sh'], stdout=out, stderr=subprocess.STDOUT)

answered Nov 8, 2022 at 16:33

Barmar

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3 Comments

Barmar Over a year ago

That's true, but unless the Python script is using the DISPLAY environment variable for other things, it probably doesn't matter.

Sid Over a year ago

There are mutliple scripts being run using cron which are utilizing the DISPLAY. I am not sure if this affects the code though. I am getting a >Error: process is already running.

Barmar Over a year ago

That's an unrelated issue. If script.sh only allows itself to be run once, you can't run it from both cron and from your Python script at the same time. It has nothing to do with DISPLAY.

Charles Duffy · Accepted Answer · 2022-11-08 18:49:04Z

0

Using the env= argument to subprocess.Popen, you can change the environment only for the child process, without modifying the environment of the Python process itself:

import subprocess
import os

with open('log/file.log') as out:
    subprocess.Popen(['/path/to/shell/script.sh'],
                     env=dict(os.environ, DISPLAY=":10"),
                     stdout=out, stderr=subprocess.STDOUT)

edited Nov 8, 2022 at 18:49

answered Nov 8, 2022 at 16:41

Charles Duffy

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4 Comments

Sid Over a year ago

I get an TypeError: unsupported operand type(s) for |: 'dict' and 'dict'. Its from the env=(dict(os.environ) | {"DISPLAY": ":10"}) trying to fix it.

Charles Duffy Over a year ago

Which version of Python? Works fine on 3.9

Sid Over a year ago

Oh, I am using: 3.6.9

Charles Duffy Over a year ago

@Sid, how about env=dict(os.environ, DISPLAY=":10")?

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