CRON: Pyscreenshot all backends failed

[helpaohe]

Dear Community

I am trying to get a program from Vitor (https://stackoverflow.com/questions/578 ... attachment) to run every 15 minutes with crontab. The script works fine if I run it from the terminal with the following command

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sudo python /home/<username>/somepath/webscreen.py 

I then tried to get it to run with cron, but it simply didn't work. I made sure that cron works (and it does when using other scripts) and have used this troubleshooting guide (https://garyhall.org.uk/troubleshooting ... ry-pi.html). I got to point three and there I found the problem, however, I cannot solve it. Point three suggests to try if the "very limited" cron environment can run the job by running the following command:

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env -i /bin/bash --noprofile --norc

This command leads me to the bash-5.0$. If I then run the first mentioned command (running the script) in bash-5.0$, then I get the following error:

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bash-5.0$ sudo python /home/<username>/somepath/webscreen.py 
Traceback (most recent call last):
  File "/home/<username>/somepath/webscreen.py", line 44, in <module>
    main()
  File "/home/<username>/somepath/webscreen.py", line 39, in main
    imagem = ImageGrab.grab()
  File "/usr/local/lib/python2.7/dist-packages/pyscreenshot/__init__.py", line 31, in grab
    return backend_grab(backend, bbox, childprocess)
  File "/usr/local/lib/python2.7/dist-packages/pyscreenshot/loader.py", line 147, in backend_grab
    return auto(bbox, childprocess)
  File "/usr/local/lib/python2.7/dist-packages/pyscreenshot/loader.py", line 127, in auto
    raise FailedBackendError(msg)
pyscreenshot.err.FailedBackendError: All backends failed!

This is the python code which I am using (and which works if run from terminal with sudo priveliges):

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import smtplib
#from PIL import ImageGrab (does not work since only for mac / windows)
from email import encoders
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.image import MIMEImage
import os.path
import pyscreenshot as ImageGrab

def enviar_email():
    email = 'Someemail'
    password = 'Somepassword'
    subject = 'Info'
    message = 'Created by Vitor, edited by Marco'
    file_location = 'Some.jpg'

    msg = MIMEMultipart()
    msg['From'] = email
    msg['To'] = 'Someotheremail'
    msg['Subject'] = subject

    msg.attach(MIMEText(message, 'plain'))

    # Setup the attachment
    filename = os.path.basename(file_location)
    attachment = open(file_location, "rb").read()
    image = MIMEImage(attachment, name=filename)
    msg.attach(image)

    server = smtplib.SMTP('smtp.gmail.com', 587)
    server.starttls()
    server.login(email, password)
    text = msg.as_string()
    server.sendmail(email, email, text)
    server.quit()

def main():
    imagem = ImageGrab.grab()
    imagem.save('Stats.jpg', 'jpeg')
    enviar_email()

if __name__ == '__main__':
    main()

Since all permissions are correct and the script runs from terminal, there is definitely something wrong with cron which needs to be adjusted. Any ideas are welcome.

Best regards

[pcmanbob]

Any program run using cron is run in the background and no display/screen is linked to the running program , so I suspect that's why your program will not run from cron, there is not screen for pyscreenshot to take a shot of..

[geektechstuff.com]

pcmanbob's answer is probably correct, but out of curiosity you are running the Python with sudo, are you using the regular users crontab or the sudo crontab (i.e. crontab -e or sudo crontab -e)?