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I'm developing a Django app which runs Matlab scripts with Python's Popen class. The python script that calls Matlab scripts lives in the main folder of my Django app (with views.py). When I call the script from command line, it runs like a charm but when I make a request from the client in order to run the corresponding python script, I receive the following warning:

My app uses a Python virtual environment and it is being deployed with Apache web server. Here is my python script that calls Matlab scripts:

import os
import subprocess as sp
import pymat_config
def pymat_run():
    pwd = pymat_config.pwd_config['pwd']
    cmd1 = "-r \"Arg_in = '/path/to/my/main/folder/input.txt'; Arg_out = '/path/to/my/main/folder/file.txt';  matlab_script1\""
    baseCmd1 = ['/usr/local/MATLAB/R2018a/bin/matlab', '-nodesktop', '-nosplash', '-nodisplay', 'nojvm', cmd1]
    os.chdir('/path/to/matlab_script1')
    sudo_cmd = sp.Popen(['echo', pwd], stdout=sp.PIPE)
    exec1 = sp.Popen(['sudo', '-S'] + baseCmd1, stdin=sudo_cmd.stdout, stdout=sp.PIPE, stderr=sp.PIPE)
    out, err = exec1.communicate()
    return out
Any suggestions ?
                Looks like Matlab can't start up because the server doesn't have write access to the Matlab preferences file.  I don't have time to try things out right now, but you might try setting MATLAB_PREFDIR in your server env to an existing writable directory?
– RishiG
                Oct 26, 2018 at 18:48
                @RishiG thank you for your response. Finally the issue was that I was calling the script as a "user" and not as a web-server's user. I posted my answer below.
– Capdi
                Oct 27, 2018 at 8:58
Finally I managed to find the solution of that issue by myself. The problem came from the kind of user who called the Matlab's script. When I was running the above script from a Python interpreter or from the shell, it was the user (with the user password) who was running the script while when I was calling the script from the client the user was the web server's user: www-data.
So at first to avoid the above warning I gave permissions to www-data user to the /var/www folder with the following command:
sudo chown -R www-data /var/www/
After that, the "Warning" disappeared but the script still didn't run because it was asking for www-data's password internally and taking user's password from pymat_config file.
To solve this, I edited /etc/sudoers file in order for www-data to be able to call Matlab scripts without asking password. So I added the following line:
www-data ALL=(ALL) NOPASSWD: /usr/local/MATLAB/R2018a/bin/matlab
and now it runs like a charm !
        
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