Using sudo to write to a file as root from a python script

Question

I'm trying to write a python script that writes some content to a file root through sudo, but it's not working at all. I am using:

 channel = 'stable'
 config_file = '/opt/ldg/etc/channel.conf'
 command = ['echo', '-n', channel, '|', 'sudo', 'tee', config_file]
 p = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
 out, _ = p.communicate()

But it seems as if this isn't doing anything.

I just want to write the contents of the variable channel to the file /opt/ldg/etc/channel.conf. But whatever I try just doesn't work. Can anyone offer any pointers?

Answer 1

sudo doesn't work like this. It doesn't read from standard input. You need to supply the command as an argument to sudo. Get the sudo syntax correct by learning to use it in a shell (eg terminal running bash )
before trying to use it from python code. Also, I think that passing the pipe character '|' as an argument to Popen is not the correct way to use pipes.

So, if you figure out how to use sudo without '|' you will solve both these issues.

Comments

Or try to change the permissions

os.system("chmod 666 config_file)

do what you want with the file and set the permissions back to their  original state.

Answer 2

Do you find anything with:

$ grep sudo /var/log/auth.log
(you may need to specify a different log)

Is the process that's trying to use the sudo command allowed to do so without a password?

man sudoers

Note - after editing /etc/sudoers you must set the permissions back to 440