Cannot do "sudo su - postgres" with subprocess.call

Question

I try the following command:

subprocess.call(['sudo', 'su - postgres'], shell=True)

or

subprocess.call(['sudo', 'su', '-', 'postgres'], shell=True)

in Python2.7 (either by ipython manually writing the line, or python myfile.py being the line as part of the code), and get the sudo usage information:

usage: sudo [-D level] -h | -K | -k | -V
usage: sudo -v [-AknS] [-D level] [-g groupname|#gid] [-p prompt] [-u user
        name|#uid]
usage: sudo -l[l] [-AknS] [-D level] [-g groupname|#gid] [-p prompt] [-U user
        name] [-u user name|#uid] [-g groupname|#gid] [command]
usage: sudo [-AbEHknPS] [-C fd] [-D level] [-g groupname|#gid] [-p prompt] [-u
        user name|#uid] [-g groupname|#gid] [VAR=value] [-i|-s] [<command>]
usage: sudo -e [-AknS] [-C fd] [-D level] [-g groupname|#gid] [-p prompt] [-u
        user name|#uid] file ...

I can run the command in the shell with no problems at all. Both times it is the same shell.

Q: What am I doing wrong?

Wait. There are many other better ways to connect to postgres. Why are you using this? BTW to solve your problem you can do subprocess.call(['sudo su - postgres'], shell=True) — Bhargav Rao
– Bhargav Rao, Commented Jun 4, 2015 at 17:09

Zizouz212 · Accepted Answer · 2015-06-04 20:28:50Z

4

From the subprocess docs:

args is required for all calls and should be a string, or a sequence of program arguments. Providing a sequence of arguments is generally preferred, as it allows the module to take care of any required escaping and quoting of arguments (e.g. to permit spaces in file names). If passing a single string, either shell must be True (see below) or else the string must simply name the program to be executed without specifying any arguments.

Therefore, your list is really a sequence. For a single command, just place the string, together, as there is no need to have it split:

subprocess.call(['sudo su - postgres'], shell=True)

edited Jun 4, 2015 at 20:28

answered Jun 4, 2015 at 17:14

Zizouz212

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