username field empty

[quentinhardy]

Hello,

When I use the following python code as an administrator on windows, some usernames are empty:

>> run pyshell 
>>> import sys
>>> print (sys.version)
2.7.11 (v2.7.11:6d1b6a68f775, Dec  5 2015, 20:32:19) [MSC v.1500 32 bit (Intel)]
>> import psutil
>>> print psutil.__version__
4.1.0
>>> for proc in psutil.process_iter():print proc.as_dict(attrs=['username', 'pid', 'name', 'exe', 'cmdline', 'status'])
[...]
{'username': 'NT AUTHORITY\\SYSTEM', 'status': 'running', 'exe': None, 'name': 'System Idle Process', 'pid': 0, 'cmdline': []}
{'username': 'NT AUTHORITY\\SYSTEM', 'status': 'running', 'exe': None, 'name': 'System', 'pid': 4, 'cmdline': []}
{'username': None, 'status': 'running', 'exe': None, 'name': 'smss.exe', 'pid': 252, 'cmdline': None}
[...]

Notice the username of the smss.exe process (i.e. System) is empty.

If I use the following powershell code as an administrator, I see all usernames:

$owners = @{}
gwmi win32_process |% {$owners[$_.handle] = $_.getowner().user}
get-process | select processname,Id,@{l="Owner";e={$owners[$_.id.tostring()]}}

ProcessName                                        Id Owner                    
-----------                                        -- -----                    
[...]             
services                                          428 Système                  
smss                                              252 Système                  
spoolsv                                          1244 Système                  
[...]

Why I can't see usernames (e.g SYSTEM) of some processes with psutil.process_iter() while I can with powershell for example?

Thank you in advance for your help,

[giampaolo]

So Process.as_dict() method sets None for any "field" it is unable to determine due to permission errors so it is very likely that if you'd use Process.username() method directly you will see the actual AccessDenied exception being raised and unfortunately there's nothing you can do about that.
Power shell is able to do that because it uses the WMI interface, which has no such (permission) limitation.