You've got the following two ways to create your account from command line:
geth account new --password <(echo $mypassword)
geth account new --password [arg]
[arg] = the name of a file containing the password and not the password itself.
One more way is to start your network in one window of PowerShell (in windows) and then, in a new PowerShell window, execute the folllowing command:
and then use management APIs