Adriano Ferreira wrote:
> Etc.getlogin likely "implements the C library function of the
> same name, which on most systems returns the current login
> from /etc/utmp, if any". 
> 
> With a 'su' you changed the real user user id and getlogin() returns
> the name associated with the current login activity. So as Guy Decoux
> said it is the expected behaviour and
>         Etc.getpwuid(Process::Sys.geteuid)[:dir]
> is what you want.
> 

Ok, now I see. 'su -', according to man page, should ``Simulate a full 
login.''. On the other hand, 'getlogin', according to 'Linux 
Programmer's Manual', ``returns  a pointer to a string containing the 
name of the user logged in on the controlling terminal of the process''.

'NetBSD System Calls Manual' is explicit about this behaviour:
``The name is normally associated with a login shell at the time a 
session is created, and is inherited by all processes descended from the 
login shell.  (This is true even if some of those processes assume 
another user ID, for example when su(1) is used.)''

Thanks for your help, guys, and sorry for the noise.

r.