Who's On? (Unix Power Tools, 3rd Edition)

2.8. Who's On?

The who command lists the users logged on to the system now. Here's an example of the output on my system:

% who
naylor   ttyZ1   Nov  6 08:25
hal      ttyp0   Oct 20 16:04   (zebra.ora.com:0.)
pmui     ttyp1   Nov  4 17:21   (dud.ora.com:0.0)
jpeek    ttyp2   Nov  5 23:08   (jpeek.com)
hal      ttyp3   Oct 28 15:43   (zebra.ora.com:0.)
    ...

Each line shows a different terminal or window. The columns show the username logged on, the tty (Section 2.7) number, the login time, and, if the user is coming in via a network (Section 1.21), you'll see their location (in parentheses). The user hal is logged on twice, for instance.

It's handy to search the output of who with grep (Section 13.1) -- especially on systems with a lot of users. For example:

% who | grep "^hal "             ...where is hal logged on?
% who | grep "Nov  6"            ...who logged on today?

-v Section 13.3

% who | grep -v "Nov  6"         ...who logged on before today?
    ...

The GNU who, on the CD-ROM [see http://examples.oreilly.com/upt3], has more features than some other versions.

-- JP