Linux in a Nutshell, Fourth Edition

Name

who

Synopsis

                  who [options] [file]
who am i
               

Show who is logged into the system. With no options, list the names of users currently logged in, their terminal, the time they have been logged in, and the name of the host from which they have logged in. An optional system file (default is /etc/utmp) can be supplied to give additional information.

Options

am i

Print the username of the invoking user.

--help

Print a help message and then exit.

-i, -u, --idle

Include idle times. An idle time of . indicates activity within the last minute; one of old indicates no activity in more than a day.

-l, --lookup

Attempt to include canonical hostnames via DNS.

-m

Same as who am i.

-q, --count

“Quick.” Display only the usernames and total number of users.

--version

Print version information and then exit.

-w, -T, --mesg, --message, --writable

Include user’s message status in the output:

+

mesg y (write messages allowed)

-

mesg n (write messages refused)

?

Cannot find terminal device

-H, --heading

Print headings.

Example

This sample output was produced at 8 a.m. on April 17:

$ who -uH
NAME    LINE   TIME         IDLE   PID  COMMENTS
Earvin  ttyp3  Apr 16 08:14 16:25  2240
Larry   ttyp0  Apr 17 07:33   .   15182

Since Earvin has been idle since yesterday afternoon (16 hours), it appears that he isn’t at work yet. He simply left himself logged in. Larry’s terminal is currently in use.