w

Show who is logged in and what they're doing

$ w

$ w -h

$ w [username]

$ w -s

$ w -i

w [-hisf] [user]

w displays information about currently logged-in users and their processes. The first line shows current time, system uptime, number of users, and load averages (same as uptime output).
Each subsequent line shows one logged-in user with their terminal, login time, idle time, CPU usage, and current activity. This gives a quick overview of system usage and user activity.
The "WHAT" column shows the current foreground process for each user, useful for seeing what people are running.
Idle time shows how long since the user's last terminal activity—useful for identifying inactive sessions.

-h, --no-header

Don't print the header line

Short format; don't print login time, JCPU, or PCPU

Toggle printing the FROM (remote host) field

Display IP addresses instead of hostnames

Old style output (space-separated)

Ignore username while calculating current process times

USER: Username
TTY: Terminal name
FROM: Remote host (or - for local)
LOGIN@: Login time
IDLE: Idle time
JCPU: Time used by all processes attached to tty
PCPU: Time used by current process
WHAT: Current process command line

The FROM field may be blank or show "-" for local logins or when hostname resolution fails.
CPU time columns (JCPU, PCPU) may not accurately reflect all activity, especially for background processes or when using terminal multiplexers.
Some processes may not appear in WHAT if they detach from the terminal.

who(1), uptime(1), users(1), last(1), finger(1)