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.
Equivalent to -b-d--login-p-r-t-T-u.
Print the username of the invoking user.
Print time of last system boot.
Print a list of dead processes.
Print a help message and then exit.
Include idle times. An idle time of . indicates activity within the last minute; one of old indicates no activity in more than a day.
Print list of system login processes.
Attempt to include canonical hostnames via DNS.
Same as who am i.
Print active processes spawned by init.
"Quick." Display only the usernames and total number of users.
Print the current runlevel.
Print only name, line, and time. This is the default behaviour.
Print the last system clock change.
Print a list of the users who are logged in.
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
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.