Linux who command

Updated: 05/04/2019 by Computer Hope
who command

On Unix-like operating systems, the who command displays users logged in to the system.

This document covers the GNU/Linux version of who.

Description

The who command prints information about all users who are currently logged in.

Syntax

who [ OPTION ]... [ FILE ] [ am i ]

Options

-a, --all Same as using the options -b -d --login -p -r -t -T -u.
-b, --boot Display the time of the last system boot.
-d, --dead Display dead processes.
-H, --heading Print a line of column headings.
--ips Print IP addresses instead of hostnames. With --lookup, canonicalizes based on stored IP, if available, rather than stored hostname.
-l, --login Print system login processes.
--lookup Attempt to canonicalize hostnames via DNS.
-m Only print information about the user and host associated with standard input (the terminal where the command was issued). This method adheres to the POSIX standard.
-p, --process Print active processes spawned by init.
-q, --count Displays all login names, and a count of all logged-on users.
-r, --runlevel Print the current runlevel.
-s, --short Print only name, line, and time fields, which is the default.
-t, --time Print the last time the system clock was changed, if the information is available.
-T, -w, --mesg Add a character which indicates the state of the terminal line: "+" if the terminal is writable, "-" if it is not, or "?" if a bad line is encountered.
-u, --users Print the idle time for each user, and the process ID.
--message Same as -T.
--writable Same as -T.
--help Display a help message, and exit.
--version Display version information, and exit.

Notes

If FILE is specified, who gathers its information from this file. Otherwise, it reads from a default file location (usually /var/run/utmp).

If the arguments "am i" are specified, who assumes the -m option.

Examples

who

Displays the username, line, and time of all currently logged-in sessions. For example:

who

who am i

Displays the same information, but only for the terminal session where the command was issued, for example:

alan     pts/3        2013-12-25 08:52 (:0.0)

who -aH

Displays "all" information, and headers above each column of data, for example:

NAME       LINE         TIME             IDLE          PID COMMENT  EXIT
                        2014-01-17 07:00               154 id=si    term=0 exit=0
           system boot  2014-01-17 07:00
           run-level 2  2014-01-17 07:00                   last=S
                        2014-01-17 07:01              1607 id=l2    term=0 exit=0
LOGIN      tty6         2014-01-17 07:01              2809 id=6
LOGIN      tty5         2014-01-17 07:01              2808 id=5
LOGIN      tty4         2014-01-17 07:01              2807 id=4
LOGIN      tty2         2014-01-17 07:01              2805 id=2
LOGIN      tty1         2014-01-17 07:01              2804 id=1
LOGIN      tty3         2014-01-17 07:01              2806 id=3
           pts/0        2014-01-17 11:31              2811 id=ts/0  term=0 exit=0
lucy     + pts/1        2014-01-17 22:42   .          6609 (:0.0)
           pts/2        2014-01-18 02:14                 0 id=/2    term=0 exit=0
           pts/3        2014-01-18 02:08                 0 id=/3    term=0 exit=0
           pts/4        2014-01-17 21:30                 0 id=/4    term=0 exit=0
lucy     + pts/0        2014-01-17 22:01 01:04        6330 (:0.0)

date — Output the current date and time.
last — Display a listing of the most recently logged-in users.
login — Begin a session on a system.
mesg — Control if (non-root) users can send messages to your terminal.
su — Become the superuser or another user.
w — Show who is logged on and what they are doing.
whoami — Print your effective userid.