who

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

Syntax

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

Options	Description
-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's 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.

examples

who am i

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

who -aH

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