who

who linux command cheatsheet by Thamizhiniyan C S

Introduction

This command is used to show who is logged on.

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Syntax

who [OPTION]... [ FILE | ARG1 ARG2 ]

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Important Flags

Flag	Description
-a, --all	Print all information provided by -b, -d, --login, -p, -r, -t, -T, -u options.
-b, --boot	Display the time of the last system boot.
-d, --dead	Print dead processes.
-H, --heading	Print a line of column headings.
--ips	Print IPs 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	Display only hostname and user associated with stdin.
-p, --process	Print active processes spawned by init.
-q, --count	Print all login names and the number of users logged on.
-r, --runlevel	Print the current runlevel.
-s, --short	Print only name, line, and time (default).
-t, --time	Print the last system clock change.
-T, -w, --mesg	Add user's message status as +, - or ?.
-u, --users	List users logged in.
--message	Same as -T.
--writable	Same as -T.
--help	Display help information and exit.
--version	Output version information and exit.

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Examples

Command	Description
who	Display a list of the logged-in usernames.
who -s	Achieve the same effect as 'who' with the short format.
who -H	Print column headers above the list of users.
who -m	Display information about the current user only.
who -l	Show a list of available terminals.
who -b	Display the time of the last system boot.
who -q	List the usernames and the number of users currently logged on.
who -T	Show the user's message status.
who -p	Print a list of active processes spawned by init.
who -d	Print a list of dead processes.
who -r	Display the current runlevel of the system.
who -t	Print the last time the system clock was changed.
who -u	Show how long each user has been idle.
who -a	Print all information provided by various options in a single output.