Documentation for who

_commands/basics/who.md

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+---
+---
+
+who
+---
+
+`who` provides information about logins and currently logged-in users.
+
+~~~ bash
+$ who 
+noahtutt tty7 	2018-10-21 11:46 (:0)
+$ who -b
+system boot 	2018-10-21 11:46
+$ who -r
+run-level 5	2018-10-21 11:46
+~~~
+
+<!--more-->
+
+### Useful Options 
+
+#### `who`
+With no arguments, who prints the name, shell location, time of login, and any comments for the current user. For users logged into a GUI shell, the commend field often contains the DISPLAY variable they are assigned to.
+
+~~~ bash
+$ who
+noahtutt	tty7		2018-10-21 11:46	(:0)
+~~~
+
+#### `who -H`
+Adds header information to the output of `who`. Can make the output easier to read or parse.
+
+~~~ bash
+$ who -H
+NAME		LINE		TIME			COMMENT
+noahtutt	tty7		2018-10-21 11:46	(:0)
+~~~
+
+#### `who -b`
+Prints time of the last system boot. Note that, while the system boot process is recorded, it doesn't have an owner name or a process ID.
+
+~~~ bash
+$ who -bH
+NAME		LINE		TIME			PID COMMENT
+		system boot	2018-10-21 11:46	
+~~~
+
+#### `who -r`
+Prints the current run-level of the operating system. 
+
+~~~ bash
+$ who -r
+		run-level 5	2018-10-21 11:46
+~~~ 
+
+The run-level of a Linux OS corresponds to a certain set of services that are expected to be running. Runlevel 5 corresponds to an operating system that is runninng in full multiuser mode with networking and a GUI (usually X windows) enabled.
+
+#### `who -u`
+Prints a list of all currently logged in users. Useful for collecting usage data for a machine with many users. When only one user is logged in, produces equivalent output to plain `who`
+
+~~~ bash
+$ who -u
+noahtutt	tty7		2018-10-21 11:46 	(:0)
+~~~