Introduction to who command examples in Linux

About who

Displays users logged into the system. Executing the who command will tell you which users are currently logged into the system. Executing the who command alone will list the login account, the terminal used, the login time, and where they logged in from or which X display they are using.

describe

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

who syntax

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

Options

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

notes

If a file is specified, who collects its information from that file. Otherwise, it reads from the default file location (usually /var/run/utmp).

If the argument "ami" is specified, who assumes the -m option.

who Example

linuxidc@linuxidc:~$ who

Version View

Displays the username, line, and time of all current login sessions. For example:

who am i

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

linuxmi pts/3 2018-12-02 08:52 (:0.0)

Displays "all" information along with a heading above each column of data, for example:

linuxidc@linuxidc:~$ who -aH

 
Name Line Time Idle Process Number Remarks Exit System Boot 2018-12-02 07:45

Run level 5 2018-12-02 07:46

linuxidc ? :0 2018-12-02 07:47 ? 4569 (:0)

Summarize

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