who Command in Linux

In this article, we explain the who command that is bundled in GNU coreutils package.

who is a command-line utility that prints a list of currently logged in users. It can also show the current run level, time of the last system boot, and more.

How to Use the who Command #

The basic syntax for the who command is as follows:

who [OPTION]… [ FILE | ARG1 ARG2 ] 

When invoked without any option or argument, the output looks something like this:

who

root pts/0 2020-11-17 20:10 (10.10.0.2) linuxize pts/1 2020-11-17 20:11 (10.10.0.8) 

who will output a formatted list of all users that are currently logged on the system.

Each line contains four fields separated by one or more spaces:

• The name of the logged user.
• The user's terminal.
• The time when the user logged in.
• The hostname or IP address from where the user is logged in. To force Ips, use the --ips option.

If you want to print the column headings, add the -H (--heading) option:

who -H

NAME LINE TIME COMMENT root pts/0 2020-11-17 20:10 (10.10.0.2) linuxize pts/1 2020-11-17 20:11 (10.10.0.8) 

The command pulls information about the system and who is logged in from the /var/run/utmp file. If you want to use another file, pass the file path to the command.

who accepts two non-option arguments. When invoked with two arguments the command prints information only about the terminal associated with the current user. The same output is displayed when the -m option is used.

You can use any two arguments:

who am iwho mom lovewho foo barwho -m

Each of the commands above will print the same information:

linuxize pts/1 2020-11-17 20:11 (10.10.0.8) 

who Command Options #

who accepts several options that generally are rarely used.

The -b, --boot option tells who to print the time of last system boot:

who -b

 system boot 2020-07-20 19:02 

To get a list of all the dead processes use the -d, --dead option:

who -d

The -r, --runlevel option, tells who to show the current runlevel:

who -r

 run-level 5 2020-07-20 19:02 

To get only the user names and the number of currently logged in users, use the -q, --count option:

who -q

root linuxize # users=2 

The -a, --all option forces who to print all information:

who -a

 system boot 2020-07-20 19:02 LOGIN tty1 2020-07-20 19:02 673 id=tty1 run-level 5 2020-07-20 19:02 root - pts/0 2020-11-17 20:10 . 2212314 (89.205.101.54) pts/2 2020-10-10 10:19 1363538 id=ts/2 term=0 exit=0 linuxize + pts/1 2020-11-17 20:11 01:46 2212387 (89.205.101.54) 

Conclusion #

The who command prints a list of all currently logged in users.

To get additional information about the users who are currently logged in, check the w command.

If you have any questions, please leave a comment below.