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Beginners Guide for Who Command in Linux

   Linux TLDR
   Last Updated: December 19, 2025
   No Comments
   Reading time: 3 minutes

   The who command is a built-in Linux utility that shows a list of users
   who are currently logged on to the Linux system.

   In this article, you will learn how to use this command and what
   options it has to offer (with practical examples).

   Table of Contents
   Toggle

     * Tutorial Details
     * Usage of the Who Command
     * Who Command Options
          + Display the Output with Header
          + Display the Output in Verbose Mode
          + Display the Time of the Last System Boot
          + Display the Users Idle Time
          + Display the Dead Processes
          + Display the Active Processes Spawned by Init
          + Display the Total Number of Logged-In Users with their Name
          + Display the Users Terminal Status
          + Display the Users Login Processes
          + Display the Current Runlevel
          + Display the User-Associated Information with the Current
            Terminal
     * Historical Data of the Users

Tutorial Details

   Description             Who
   Difficulty Level        Low
   Root or Sudo Privileges No
   OS Compatibility        Ubuntu, Manjaro, Fedora, etc.
   Prerequisites           who
   Internet Required       No

Usage of the Who Command

   The who command takes two arguments: one is the option, and the other
   is the file.
$ who [OPTION] [FILE]

   If the file field is left empty, then the who command will pull the
   user related information from the “/var/run/utmp” file.

   The following is the output when this command is executed without any
   options:
$ who

   Output:
   who command output

   The above output contains four fields, followed by
     * The name of the logged-in user.
     * The user’s terminal.
     * The time when the user logged in.
     * Host name or IP address from where the user logged-in.

   So far, we’ve seen what the output is when no options are specified;
   now let’s see what the options have to offer.

Who Command Options

   The who command provides various options that can change the output
   based on the specified options, so let’s start with the

Display the Output with Header

   The “-H” flag will display the header for each column in the output.
$ who -H

   Output:
   who command with header output

Display the Output in Verbose Mode

   The “-a” flag will display the output with additional information that
   includes the info provided by the “-b“, “-d“, “-l“, “-p“, “-r“, “-t“,
   “-T“, and “-u” options.
$ who -a

   Output:
   who command output in verbose mode

   This way, you can get all the information instead of specifying each
   option separately.

Display the Time of the Last System Boot

   The “-b” flag will show the time of the last system boot in standard
   format.
$ who -b

   Output:
   who command output with last system boot time

Display the Users Idle Time

   The “-u” flag will show the user’s idle time, which is basically the
   last time the user interacted with the terminal.
$ who -u

   Output:
   who command output with users idle time

   As you can see from the above picture, the “linuxtldr” user has been
   idle for 6 minutes and 16 seconds.

Display the Dead Processes

   The “-d” flag will list all the dead processes under the referenced
   username.
$ who -d

   Output:
   who command output with dead processes

Display the Active Processes Spawned by Init

   The “-p” flag will show a list of all the processes spawned by the
   init.
$ who -p

   Output:
   who command output with processes spawned by init

Display the Total Number of Logged-In Users with their Name

   The “-q” flag will show the name of all the logged-in users to the
   system, including their count.
$ who -q

   Output:
   Display the all the logged-in users

Display the Users Terminal Status

   The “-T” flag will show you the terminal status next to each username;
   it defines whether the user’s terminal has permission for writing
   messages or not.
     * How to Check, Allow, or Disallow Terminal Write Access in Linux

$ who -T

   Output:
   who command output with user terminal status

   The following is the list of all the possible permissions:
     * “+” – The terminal is writable.
     * “-” – The terminal is not writable.
     * “?” – Bad line encountered.

Display the Users Login Processes

   The “-l” flag will show the user login processes, or it can be stated
   as a list of the available terminals.
$ who -l

   Output:
   who command output with login processes

Display the Current Runlevel

   The “-r” flag can be used to check the current runlevel of the system.
$ who -r

   Output:
   Print the current runlevel of the system

Display the User-Associated Information with the Current Terminal

   The “-m” flag will only show user related information that is
   associated with the current terminal (or stdin).
$ who -m

   Output:
   show the user information associated with the active terminal

Historical Data of the Users

   As I’ve stated earlier, this command utilizes the “utmp” file to give
   the user information, but another file with the name “wtmp” keeps the
   historical data of the “utmp” file.

   You can read this file using the who command to get information about
   the past logins.
$ who /var/log/wtmp

   Output:
   Historical data for logged-in users

   Identical to this, the “btmp” file keeps the record of failed logins.
$ who /var/log/btmp

   Output:
   Historical data of failed login

   So, here comes the end of this article.

   If you have any questions or queries related to this topic, then feel
   free to ask them in the comment section.

   Till then, peace!
   SHARE:

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