Linux / Unix who Command Examples To List Users on The Systems

I am a new Linux and Unix system user. How do I display who is logged on my Linux or Unix-like operating system using shell prompt?

You need to use who command to display users who are currently logged in your server.

This command is useful to find out the following information:

1. Time of last system boot.
2. Current run level.
3. List of logged in users and more.

Purpose

Display who is on the system.

Syntax

The basic syntax is as follows:

who
who am i
who [options] [File]
who --help
who --version
who | grep 'userNameHere'

Where,

• If no non-options provided, who displays the following information for each user currently logged on:
• login name
• terminal line
• login time
• remote hostname or X display
• If you give one non-option argument, who uses that instead of a default system-maintained file such s /var/run/utmp as the name of the file containing the record of users logged on.
• If given two non-option arguments, who prints only the entry for the user running it preceded by the hostname. Traditionally, the two arguments given are ‘am i’, as in ‘who am i’.

who command examples

To show a list of all the users currently logged in to the system, type:
$ who
Sample outputs:

Fig. 01: Identifying who is logged on your server

Show or list users logged in

Type the command:
$ who -u

Show time of last system boot

To display time of last system boot pass the -b option to who command:
$ who -b
Sample outputs:

         system boot  2014-01-05 10:02

The output in this example, shows that the system was booted since 10:02 on 05 January.

Show dead processes on the system

You need pass the -d option to who command:
$ who -d
OR
$ who -d -H
Sample outputs:

NAME     LINE         TIME             IDLE          PID COMMENT  EXIT
         pts/1        2014-01-11 09:17             56094 id=ts/1  term=0 exit=0
         pts/2        2014-01-05 15:46             11070 id=ts/2  term=0 exit=0
         pts/2        2014-01-08 03:31              3614 id=/2    term=0 exit=0
         pts/1        2014-01-11 16:54             64559 id=/1    term=0 exit=0
         pts/3        2014-01-11 17:13             15818 id=/3    term=0 exit=0
         pts/4        2014-01-25 11:02             46807 id=ts/4  term=0 exit=0

Show system login processes

To just display system login processes pass the -l option:
$ who -l
OR
$ who -l -H
Sample outputs:

NAME     LINE         TIME             IDLE          PID COMMENT
LOGIN    tty2         2014-01-05 10:03              8750 id=2
LOGIN    tty1         2014-01-05 10:03              8748 id=1
LOGIN    tty3         2014-01-05 10:03              8752 id=3
LOGIN    /dev/ttyS1   2014-01-05 10:03              8747 id=v/tt
LOGIN    tty4         2014-01-05 10:03              8754 id=4
LOGIN    tty5         2014-01-05 10:03              8756 id=5
LOGIN    tty6         2014-01-05 10:03              8758 id=6

Count all login names and number of users logged on the system

To count all login names and number of users logged on:
$ who -q
Sample outputs:

Fig.02: Displaying and counting all users logged on

Display the current runlevel

To display the current system runlevel, type:
$ who -r
Sample outputs:

         run-level 3  2014-01-05 10:02

You can combine -r and -b options as follows:
$ who -r -b
Sample outputs:

         system boot  2014-01-05 10:02
         run-level 3  2014-01-05 10:02

Display all

The -a is same as same as -bdprtTu options as discussed earlier:
Sample outputs:

NAME       LINE         TIME             IDLE          PID COMMENT  EXIT
           system boot  2014-01-05 10:02
           run-level 3  2014-01-05 10:02
LOGIN      tty2         2014-01-05 10:03              8750 id=2
LOGIN      tty1         2014-01-05 10:03              8748 id=1
LOGIN      tty3         2014-01-05 10:03              8752 id=3
LOGIN      /dev/ttyS1   2014-01-05 10:03              8747 id=v/tt
LOGIN      tty4         2014-01-05 10:03              8754 id=4
LOGIN      tty5         2014-01-05 10:03              8756 id=5
LOGIN      tty6         2014-01-05 10:03              8758 id=6
root     + pts/0        2014-01-27 03:37   .         11149 (10.1.6.120)
           pts/1        2014-01-11 09:17             56094 id=ts/1  term=0 exit=0
           pts/2        2014-01-05 15:46             11070 id=ts/2  term=0 exit=0
           pts/2        2014-01-08 03:31              3614 id=/2    term=0 exit=0
           pts/1        2014-01-11 16:54             64559 id=/1    term=0 exit=0
           pts/3        2014-01-11 17:13             15818 id=/3    term=0 exit=0
           pts/4        2014-01-25 11:02             46807 id=ts/4  term=0 exit=0

who command options

Related media

This tutorial is also available in a quick video format:

Summing up

You learned about who command that show information about users who are currently logged in your Linux or Unix machine. Please read the following manual pages using the man command or help command:

man who
who --help

See also

• /var/run/utmp file.
• /var/log/wtmp file.

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Vivek Gite is an expert IT Consultant with over 25 years of experience, specializing in Linux and open source solutions. He writes about Linux, macOS, Unix, IT, programming, infosec, and open source. Follow his work via RSS feed or email newsletter.