Linux who command
On Unix-like operating systems, the who command displays users logged in to the system.
This page covers the GNU/Linux version of who.
Description
The who command prints information about all users who are currently logged in.
Syntax
who [ OPTION ]... [ FILE ] [ am i ]
Options
| -a, --all | Same as using the options -b -d --login -p -r -t -T -u. |
| -b, --boot | Display the time of the last system boot. |
| -d, --dead | Display dead processes. |
| -H, --heading | Print a line of column headings. |
| --ips | Print IP addresses instead of hostnames. With --lookup, canonicalizes based on stored IP, if available, rather than stored hostname. |
| -l, --login | Print system login processes. |
| --lookup | Attempt to canonicalize hostnames via DNS. |
| -m | Only print information about the user and host associated with standard input (the terminal where the command was issued). This method adheres to the POSIX standard. |
| -p, --process | Print active processes spawned by init. |
| -q, --count | Displays all login names, and a count of all logged-on users. |
| -r, --runlevel | Print the current runlevel. |
| -s, --short | Print only name, line, and time fields, which is the default. |
| -t, --time | Print the last time the system clock was changed, if the information is available. |
| -T, -w, --mesg | Add a character which indicates the state of the terminal line: "+" if the terminal is writable, "-" if it's not, or "?" if a bad line is encountered. |
| -u, --users | Print the idle time for each user, and the process ID. |
| --message | Same as -T. |
| --writable | Same as -T. |
| --help | Display a help message, and exit. |
| --version | Display version information, and exit. |
Notes
If FILE is specified, who gathers its information from this file. Otherwise, it reads from a default file location (usually /var/run/utmp).
If the arguments "am i" are specified, who assumes the -m option.
Examples
who
Displays the username, line, and time of all currently logged-in sessions. For example:
who am i
Displays the same information, but only for the terminal session where the command was issued, for example:
alan pts/3 2013-12-25 08:52 (:0.0)
who -aH
Displays "all" information, and headers above each column of data, for example:
NAME LINE TIME IDLE PID COMMENT EXIT
2014-01-17 07:00 154 id=si term=0 exit=0
system boot 2014-01-17 07:00
run-level 2 2014-01-17 07:00 last=S
2014-01-17 07:01 1607 id=l2 term=0 exit=0
LOGIN tty6 2014-01-17 07:01 2809 id=6
LOGIN tty5 2014-01-17 07:01 2808 id=5
LOGIN tty4 2014-01-17 07:01 2807 id=4
LOGIN tty2 2014-01-17 07:01 2805 id=2
LOGIN tty1 2014-01-17 07:01 2804 id=1
LOGIN tty3 2014-01-17 07:01 2806 id=3
pts/0 2014-01-17 11:31 2811 id=ts/0 term=0 exit=0
lucy + pts/1 2014-01-17 22:42 . 6609 (:0.0)
pts/2 2014-01-18 02:14 0 id=/2 term=0 exit=0
pts/3 2014-01-18 02:08 0 id=/3 term=0 exit=0
pts/4 2014-01-17 21:30 0 id=/4 term=0 exit=0
lucy + pts/0 2014-01-17 22:01 01:04 6330 (:0.0)
Related commands
date — Output the current date and time.
last — Display a listing of the most recently logged-in users.
login — Begin a session on a system.
mesg — Control if (non-root) users can send messages to your terminal.
su — Become the superuser or another user.
w — Show who is logged on and what they are doing.
whoami — Print your effective userid.