Find the IP address of the client in an SSH session

Question

I have a script that is to be run by a person that logs in to the server with SSH.

Is there a way to find out automatically what IP address the user is connecting from?

Of course, I could ask the user (it is a tool for programmers, so no problem with that), but it would be cooler if I just found out.

Ute

propose moving to serverfault, still great question though – Rheumy

Answer 1

Check if there is an environment variable called:

$SSH_CLIENT

OR

$SSH_CONNECTION

(or any other environment variables) which gets set when the user logs in. Then process it using the user login script.

Extract the IP:

$ echo $SSH_CLIENT | awk '{ print $1}'
1.2.3.4
$ echo $SSH_CONNECTION | awk '{print $1}'
1.2.3.4

Transient

@cwd i want to replace the ip in this command "iptables -A INPUT -s 93.203.118.251 -p tcp --destination-port 443 -j DROP" is that possible? – Kalli

This was REMOTEHOST for me. – Grippe

only works with non-sudoed users. e.g. if you have an ssh user and then escalate to root, a new shell is created and these variables are lost, unless you can trace back through the tree to find the original ssh pid and get the variables from /proc/$PID/environ – Diacritic

thanks to https://mcmap.net/q/14333/-extract-substring-in-bash this answer can be improved to simply ${SSH_CLIENT%% *} – Verdha

@Diacritic look into sudo -E – Verdha

Had to use echo $SSH_CONNECTION | awk '{print $3}' – Shipshape

This is my go to for finding all env vars with a certain substring env | grep SSH | sort – Dolorous

Sometimes, it won't work if there was a network reconnection and IP address changed, but an actual SSH session stayed alive, for example. It may return a previous(old) IP address. Consider trying using who instead. – Tirza

Answer 2

You could use the command:

server:~# pinky

that will give to you somehting like this:

Login      Name                 TTY    Idle   When                 Where 

root       root                 pts/0         2009-06-15 13:41     192.168.1.133

Tutelary

That's awesome :-) Nerd humour ftw once again. According to pinky --help: A lightweight 'finger' program; print user information. The utmp file will be /var/run/utmp. – Manualmanubrium

Why is it the my 'Where' in my output only shows the machine name and not the ip address? – Yunyunfei

Probably you got the nameserver configurated in your machine. – Tutelary

pinky will show all logged in users, not just yourself – Diacritic

Answer 3

Try the following to get just the IP address:

who am i|awk '{ print $5}'

Exacerbate

pretty sure if you write whoami and you will get the name of the logged in user. there's no fifth thing or ip to print sorry. but whoami is a useful command – Lawford

who am i != whoami on my Linux at least. There is a fifth thing, and it is the host name of the client. – Wallen

For anyone else wondering about who am i: The manpage for who says: If ARG1 ARG2 given, -m presumed: 'am i' or 'mom likes' are usual.. So really anything with two words works, also things like who likes icecream. – Paradigm

Building on this answer, I reduced it to who -m --ips|awk '{print $5}' so that I had only IP and no reverse-dns answer. Thanks for the help on who am i! – Rumpus

Some output may look like admin pts/0 Sep 30 13:20 1.1.1.1, so this better be date-format-independent – Ritualism

Fails with tmux: who am i|awk '{ print $5}' (tmux(2445).%3) – Metalwork

Answer 4

Just type the following command on your Linux machine:

who

Relative

Answer 5

who | cut -d"(" -f2 |cut -d")" -f1

Swetiana

Answer 6

Improving on a prior answer. Gives ip address instead of hostname. --ips not available on OS X.

who am i --ips|awk '{print $5}' #ubuntu 14

more universal, change $5 to $6 for OS X 10.11:

WORKSTATION=`who -m|awk '{print $5}'|sed 's/[()]//g'`
WORKSTATION_IP=`dig +short $WORKSTATION`
if [[ -z "$WORKSTATION_IP" ]]; then WORKSTATION_IP="$WORKSTATION"; fi
echo $WORKSTATION_IP

Gomar

Answer 7

A simple command to get a list of recent users logged in to the machine is last. This is ordered most recent first, so last | head -n 1 will show the last login. This may not be the currently logged in user though.

Sample output:

root     pts/0        192.168.243.99   Mon Jun  7 15:07   still logged in   
admin    pts/0        192.168.243.17   Mon Jun  7 15:06 - 15:07  (00:00)    
root     pts/0        192.168.243.99   Mon Jun  7 15:02 - 15:06  (00:03)    
root     pts/0        192.168.243.99   Mon Jun  7 15:01 - 15:02  (00:00)    
root     pts/0        192.168.243.99   Mon Jun  7 13:45 - 14:12  (00:27)    
root     pts/0        192.168.243.99   Mon May 31 11:20 - 12:35  (01:15)    
...

Washrag

Answer 8

who am i | awk '{print $5}' | sed 's/[()]//g' | cut -f1 -d "." | sed 's/-/./g'


export DISPLAY=`who am i | awk '{print $5}' | sed 's/[()]//g' | cut -f1 -d "." | sed 's/-/./g'`:0.0

I use this to determine my DISPLAY variable for the session when logging in via ssh and need to display remote X.

Arela

Useful one liner to add my IP to .htaccess files. Thank you. I've made a modification for FreeBSD: who am i | awk '{print $6}' | sed 's/[()]//g' | sed 's/\./\\./g' The last part escapes the dots. – Nonego

Answer 9

netstat -tapen | grep ssh | awk '{ print $4}'

Parody

doesn't work on CentOS 6.9 (net-tools 1.60 netstat 1.42) (No info could be read for "-p": geteuid()=507 but you should be root.) – Verdha

@Verdha does sudo ss -tapen | grep ssh | awk '{ print $4}'|grep -v ':22$' work? – Metalwork

That doesn't quite work for me, had to use netstat -tapen | grep -F :22 | grep ESTABLISHED – Faithfaithful

Answer 10

You can get it in a programmatic way via an SSH library (https://code.google.com/p/sshxcute)

public static String getIpAddress() throws TaskExecFailException{
    ConnBean cb = new ConnBean(host, username, password);
    SSHExec ssh = SSHExec.getInstance(cb);
    ssh.connect();
    CustomTask sampleTask = new ExecCommand("echo \"${SSH_CLIENT%% *}\"");
    String Result = ssh.exec(sampleTask).sysout;
    ssh.disconnect();   
    return Result;
}

Wane

Answer 11

an older thread with a lot of answers, but none are quite what i was looking for, so i'm contributing mine:

sshpid=$$
sshloop=0
while [ "$sshloop" = "0" ]; do
        if [ "$(strings /proc/${sshpid}/environ | grep ^SSH_CLIENT)" ];
then
                read sshClientIP sshClientSport sshClientDport <<< $(strings /proc/${sshpid}/environ | grep ^SSH_CLIENT | cut -d= -f2)
                sshloop=1
        else
                sshpid=$(cat /proc/${sshpid}/status | grep PPid | awk '{print $2}')
                [ "$sshpid" = "0" ] && sshClientIP="localhost" && sshloop=1
        fi
done

this method is compatible with direct ssh, sudoed users, and screen sessions. it will trail up through the process tree until it finds a pid with the SSH_CLIENT variable, then record its IP as $sshClientIP. if it gets too far up the tree, it will record the IP as 'localhost' and leave the loop.

Diacritic

Answer 12

I'm getting the following output from who -m --ips on Debian 10:

root pts/0 Dec 4 06:45 123.123.123.123

Looks like a new column was added, so {print $5} or "take 5th column" attempts don't work anymore.

Try this:

who -m --ips | egrep -o '([0-9]{1,3}\.){3}[0-9]{1,3}'

Source:

• @Yvan's comment on @AlexP's answer
• @Sankalp's answer

Outstay

Answer 13

netstat -tapen | grep ssh | awk '{ print $10}'

Output:

two # in my experiment

netstat -tapen | grep ssh | awk '{ print $4}' 

gives the IP address.

Output:

127.0.0.1:22 # in my experiment

But the results are mixed with other users and stuff. It needs more work.

Lawford

my netstat only gives a truncated address for IPv6 and "127.0.0.1:22" is the server rather than the client, (which was specified in the question.) – Metalwork

Answer 14

Assuming he opens an interactive session (that is, allocates a pseudo terminal) and you have access to stdin, you can call an ioctl on that device to get the device number (/dev/pts/4711) and try to find that one in /var/run/utmp (where there will also be the username and the IP address the connection originated from).

Luanneluanni

Answer 15

There could be a race condition, but this solution works as an ssh command. All the other solutions shown here require an ssh login.

$ ssh {host} last -1 | head -1 | awk '{print $3}'

Notochord

Answer 16

Usually there is a log entry in /var/log/messages (or similar, depending on your OS) which you could grep with the username.

Buzzer

Answer 17

netstat will work (at the top something like this) tcp 0 0 10.x.xx.xx:ssh someipaddress.or.domainame:9379 ESTABLISHED

Pickett

Thank you SO much for this answer, I ended up doing 'netstat | grep ssh'. – Thou

For security reasons this is bad because anybody could be connected to that port, not just you. – Hypoderma

Answer 18

Linux: who am i | awk '{print $5}' | sed 's/[()]//g'

AIX: who am i | awk '{print $6}' | sed 's/[()]//g'

Soredium

Answer 19

Search for SSH connections for "myusername" account;

Take first result string;

Take 5th column;

Split by ":" and return 1st part (port number don't needed, we want just IP):

netstat -tapen | grep "sshd: myusername" | head -n1 | awk '{split($5, a, ":"); print a[1]}'

---

Another way:

who am i | awk '{l = length($5) - 2; print substr($5, 2, l)}'

Supervise

sudo ss -tapen | grep "sshd: $(whoami)"|head -n1|awk '{split($5, a, ":"); print a[1]}' says my ssh client is from 2a02 and your "Another way:" says tmux(2445).%3 – Metalwork

Answer 20

One thumb up for @Nikhil Katre's answer :

Simplest command to get the last 10 users logged in to the machine is last|head.

To get all the users simply use last command

The one using who or pinky did what is basically asked. But But But they don't give historical sessions info.

Which might also be interesting if you want to know someone who has just logged in and logged out already when you start this checking.

if it is a multiuser system. I recommand add the user account you are looking for:

last | grep $USER | head

EDIT:

In my case, both $SSH_CLIENT and $SSH_CONNECTION do not exist.

Ansermet