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IP address from a pseudo-terminal device

Last Modified: 2013-12-06
How can i find the IP address or the host name of people telneting to my UNIX machine. This is to be used in a shell script and should be clean. I.e i would prefer not to us finger or last.
I wish to use this in an application that will ftp results back to people who telnet into the UNIX application and who are running a ftpd on their PC's.
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Type in the command "who".

If should give you all of the users logged in.  Users telnet'ed in to your system will have the hostname at the end of their line... usually in parenthesis...

You can parse this in your shell script.


netstat -n|grep :23

will give you a list of all IPs currently attached to your Unix machine via telnet.

"who" gives the username and hostname...

"netstat -n|grep :23" gives the username and IP address


by the way, "who" also gives the pseudo terminal name, "netstat -n|grep :23" doesnt...


On my SCO OpenServer 5.0.5 box a "who" does not show the hostname or IP.  Checked the man, "w -x" is required to get the IP or hostname of the user.  

What flavor of Unix are you running?

My shell scripting is kind of weak but you could put something like this in the .profile or .login of the user ...

#set environment variable
MYTTY=sed<`tty`;export MYTTY

#set IP of user
IPADDR=sed <who -x|grep $MYTTY

#whatever other commands they run

#ftp them their files when done

Both sed commands would need some more work.  In the first one tty returns /dev/tty#, so you'd need to use sed (or awk?) to strip off the leading /dev/.  Then the who -x is going to return a whole line of info, so you'd need to strip out the IP somehow.

Try IPADDR=awk '{print $n}' < `who am i` in their .profile or .login

where n is the field number of the ip address (or hostname, if the address is in /etc/hosts) returned by `who am i`

Depending on your Unix, you may have to add options (e.g. -h) to the `who` command to get it to display the IP address/hostname

Oops - wrong way round; Should have said:

IPADDR=`who am i | awk '{print $n}'`

where n is the field number of the ip address (or hostname, if the address is in /etc/hosts) returned by `who am i`

tfewster, Please re-read the question again. your solution *does not* give the IP address of OTHER people connecting to the system...

Suggest you remove your answer...

mcrider, as I understand it richardgraham's requirement is to get the hostname/address of a particular user session, not just to see who's on the system, possibly with multiple logins. However, I've withdrawn my answer in case I've misunderstood.

richardgraham: In THEIR .profile/.login
IPADDR=`who am i | awk '{print $n}'|sed s/(//|sed s/)//` will return the "address" for that session. Alternatively, you could capture this info. when they run the application to save having to modify everyone's login scripts.

The sed statements i've added deal with the case that "who" returns a hostname (usually in parentheses). The parentheses in the sed statements may need to be "escaped" with \ to prevent them being interpreted by the shell.

If the expected usage is: User logs in, kicks off a query & then logs out, with results being ftp'd to them later, you will have to save their address & tie it to the query results file. Be warned though that automating ftp has it's own problems.

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