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Full Discussion: Log Out SSH User in Bash
Top Forums Shell Programming and Scripting Log Out SSH User in Bash Post 302814793 by FreddoT on Thursday 30th of May 2013 08:19:58 AM
Old 05-30-2013
Wrench Log Out SSH User in Bash

So, I've been writing a system to allow users temporary access onto a system.

Essentially, there's a web server with a PHP script, the PHP script takes a Username & Password from a webform, and passes it to a script, createusr.sh.

The script looks something like this:

Code:
pass=$(perl -e 'print crypt($ARGV[0], "password")' $2)
sudo /usr/sbin/useradd $1 -s /bin/bash -p $pass -d /home/onlineusers/$1 -m
sudo /bin/chmod 700 /home/onlineusers/$1
sleep 1800
sudo /usr/sbin/userdel -f $1
sudo /bin/rm -rf /home/onlineusers/$1

Basically it creates a user, using the passed parameters, and force creates their home directory. It then makes that directory only accessible to said user, before sleeping for half an hour.

After that time it deletes the user and their home directory. But I have one problem. If the user is still logged on at that point, then the user deletion has no effect, as the user can still work.

At the moment, I am thinking of using:

Code:
pgrep -t <user's tty>

and then killing the bash, but I'm not sure how I can get the TTY of a user logged in through SSH?

Maybe somehow "grep" with "w" might do it, but not if the username contains something like "load" which is featured elsewhere in the output from "w".

Besides this, is there any way that I can send a message to a logged in user, saying something like "5 minutes left"?

Code:
write

seems like a possibility, but I'm not sure exactly how this would be implemented.

Last edited by FreddoT; 05-30-2013 at 09:27 AM..
 

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FLUSH(3)								 1								  FLUSH(3)

flush - Flush system output buffer

SYNOPSIS
void flush (void ) DESCRIPTION
Flushes the system write buffers of PHP and whatever backend PHP is using (CGI, a web server, etc). This attempts to push current output all the way to the browser with a few caveats. flush(3) may not be able to override the buffering scheme of your web server and it has no effect on any client-side buffering in the browser. It also doesn't affect PHP's userspace output buffering mechanism. This means you will have to call both ob_flush(3) and flush(3) to flush the ob output buffers if you are using those. Several servers, especially on Win32, will still buffer the output from your script until it terminates before transmitting the results to the browser. Server modules for Apache like mod_gzip may do buffering of their own that will cause flush(3) to not result in data being sent immedi- ately to the client. Even the browser may buffer its input before displaying it. Netscape, for example, buffers text until it receives an end-of-line or the beginning of a tag, and it won't render tables until the </table> tag of the outermost table is seen. Some versions of Microsoft Internet Explorer will only start to display the page after they have received 256 bytes of output, so you may need to send extra whitespace before flushing to get those browsers to display the page. RETURN VALUES
No value is returned. SEE ALSO
ob_flush(3), ob_clean(3), ob_end_flush(3), ob_end_clean(3). PHP Documentation Group FLUSH(3)
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