loginlimit

loginlimit is a program that is put into a users .profile. It will prevent a user from logging in if:

The user would exceed the default session limit
The user would exceed their personal session limit
Logins are disabled for everyone
Logins are disabled for that particular user (handy if they are behind on their monthly payments to IT for the privilege of logging in ;)

The deflected user gets a message, displayed in plain text if using a regular terminal, or in a pop-up box if using User Interface™

The line in .profile that accomplishes this is:

/usr/local/bin/loginlimit $( who am i | cut -f1 ) || exit
This assumes that the loginlimit script is put into /usr/local/bin

Setup

First, download the tarball from here
Use the command 'tar -xvf loginlimits.tar' to untar it, you will create a directory called loginlimits.

cd to loginlimits:

Edit loginOverLimit.msg - this is what will be displayed if a user is trying to log in over their session limit. The word "loginLimit" will be replaced by their personal limit in the message that gets displayed.
Edit loginDisabled.msg - this is what will be displayed if logins are currently disabled for a user or all users.
Copy these two files to /usr/local/etc, and
'chmod 444 /usr/local/etc/loginOverLimit.msg /usr/local/etc/loginDisabled.msg'
so that both files are readable by all users.
Note: You may have to create /usr/local/etc first...
Copy loginlimit to /usr/local/bin, and
'chmod 755 /usr/local/bin/loginlimit'

Usage

To make a user "limitable" - insert the following line in their .profile (ksh, sh, or pk-ksh, pk-sh) near the end (exactly where depends on your .profile...)
/usr/local/bin/loginlimit $( who am i | cut -f1 ) || exit

To disable logins for all loginlimit users, touch /usr/local/etc/loginlimit.4all. To re-enable, rm /usr/local/etc/loginlimit.4all.
To disable logins for an individual user or a group of users, put their names in /usr/local/etc/loginlimit.list with vi or another editor, one on a line.
To enforce session limits, put a users name followed by a colon and the session limit in the file /usr/local/etc/loginlimit.userLimits - e.g.:
joeuser:3
will limit joeuser to 3 sessions.
/usr/local/etc/loginlimit.userLimits may also contain a line such as
defaultLimit=3
which will set the default session limit to 3 for all users.

There are example files in the loginlimits directory that you untar'd.

You can look at screenshots here.

Requires

bash shell - here's links to get it for:
solaris
HP/UX
AIX