How to stop a infinite running process(ztail) started by a ssh session after that session is closed

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http://serverfault.com – I have a peculiar problem. My server supports multiple ssh session simultaneously, so that multiple admins can manage it simultaneously. We have a command which calls ztail to show the compressed log files and when the current ssh session is closed (without pressing ctrlc, to stop the tail command), the command should ideally stop working. But what I observed when I start a new ssh session is that the process ztail is still running in the background and consuming CPU, even though the previous session was closed. How can I determine when the session is closed, so that I can use that variab (HowTos)