Linux

Replace the last pipe with a semicolon, and check the chars at the end of the line.

Sorry, but the idea of using "ps" inside (any form of) a script to manipulate processes is flawed from the start.

Processes are allowed to lie about their credentials, except to their parents. For automatically (a script is a sort of automaton) parsing ps output scripts are simply not smart enough. ps is designed for interactive use because systems administrators are supposed to be smarter than scripts.

Having said this: i do not know this hawkagent program, but it has to be started somewhere. This "somewhere" is most probably /etc/inittab. Start it there with the clause respawn and the system will restart it for you every time it stops. The system (to be precise: its init process) will even be safe in doing so because init will be the trueparent of the process.

Everything else is risky at best and terminal to the system at worst.

I hope this helps.

bakunin

PS: if your system has no /etc/inittab get runit or daemontools.

is there a way to come out automatically from nohup? Following code remains in a hung state and control is never returned.

Code:

nohup ./hawkagent_BWQA &

"Control" is not meant to return. By sending the process to background with & you chop it off normal terminal stdin. And, with nohup on top, you remove the HUP signal path from its parent (your interactive process), and the init process becomes its parent.
You'll have to build in extra code for interaction with the outer world, e.g. via FIFOs.

I think in some|most cases neither the & nor the nohup chop the shell's input and output.
Therefore I recommend to explicitly redirect the std handles

Code:

nohup ./hawkagent_BWQA </dev/null >/dev/null 2>&1 &

The phrasing may have been a bit unlucky. If a process sent to background tries to read from the terminal, although still having stdin pointing to the terminal, it assumes a stopped state, so it doesn't interfere with the interactive shell. By sending a process to bg, you intentionally cede interactive control.
You can get back "control" by putting it into foreground with the fg command.