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    <p>Have a look at the <code>killall</code> command. The <code>start</code> within a script often just looks to see if an instance of the program already exists, and if it doesn't it starts it. The stop often just sends a signal to the service using the <code>killall</code> command.</p> <p>Similar things that you may be interested in are editing or replacing the configuration files for a daemon and then sending the daemon the SIGHUP signal telling it that it should reread its configuration.</p> <p>Another related topic is sending a daemon a particular message by calling the daemon's executable with some particular options. This is done this way because the interface that the messages are sent in can change and if it is the same program doing the sending and receiving it is hard to get out of sync. The method of sending messages can vary as well (Unix Domain Sockets, named pipe, editing a configuration file and sending SIGHUP, just about anything you could imagine). One other benefit of this is that the same input verification that the program uses when it runs as a daemon can be used before it sends the message, so if there is an error that the daemon would choke on the instance of the program that you are calling from the command line could go ahead and tell you on the terminal and refuse to pass this on to the daemon.</p> <p>To find the PID of a running service either use a pid file (daemon creates a file in a certain location with its PID in it -- just like old lock files, or do it the same way that <code>killall</code> does -- look through <code>/proc</code> (which is platform specific).</p>
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    1. POCalling "start" to start program and "stop" to close current instance in C
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    1. COThanks nate, I'm leaning towards not even implementing this in the program as it probably doesn't belong in it. As Tom mentioned above, these start | stop options are usually provided by shell scripts and not within the program itself. I just thought it would be easy if another program could just call it with a stop option. Killing is probably never good, so I will try to handle all the closes of fd's, stopping of loops, etc. some other way without relying on the "stop" signal from another program.
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    2. CO@Jack: The reason that I mentioned all of those different ways of sending messages to daemons was that I thought that you might have seen a couple of them in the past and then remembered them as though they were the same. The feel the same. Either way, `killall` can send any signal to a process and most signals can be handled, so the exit doesn't have to be ungraceful.
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