Daemonize

A library for daemonizing an application.

Why

I was interested in how an application can become a daemon, and what it would take to implement a reusable framework for it.

What

Daemonize is a framework consisting of two classes, Application and Daemon, that provides a way to run an application both as a daemon and a non-daemonized application.

How

Using this framework is really easy:

1. Create a class inheriting from the daemonize::Application. This class becomes your 'main class'.
2. Override the Main() method. This becomes the entry point to your program where you start your program flow.
3. In your int main( int argc, char* argv[] ) function, do:
   1. Instantiate an instance of the 'main class', providing the initial desired working directory to be used when run as a daemon.
   2. Call app.RunAsDaemon() to run as daemon, or app.Run() to run as a regular application.
   3. Return the value returned by the Run*() method.

Code flow when running as a daemon

When calling RunAsDaemon(), your application will actually be cloned twice due to how fork() works and how a daemon is started. As such, you need to handle the fact that your application will behave as if it returns three times from the RunAsDaemon() method, once for the original instance, secondly for an intermediate instance and thirdly from the actual daemon process. So if you do things in your int main( int argc, char* argv[] ) after calling RunAsDaemon() that code will be run a total of three times. As such, it is recommended to do no additional work and only return whatever RunAsDaemon() returns.

Signals

The Application class intercepts the signals specified in the myInterceptedSignals member. Among these are SIGINT and SIGTERM. You must override virtual void SignalReceived( int signal ) method and handle the signal yourself according to your needs.