I have background application A.
I want to create application B to configure application A on the fly.
So, how can I detect if A is running and send some messages to A?
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If you just want to change the program's configuration, the typical method of doing that is to update its conf file, then send it a SIGHUP signal, which it is programmed to respond to by reloading its conf file ( see
If you need more complex communication with the program, you will want to use either a fifo or unix domain socket. A fifo ( see
Background application are called "daemon" in Unix & Linux world.
They are standardized in many ways, one way is how to get their pid. They usually create a pid file in
With their pid, you can know nearly everything about them with the help of /proc. You can know if it's still active, memory used, memory mapping, files open, etc, etc.
And as sr_ said, you can then use IPC methods in order to communicate with it.