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Make CLI use an existing process?

Easiest way to send messages to my linux daemon application? Is it possible that myapp foo barcan cause a callback instead of starting a new process? What is the standard way to communicate with the demon? Is my most sensible choice to stick with PID in /var/runand create a named pipe or socket?

What is the standard way that applications running on the command line communicate with the process of their daemon? I assume it is not possible to request linux to call a callback on input myapp foo bar?

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What is the standard way that applications running on the command line communicate with the process of their daemon?

There are several ways to do this:

Dropboxes & signals

To store the "pid file" is used a lot of places containing the daemon process ID number: /var/run/<app>/<app>.pid, /var/run/<app>.pid(thanks @Adam Katz for editing) /run/<app>/<app>.pid, /run/<app>.pid(see. Askubuntu: why / var / run has been moved to / the run? ).

When the piddaemon process process is known, the command line program (which runs as a separate process) can interact with the daemon in the following ways:

  • Writing something in a prepared place. This can be a regular file, a database table, or any convenient place read by the server.
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