This is a really simple Java library for starting, stopping, and controlling daemon processes written in Java on Unix/Linux. To allow your program to run as a daemon, just link this library into your program. The library does not use native code, nor does it require external shell scripts. All OS-dependent functionality is implemented by executing subprocesses, specifically sh, ps, and mkfifo.

See the ExampleDaemon and ExampleDaemonController classes as an example of how to define a daemon. The ExampleDaemon class has methods for starting the daemon, shutting down the daemon, and receiving commands. The ExampleDaemonController is an example of an entry point class: for example, if you are doing a single-jar deployment, it would be the main class.

Running the example daemon: first compile the classes (will happen automatically if you import the project into Eclipse). Then cd to the root directory of the project. Run the following commands:

./mkdemojar.sh
java -jar demo.jar start
java -jar demo.jar hello
java -jar demo.jar shutdown

The example shows how you might package your daemon in a single jar file for deployment. The last three commands will (respectively) start the daemon, send a command ("hello") to the daemon, and shut down the daemon. A file called log.txt will be created to capture the standard output and standard error of the daemon. Each command (start/hello/shutdown) will be logged in this file.

Some things to note:

• The pid file and the FIFO used to control the running daemon will be created in the current directory (the directory the entry point main method is started from).
• Each running daemon process will have an "instance name". A default instance name is used if none is provided when the daemon is started. You can run many daemon processes from the same codebase in the same directory as long as they all have different instance names.

To build the code as a jar file, build the jar target in the provided build.xml using Ant. This will create a jar file called daemon.jar.

The code is distributed under the MIT license.

Let me know if you have any feedback, patches, etc.

David Hovemeyer david.hovemeyer@gmail.com