Spinner

Spinner starts and then stops when you tell it to.

Getting started

The following procedure illustrates how to build and run the spinner Go app. App spinner exits with a 0 exit code because it handles the SIGTERM Unix signal.

1. Get the code.

   git clone git@github.com:mbigras/spinner.git
   cd spinner
   

2. Build the app.

   go build
   

3. Run spinner.

   ./spinner && echo $?
   

4. In a new terminal, send the SIGTERM Unix signal to spinner.

   pkill spinner
   

5. Notice that spinner cleanly exits.

   Your output should look like the following:

   $ ./spinner && echo $?
   Running as pid: 14897
   Got args: []
   Got signal: terminated
   0
   

Docker example

The following example illustrates how to build and run a spinner Docker container. You can stop the container because spinner handles the SIGTERM Unix signal that Docker sends to your container when you run the docker stop command.

1. Get the code.

   git clone git@github.com:mbigras/spinner.git
   cd spinner
   

2. Build the Docker image.

   docker build -t spinner .
   

3. Run the Docker container.

   docker run -it --rm --name spinner spinner foo bar baz && echo $?
   

   You pass the foo, bar, and baz command-line arguments. Docker passes those arguments to spinner because the ENTRYPOINT Docker directive tells Docker to treat spinner as the main exectuable to run.

   Also, the exec ENTRYPOINT form—ENTRYPOINT ["/app/spinner"]—ensures that /bin/sh shell running inside your Docker container won't block Unix signals.

4. In a new terminal, stop the container.

   docker stop spinner
   

5. Notice that spinner cleanly exits.

   Your output should look like the following:

   $ docker run -it --rm --name spinner spinner foo bar baz && echo $?
   Running as pid: 1
   Got args: [foo bar baz]
   Got signal: terminated
   0