Who starts the prerequisite applications?

Questions / Help
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1

I have two Applications I will call A1 and A2. A1 needs A2 to be already running, so I put A2 in the ‘applications’ list in a1.app.src. But then if I do application:start(a1) I will get the error message {error,{not_started,a2}}. It never gets as far as code I put in a1_app.erl to actually start A2. So who starts a2? Will OTP do it for me or does there have to be a higher level app whose supervisor code starts A2 and then runs A1? Or start them all in order from the ‘erl’ command line?

2

Either you or some other previous application starts A2, or you use application:ensure_all_started/2.

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3

If you build a release a boot script is created which handles starting the dependencies.

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