What does ${PORT:-3000} mean in Heroku Procfile?

Question

web: bundle exec puma -t 5:5 -p ${PORT:-3000} -e ${RACK_ENV:-development}

At first I thought 3000 was a default value, but in fact foreman uses port 5000 if PORT is missing in development.

Question: What does the notation ${VARIABLE:-3000} mean?

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Update: It seems like puma is the culprit: Foreman/Puma isn't using the specified port in dev env

KARASZI István · Accepted Answer · 2022-09-30T09:46:03.723

3

That is the default value of the VARIABLE.

Use Default Values. If parameter is unset or null, the expansion of word is substituted. Otherwise, the value of parameter is substituted.

In this case if the PORT variable is not set then its value will be 3000 and similarly if RACK_ENV is not set then it will be development.

edited Sep 30 '22 at 09:46

answered Dec 02 '16 at 13:00

KARASZI István

1

Any idea why it uses 5000 instead of 3000? – João Souza Dec 02 '16 at 13:02
Have you checked your `.env` file? – KARASZI István Dec 02 '16 at 13:05
1

Yes, there is no PORT variable – João Souza Dec 02 '16 at 13:07
When I set PORT=3000 it uses 3000, if I don't set anything it uses 5000. I copy-pasted the Procfile, no typos there. – João Souza Dec 02 '16 at 13:09
Well, you can always log the `PORT` environment variable out somewhere. My assumption is that it has been set somewhere. – KARASZI István Dec 02 '16 at 13:11
Never mind, thank you, it seems to be an issue with Puma: http://stackoverflow.com/questions/29595129 – João Souza Dec 02 '16 at 13:12

1 Answers1