[英]What does ${PORT:-3000} mean in Heroku Procfile?
Heroku suggests this Procfile command to start Puma on Rails 5 setup : Heroku建议使用此Procfile命令在Rails 5安装程序上启动Puma :
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. 起初,我以为3000是默认值,但实际上,如果开发中缺少
PORT
则领班使用端口5000。
Question: What does the notation ${VARIABLE:-3000}
mean? 问题:符号
${VARIABLE:-3000}
是什么意思?
-- -
Update: It seems like puma is the culprit: Foreman/Puma isn't using the specified port in dev env 更新:看来puma是元凶: 工头/ Puma没有在dev env中使用指定的端口
That is the default value of the VARIABLE
. 这是
VARIABLE
的默认值。
Use Default Values.
使用默认值。 If parameter is unset or null, the expansion of word is substituted.
如果参数未设置或为null,则替换单词的扩展名。 Otherwise, the value of parameter is substituted.
否则,将替换参数的值。
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
. 在这种情况下,如果未设置
PORT
变量,则其值将为3000
;类似地,如果未设置RACK_ENV
则其将被development
。
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