Dockerfile：在一行中设置多个环境变量

问题描述

我的印象是，可以如下将环境变量设置在一行上，以最大程度地减少中间图像。

 从阿尔卑斯山出发：3.6 
 ENV RUBY_MAJOR 2.4 \ 
 RUBY_VERSION 2.4.1 \ 
 RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 \ 
RUSION_MS VER2.6 
  

但是，根据此代码段运行容器并调用＃set | grep RU 我看到这些变量没有单独分配，而是组合为一个字符串。

  RUBY_MAJOR ='2.4 RUBY_VERSION 2.4.1 RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 RUBYGEMS_VERSION 2.6.12 BUNDLER_VERSION 1.15.3'
  但是，如果我按如下所示明确设置每个变量，则可以得到预期的输出，并且在调用变量。 
  ENV RUBY_MAJOR 2.4 
 ENV RUBY_VERSION 2.4.1 
 ENV RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614CC50822dDC1FE .12 
 ENV BUNDLER_VERSION 1.15.3 
  
 问题：是否可以在一行上组合环境变量的设置？如果是这样，我该怎么办？ 
解决方案
有两种用于指定环境的格式。如果需要单个变量，则可以使用以下格式
  ENV XY 
  
这会将X分配为 Y  
  ENX XYZ 
  
这会将X分配为 YZ  
 
 
 
如果需要分配多个环境变量，则可以使用其他格式
  ENV X = YZ = A 
  
这会将X指定为 Y 和Z为 A 。因此，您的 Dockerfile 应该是
  FROM高山：3.6 
 ENV RUBY_MAJOR = 2.4 \ 
 RUBY_VERSION = 2.4.1 \ 
 RUBY_DOWNLOAD_SHA256 = 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 \ 
 RUBYGEMS_VERSION = 2.612。 
 RUN env 
  
 
I was under the impression that environmental variables could be set on a single line as follows so as to minimize intermediary images.
FROM alpine:3.6
ENV RUBY_MAJOR 2.4 \
    RUBY_VERSION 2.4.1 \
    RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 \
    RUBYGEMS_VERSION 2.6.12 \
    BUNDLER_VERSION 1.15.3
However, running a container based off of this snippet and calling # set |grep RU I see that the variables are not being assigned separately, but are combined into a single string.
RUBY_MAJOR='2.4     RUBY_VERSION 2.4.1     RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654     RUBYGEMS_VERSION 2.6.12     BUNDLER_VERSION 1.15.3'
However, if I explicitly set each variable as below, I get the expected output and there are no errors when calling the variables. 
ENV RUBY_MAJOR 2.4
ENV RUBY_VERSION 2.4.1
ENV RUBY_DOWNLOAD_SHA256 4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654
ENV RUBYGEMS_VERSION 2.6.12
ENV BUNDLER_VERSION 1.15.3
Question: Is  it is possible to combine the setting of environment variables on a single line? If so, how would I do it? And is it a good practice?
 解决方案 
There are two formats for specifying environments. If you need single variable then you below format
ENV X Y
This will assign X as Y
ENX X Y Z
This will assign X as Y Z
If you need to assign multiple environment variables then you use the other format
ENV X=Y Z=A
This will assign X as Y and Z as A. So your Dockerfile should be
FROM alpine:3.6
ENV RUBY_MAJOR=2.4 \
    RUBY_VERSION=2.4.1 \
    RUBY_DOWNLOAD_SHA256=4fc8a9992de3e90191de369270ea4b6c1b171b7941743614cc50822ddc1fe654 \
    RUBYGEMS_VERSION=2.6.12 \
    BUNDLER_VERSION=1.15.3

RUN env
                        
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