如何在保留新行的同时在Dockerfile中编写多行命令？ [英] How to write commands with multiple lines in Dockerfile while preserving the new lines?

问题描述

我想在Dockerfile中编写以下RUN命令。但是，docker不会保留新行。

  RUN echo [repo] \ 
 name = YUM Repository \ 
 baseurl = https://example.com/packages/ enabled 
 enabled = 1 \ 
 gpgcheck = 0> /etc/yum.repos.d/Repo.repoxyz 
  

我知道每行末尾的\ 会换行。但是，有什么方法可以写多行来保存新行？

解决方案

您可以使用所谓的 ANSI -C用 $'...'引用。 它最初是 ksh93 功能，但现在可以在 bash，zsh，mksh，FreeBSD sh 和 busybox的灰中使用（但只有在使用ENABLE_ASH_BASH_COMPAT编译时才可以。）

为默认情况下，RUN使用 / bin / sh 作为外壳程序，您需要先使用SHELL指令切换到bash之类的方式。 / p>

以 $'开始命令，以'并使用 \n\ 换行，例如：

  SHELL [ / bin / bash， -c] 
 
 RUN echo $'[repo] \n\ 
名称= YUM存储库\n\ 
 baseurl = https://example.com/packages/已启用
 = 1已启用
 gpgcheck = 0'> /etc/yum.repos.d/Repo.repoxyz 
  




I want to write the following RUN command in the Dockerfile. But, docker is not preserving the new lines.

RUN echo "[repo] \
name            = YUM Repository \
baseurl         = https://example.com/packages/ \
enabled         = 1 \
gpgcheck        = 0" > /etc/yum.repos.d/Repo.repoxyz

I know that \ at the end of each line escapes the new line. But, is there any way that I can write multiple lines preserving the new line?

解决方案

You can use what is called "ANSI-C quoting" with $'...'. It was originally a ksh93 feature but it is now available in bash, zsh, mksh, FreeBSD sh and in busybox's ash (but only when it is compiled with ENABLE_ASH_BASH_COMPAT).

As RUN uses /bin/sh as shell by default you are required to switch to something like bash first by using the SHELL instruction.

Start your command with $', end it with ' and use \n\ for newlines, like this:

SHELL ["/bin/bash", "-c"]

RUN echo $'[repo] \n\
name            = YUM Repository \n\
baseurl         = https://example.com/packages/ \n\
enabled         = 1 \n\
gpgcheck        = 0' > /etc/yum.repos.d/Repo.repoxyz

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