echo cat dockerfile 多行文本的创建

#!/bin/bash
echo "test测试" > a.txt #改写文件，不存在则创建。

echo "test测试" >> a.txt #追加文件，在文件末尾添加。

test.sh

#!/bin/bash
cat >a.txt<<EOF # 开始
test测试
多行文本
重定向
到文件
EOF# 结束

dockerfile

FROM ubuntu:18.04

RUN mv /etc/apt/sources.list /etc/apt/sources_bak.list \
    && echo 'deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse\n\
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse\n\
\n\
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse\n\
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse\n\
\n\
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse\n\
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse\n\
\n\
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse\n\
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse\n\
\n\
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse\n\
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse\n'\
> /etc/apt/sources.list

还有sed，这就是自动创建配置文件的核心技术了。