关于SED命令我就不多说了，下面奉上我的例子
在写脚本配置YUM源的时候，总是以多多益善的想法为主，所以这时候就需要制定一个模版了，下面奉上我的Centos7源的模版
[base] name=CentOS-$releasever - Base - URLS failovermethod=priority baseurl=URLS/centos/$releasever/os/$basearch/ URLS/centos/$releasever/os/$basearch/ URLS/centos/$releasever/os/$basearch/ gpgcheck=1 gpgkey=URLS/centos/RPM-GPG-KEY-CentOS-7 #released updates [updates] name=CentOS-$releasever - Updates - URLS failovermethod=priority baseurl=URLS/centos/$releasever/updates/$basearch/ URLS/centos/$releasever/updates/$basearch/ URLS/centos/$releasever/updates/$basearch/ gpgcheck=1 gpgkey=URLS/centos/RPM-GPG-KEY-CentOS-7 #additional packages that may be useful [extras] name=CentOS-$releasever - Extras - URLS failovermethod=priority baseurl=URLS/centos/$releasever/extras/$basearch/ URLS/centos/$releasever/extras/$basearch/ URLS/centos/$releasever/extras/$basearch/ gpgcheck=1 gpgkey=URLS/centos/RPM-GPG-KEY-CentOS-7 #additional packages that extend functionality of existing packages [centosplus] name=CentOS-$releasever - Plus - URLS failovermethod=priority baseurl=URLS/centos/$releasever/centosplus/$basearch/ URLS/centos/$releasever/centosplus/$basearch/ URLS/centos/$releasever/centosplus/$basearch/ gpgcheck=1 enabled=0 gpgkey=URLS/centos/RPM-GPG-KEY-CentOS-7 #contrib - packages by Centos Users [contrib] name=CentOS-$releasever - Contrib - URLS failovermethod=priority baseurl=URLS/centos/$releasever/contrib/$basearch/ URLS/centos/$releasever/contrib/$basearch/ URLS/centos/$releasever/contrib/$basearch/ gpgcheck=1 enabled=0 gpgkey=URLS/centos/RPM-GPG-KEY-CentOS-7
在这个模版中，URLS属于我预设的镜像URL可替换变量名，所以我的思路就是只需要将这个变量名替换成一个可用的URL地址即可使用该源，但是这时候谁也不知道要将这个URLS替换成什么
所以这时候就需要使用变量来解决了，一开始的想法是将不确定的URL赋值到变量U里面，然后执行下面的指令
sed "s/URLS/$U/g" dome.repo
然后提示错误了，于是我查了一下资料，得知这个SED指令可以自定义分隔符，因为 / 在shell中是有特殊的含义的，所以这时候只需要把这个符号换成其他的即可，比如#
这时候就神奇的成功了,然后试一下&
结果可见，涉及变量的时候只需要把斜杠换成其他符号即可
原文：https://www.cnblogs.com/liuyi778/p/12295161.html
