sed 命令不通过变量替换 ip 地址 [英] sed command not replacing ip address via variables

问题描述

我的开发环境设置要求我在/etc/host 文件中有特定的主机名到 localIP 条目.(原因是多个微服务和存储，即 Cassandra 和 Redis 绑定到主机名)我已经创建了这个简单的 bash 脚本

My development environment setup is such that it requires me to have certain host-name to localIP entry in /etc/host file .( Reason being multiple micro-services and storage i.e Cassandra and Redis bound to host-name ) I have created this simple bash script

newIP=`ip a | grep wlp5s0 | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b" | head -1`
echo $newIP
oldIP=`ping -q -c 1 -t 1 dummy | grep PING | sed -e "s/).*//" | sed -e "s/.*(//"`
echo $oldIP
sed -i 's/$oldIP/$newIP/g' /etc/hosts

虽然这打印了正确的 ip，但没有发生替换, 在我看来是 sed 的问题，但不确定

Althrough this is printing correct ip but the replacement is not happening , looks to me as an issue with sed but not sure

推荐答案

您应该按以下方式更改您的 sed 命令:

You should changed your sed command in the following way:

sed -i "s/$oldIP/$newIP/g" /etc/hosts

如果您使用简单的引号 " ' " 您的变量将不会被其值替换！

if you use simple quotes " ' " your variable will not be replaced by its value!

您还可以通过以下方式编辑您的第一个正则表达式:

You can also edit your first regex in the following way:

\b(\d{1,3}\.){3}\d{1,3}\b

最后但并非最不重要的一点是，在就地模式下使用 sed 之前，您应该备份 /etc/hosts 文件，以避免出现意外.

Last but not least, you should take a backup of your /etc/hosts file before using sed in in-place mode, to avoid bad surprises.

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