extra characters at the end of g command

使用sed命令替换文本内容的时候出现报错，如下

 sed -i 's/HostName/#HostName/g' /Users/gwd/.ssh/config 

sed: 1: "/Users/gwd/.ssh/config": extra characters at the end of g command

报错“sed: 1: "/Users/gwd/.ssh/config": extra characters at the end of g command”，原因在于在OS X需要显式指定扩展名，解决方案是设置一个空字符串，即执行以下命令即可

 sed -i '' 's/HostName/#HostName/g' /Users/gwd/.ssh/config