Sed takes a script of any number of commands followed by an optional input filespec; by default, it reads standard input.
sed接受包含任何数量命令的脚本，后面跟着可选的指定输入文件的选项；缺省情况下，它读取标准输入。
2
If your installed version supports this option, you should use it — it lets you perform swift editing operations on any given filespec with a single command.