Pattern is the regular expression used to match against the input ( usually either piped in from another program, or redirected from a text file), and replacement is the text to insert in place of the text matched by the pattern. 模式是用来匹配输入(通常可以使用管道从另一个程序输入,或者重定向于文本文件)的正则表达式,替换是指插入某些文本并用其代替那些与模式相匹配的文本。