grep简介

正如linux的man文件中所描述的那样：

   grep  searches  the  named  input  FILEs (or standard input if no files are named, or if a single hyphen-minus (-) is given as file name) for lines containing a match to the given PATTERN.  By default, grep prints the matching lines.
   In addition, two variant programs egrep and fgrep are available.  egrep is the same as grep -E.   fgrep  is  the  same  as  grep -F.   Direct invocation as either egrep or fgrep is deprecated, but is provided to allow historical applications that rely on them to run unmodified.

grep是用来在一个文件中查找和给定的模式相匹配的行的命令，同时egrep 和 fgrep都已经被弃用，取而代之的是 grep -E和grep -F。

使用方法

在单个文件中搜索包含字符串的行

语法：
grep “literal_string” filename

在多个文件中搜索包含字符串的行

语法：
grep “this” demo_*
注：这个的搜索域是demo_为前缀的文件

使用 -i 参数可以实现大小写无关

可以使用正则表达式来过滤

语法：
grep “REGEX” filename

具体使用方法可以参考：http://www.cnblogs.com/kuyuecs/archive/2012/07/13/2589988.html
写得很不错的博客。