grep简单介绍
正如linux的man文件里所描写叙述的那样：
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是用来在一个文件里查找和给定的模式相匹配的行的命令，同一时候egrep 和 fgrep都已经被弃用。取而代之的是 grep -E和grep -F。
用法
在单个文件里搜索包括字符串的行
语法：
grep “literal_string” filename
在多个文件里搜索包括字符串的行
语法：
grep “this” demo_*
注：这个的搜索域是demo_为前缀的文件
使用 -i 參数能够实现大写和小写无关
能够使用正則表達式来过滤
语法：
grep “REGEX” filename
详细用法能够參考：http://www.cnblogs.com/kuyuecs/archive/2012/07/13/2589988.html
写得非常不错的博客。