前面学习的grep都是最基本的unix GREP语法，但是LINUX GREP是GNU GREP，基本语法相同，但是扩展了这些语法，特别是正则表达式，LINUX 在grep命令选项中可以通过一些参数来确定不同的正则表达式格式。
从上面表达式中可以看出，实际上如grep –E 就相当于egrep， grep –F 就相当于fgrep，最后一种是perl 正则，这个比较特殊一点。Linux Grep缺省情况下比GNU Grep会支持如下三种正则表达式：
| \w | 词字符标志，也就是大小写加上数字和下划线 | |\w*e | 在字符|后面跟上零到多个词字符，并在后面跟上e如love, le,l9e |
| \W | 非词字符标志，也就是除大小写数字及下划线之外 | \W\w* | 匹配一个非词字符，并且后面跟上零或者多个词字符 |
| \b | 字边界等于\< \>，也等于-w 选项 | \blove\b | 匹配单词love |
[windriver@windriver-machine ltest]$ grep '^b\w*\W' datafile
[windriver@windriver-machine ltest]$ grep '^n\w*\W' datafile northwest NW Charles Main 3.0 .90 3 34 northeast NE AM Main Jr. 5.1 .94 3 13 north NO Margot Weber 4.5 .89 5 9 [windriver@windriver-machine ltest]$ grep '^[a-z]\w*\W' datafile northwest NW Charles Main 3.0 .90 3 34 western WE Sharon Gray 5.3 .97 5 23 southwest SW Lewis Dalsass 2.7 .8 2 18 southern SO Suan chin 5.1 .95 4 15 southeast SE Patricia 4.0 .7 4 17 eastern EA TB Savage 4.4 .84 5 20 northeast NE AM Main Jr. 5.1 .94 3 13 north NO Margot Weber 4.5 .89 5 9 central CT Ann Stephens 5.7 .94 5 13 [windriver@windriver-machine ltest]$ grep '\bnorth\b' datafile north NO Margot Weber 4.5 .89 5 9 [windriver@windriver-machine ltest]$ grep '\<north\>' datafile north NO Margot Weber 4.5 .89 5 9 [windriver@windriver-machine ltest]$[windriver@windriver-machine ltest]$ grep 'NW|EA' datafile
[windriver@windriver-machine ltest]$ egrep 'NW|EA' datafile northwest NW Charles Main 3.0 .90 3 34 eastern EA TB Savage 4.4 .84 5 20 [windriver@windriver-machine ltest]$ grep -E 'NW|EA' datafile northwest NW Charles Main 3.0 .90 3 34 eastern EA TB Savage 4.4 .84 5 20 [windriver@windriver-machine ltest]$ grep -E 'NW\|EA' datafile [windriver@windriver-machine ltest]$ grep 'NW\|EA' datafile northwest NW Charles Main 3.0 .90 3 34 eastern EA TB Savage 4.4 .84 5 20 [windriver@windriver-machine ltest]$ grep -E '3+' datafile northwest NW Charles Main 3.0 .90 3 34 western WE Sharon Gray 5.3 .97 5 23 northeast NE AM Main Jr. 5.1 .94 3 13 central CT Ann Stephens 5.7 .94 5 13 [windriver@windriver-machine ltest]$ egrep '3+' datafile northwest NW Charles Main 3.0 .90 3 34 western WE Sharon Gray 5.3 .97 5 23 northeast NE AM Main Jr. 5.1 .94 3 13 central CT Ann Stephens 5.7 .94 5 13 [windriver@windriver-machine ltest]$ grep '3\+' datafile northwest NW Charles Main 3.0 .90 3 34 western WE Sharon Gray 5.3 .97 5 23 northeast NE AM Main Jr. 5.1 .94 3 13 central CT Ann Stephens 5.7 .94 5 13 [windriver@windriver-machine ltest]$ egrep '2\.?[0-9]' datafile western WE Sharon Gray 5.3 .97 5 23 southwest SW Lewis Dalsass 2.7 .8 2 18 eastern EA TB Savage 4.4 .84 5 20 [windriver@windriver-machine ltest]$从上面我们还可以看出一个功能，就是Egrep扩展的一些的元字符，如用grep时如何用这些元字符呢，可以使用\进行转义，一下子就变成了EGREP，相当于grep –E.
grep 还有一个选项是遍历文件目录，grep –r ,有些LINUX提供了rgrep。还有一些其它选项，可以使用man来提示。
[windriver@windriver-machine ltest]$ grep -V
grep (GNU grep) 2.5.1Copyright 1988, 1992-1999, 2000, 2001 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.[windriver@windriver-machine ltest]$ man grep
[windriver@windriver-machine ltest]$ man grep [windriver@windriver-machine ltest]$ grep -A datafile grep: datafile: invalid context length argument[windriver@windriver-machine ltest]$ grep -A 'Nw' datafile
grep: Nw: invalid context length argument[windriver@windriver-machine ltest]$ grep -A 2 'NW' datafile
northwest NW Charles Main 3.0 .90 3 34 western WE Sharon Gray 5.3 .97 5 23 southwest SW Lewis Dalsass 2.7 .8 2 18 [windriver@windriver-machine ltest]$ grep -A 1 'NW' datafile northwest NW Charles Main 3.0 .90 3 34 western WE Sharon Gray 5.3 .97 5 23 [windriver@windriver-machine ltest]$ grep -A 0 'NW' datafile northwest NW Charles Main 3.0 .90 3 34 [windriver@windriver-machine ltest]$ grep -B 0 'NW' datafile northwest NW Charles Main 3.0 .90 3 34 [windriver@windriver-machine ltest]$ grep -B 1 'NW' datafile northwest NW Charles Main 3.0 .90 3 34 [windriver@windriver-machine ltest]$ man grep [windriver@windriver-machine ltest]$