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[编辑] What Is grep? （Grep是什么东西？）
Grep is a command line tool that allows you to find a string in a file or stream. It can be used with Regular expression to be more flexible at finding strings.
Grep是一个用来从文件或数据流中查找字符串的命令行工具，通过结合正则表达式Grep亦能获得更加灵活的匹配效果。
[编辑] How To Use grep （如何使用Grep）
In the simplest case, grep can simply be invoked like this :
举一个最简单的Grep使用例子：
% grep 'STRING' filename
This is OK but it does not show the true power of grep. First this only looks at one file. A cool example of using grep with multiple file would be to find all files in a directory that contains the name of a person. This can be easily accomplished using a grep in the following way :
我们可以使用Grep来简单地从一个文件中查找一个特定的字符串，但这仅仅最简单的功能而已。
% grep 'Nicolas Kassis' *
Notice the use of single quotes; This are not essential but in this example it was required since the name contains a space. Double quotes could also have been used in this example. Now lets use some regular expressions...
[编辑] Grep Regular Expression
grep can search for complicated pattern to find what you need. Here is a list of some of the special characters used to create a regular expression:
| Grep Regular Expression | ||
| ^ | <td><td>Denotes the beginning of a line （表示行开头</td><td></td>） | |
| $ | <td><td>Denotes the end of a line （表示行结尾</td><td></td>） | |
| . | <td><td>Matches any one characters （匹配任意字符</td><td></td>） | |
| * | <td><td>Matches 0 or more of the previous characters （匹配0个或多个前面出现的字符</td><td></td>） | |
| .* | <td><td>Matches any number or type of characters （匹配0或任意多个字符</td><td></td>） | |
| [] | <td><td>Matches on character for the one listed in the the Square brackets （匹配中括号中其中一个字符</td><td></td>） | |
| [^] | <td><td>Does not match any characters listed （匹配除中括号中所列字符外的所有字符</td><td></td>） | |
| \/ | <td><td>Denotes the beginning and end (respectively) of a word （匹配一个单词的开头与结尾</td><td></td>） |
So an example of a regular expression search would be
一下是一个使用了正则表达式的Grep例子
% grep "\<[A-Za-z].*" file
This will search for any word which begins with a letter upper or lower case. For more details check:
- BasicCommands
- http://www.gnu.org/software/grep/doc/
- http://en.wikipedia.org/wiki/Grep
- man grep and info grep on your computer
