作为一个后端开发，常常需要到服务器排查问题，翻日志啥的，，所以今天来学习 grep 的使用案例。

搜索文件内容

//单个文件
[root@yang test2]# grep test demo1.txt  
This is a test file for grep command.
The file is intended to be used for testing grep command.
// 多个文件
[root@yang test2]# grep test demo1.txt demo2.txt  
demo1.txt:This is a test file for grep command.
demo1.txt:The file is intended to be used for testing grep command.
demo2.txt:This is a test file for grep command.
demo2.txt:The file is intended to be used for testing grep command.
demo2.txt:This is another test file for grep command.
demo2.txt:The file is also intended to be used for testing grep command.
demo2.txt:This is a third test file for grep command.
demo2.txt:The file is yet another file intended for testing grep command.
// 搜索目录
[root@yang test2]# grep -r test .
./demo2.txt:This is a test file for grep command.
./demo2.txt:The file is intended to be used for testing grep command.
./demo2.txt:This is another test file for grep command.
./demo2.txt:The file is also intended to be used for testing grep command.
./demo2.txt:This is a third test file for grep command.
./demo2.txt:The file is yet another file intended for testing grep command.
./demo1.txt:This is a test file for grep command.
./demo1.txt:The file is intended to be used for testing grep command.

显示行号

[root@yang test2]# grep -n  test demo1.txt demo2.txt 
demo1.txt:1:This is a test file for grep command.
demo1.txt:4:The file is intended to be used for testing grep command.
demo2.txt:1:This is a test file for grep command.
demo2.txt:4:The file is intended to be used for testing grep command.
demo2.txt:11:This is another test file for grep command.
demo2.txt:14:The file is also intended to be used for testing grep command.
demo2.txt:21:This is a third test file for grep command.
demo2.txt:24:The file is yet another file intended for testing grep command.

搜索数字

[root@yang test2]# grep '[0-9]' demo2.txt 
This line contains the numbers 12345.
This line contains the numbers 67890.
This line contains the numbers 13579.

搜索邮箱

[root@yang test2]# grep -E '\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b' demo2.txt 
aaa@qq.com

资料：

https://www.cnblogs.com/peida/archive/2012/12/17/2821195.html