Linux重定向

文件描述符-File Describtor

　　stdin　　　　0

　　stdout　　 　1

　　stderr　　　  2

重定向标准输出-redirect stdout　　>

[keysystem@localhost redirect]$ echo hello>file1
[keysystem@localhost redirect]$ echo world>file2
[keysystem@localhost redirect]$ cat file1
hello
[keysystem@localhost redirect]$ cat file2
world
[keysystem@localhost redirect]$ cat file1 >file
[keysystem@localhost redirect]$ cat file
hello
[keysystem@localhost redirect]$ cat file2 >file
[keysystem@localhost redirect]$ cat file
world
[keysystem@localhost redirect]$ cat file
file   file1  file2  
[keysystem@localhost redirect]$ cat file1 >>file
[keysystem@localhost redirect]$ cat file
world
hello
[keysystem@localhost redirect]$ cat file1 file2 >file
[keysystem@localhost redirect]$ cat file
hello
world
[keysystem@localhost redirect]$ 

重定向错误输出-redirect stdout　　2>

[keysystem@localhost redirect]$ ls shit
ls: cannot access shit: No such file or directory
[keysystem@localhost redirect]$ 
[keysystem@localhost redirect]$ ls shit >out.put
ls: cannot access shit: No such file or directory
[keysystem@localhost redirect]$ 
[keysystem@localhost redirect]$ cat out.put 
[keysystem@localhost redirect]$ ls shit 2>out.put
[keysystem@localhost redirect]$ 
[keysystem@localhost redirect]$ cat out.put 
ls: cannot access shit: No such file or directory
[keysystem@localhost redirect]$ 

重定向标准输入-redirect stdin  <

[keysystem@localhost redirect]$ cat file
hello
world
[keysystem@localhost redirect]$ 
[keysystem@localhost redirect]$ grep world <file
world
[keysystem@localhost redirect]$ 

管道命令-pipeline　　 |　

[keysystem@localhost redirect]$ cat files.txt 
d.txt
a.txt
f.html
b.txt
b.txt
[keysystem@localhost redirect]$ cat files.txt |uniq
d.txt
a.txt
f.html
b.txt
[keysystem@localhost redirect]$ cat files.txt |uniq|grep txt
d.txt
a.txt
b.txt
[keysystem@localhost redirect]$ cat files.txt |uniq|grep txt|sort
a.txt
b.txt
d.txt
[keysystem@localhost redirect]$