linux 重定向与管道

一：重定向

1. 输入重定向（真不知道有什么卵用）

2. 输出重定向

‘>(覆盖)’ ：把原本输出到屏幕的信息输出到其他地方

[xxjqr@localhost Desktop]$ cat test2.txt 
this is test2 file
[xxjqr@localhost Desktop]$ touch test.txt
[xxjqr@localhost Desktop]$ cat test2.txt > test.txt 
[xxjqr@localhost Desktop]$ cat test.txt 
this is test2 file
[xxjqr@localhost Desktop]$ 

'>>(追加)'

二：管道

管道其实就是一个连接符，把上一条命令的输出当作此条命令的输入

[xxjqr@localhost Desktop]$ cat test.txt 
This is first line
This is second line
This is third line
[xxjqr@localhost Desktop]$ cat test.txt | grep third
This is third line
[xxjqr@localhost Desktop]$ 

管道实例

[root@localhost Desktop]# cat /etc/passwd | grep root #查看是否存在指定账户
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin
[root@localhost Desktop]# dmesg | grep eth0 #查看第一块网卡信息
e1000 0000:02:01.0: eth0: (PCI:66MHz:32-bit) 00:0c:29:a1:49:1e
e1000 0000:02:01.0: eth0: Intel(R) PRO/1000 Network Connection
ADDRCONF(NETDEV_UP): eth0: link is not ready
8021q: adding VLAN 0 to HW filter on device eth0
e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
eth0: no IPv6 routers present
e1000: eth0 NIC Link is Down
e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
[root@localhost Desktop]# rpm -qa | grep httpd #查看是否安装了apache软件
httpd-2.2.15-53.el6.centos.x86_64
httpd-tools-2.2.15-53.el6.centos.x86_64