sed和awk的一些命令操作

去除空格

cat a.txt | sed 's/ //g' 

显示某一行下面的所有内容
源文件

br-73908aa622e3: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 172.18.0.1  netmask 255.255.0.0  broadcast 172.18.255.255
docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:c5:14:e8:db  txqueuelen 0  (Ethernet)
        RX packets 159340  bytes 12148863 (11.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 110088  bytes 15332872 (14.6 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

显示docker0后面的的所有行数

ifconfig |sed -n '/docker0/,$p' 

[root@aliyun ~]# ifconfig |sed -n '/docker0/,$p' 
docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:c5:14:e8:db  txqueuelen 0  (Ethernet)
        RX packets 159340  bytes 12148863 (11.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 110088  bytes 15332872 (14.6 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
[root@aliyun ~]# 

显示第四行内容

ifconfig |sed -n '4p' |awk '{print $5}'