Get only the address part of NIC (eth0)

Network address

If you display the ip with ifconfig, you can get the ip of multiple NICs. For example, it looks like the following. Think about how to get the NIC address of eth0 with ifconfig.

$ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.28.99.150  netmask 255.255.240.0  broadcast 172.28.111.255
        inet6 fe80::215:5dff:xxx:xxxx  prefixlen 64  scopeid 0x20<link>
        ether 00:15:5d:90:90:41  txqueuelen 1000  (Ethernet)
        RX packets 742  bytes 149376 (149.3 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 16  bytes 1216 (1.2 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Grep the address of eth0

To gerp with ifconfig and get only the IP address, do as follows.

ifconfig eth0 | grep -oP '(?<=inet\s)\d+(\.\d+){3}'

Display the information of the NIC you want to get with ifcongit eth0. If you want to get the IP address of another NIC, specify the number like ethXX. (Is this the case ...) Then I pipe the result and grep it with a regular expression. o is an option to take only the matches, P is a Perl-style regular expression, With this combination, you can create a part where row extraction and clipping match.

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