grep如何精确匹配

grep不加选项时不是精确匹配，例如：

[[email protected] ~]

# ifconfig eth0

eth0: flags=4163  mtu 1500

        inet 192.168.1.112  netmask 255.255.255.0  broadcast 192.168.1.255

        inet6 fe80::5054:ff:fe82:bc7a  prefixlen 64  scopeid 0x20

        ether 52:54:00:82:bc:7a  txqueuelen 1000  (Ethernet)

        RX packets 4219  bytes 317709 (310.2 KiB)

        RX errors 0  dropped 9  overruns 0  frame 0

        TX packets 1486  bytes 199942 (195.2 KiB)

        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[[email protected] ~]

# ifconfig eth0 | grep inet

        inet 192.168.1.112  netmask 255.255.255.0  broadcast 192.168.1.255

        inet6 fe80::5054:ff:fe82:bc7a  prefixlen 64  scopeid 0x20

怎么精确匹配只有 inet的行呢，很简单，加-w

[[email protected] ~]

# ifconfig eth0 | grep -w inet

        inet 192.168.1.112  netmask 255.255.255.0  broadcast 192.168.1.255