[SOLVED] sed delete multi lines after a match then do replace

Issue

I have a file /etc/config/network

config interface loopback
        option ifname   lo
        option proto    static
        option ipaddr   127.0.0.1
        option netmask  255.0.0.0

config interface lan
        option ifname   eth0
        option type     none
        option proto    static
        option ipaddr   192.168.1.1
        option netmask  255.255.255.0

config interface debug
        option ifname   usb0
        option type     none
        option proto    static
        option ipaddr   172.18.0.18
        option netmask  255.255.255.0

I want to rewrite it to be

config interface loopback
    option ifname   lo
    option proto    static
    option ipaddr   127.0.0.1
    option netmask  255.0.0.0

config interface lan
    option ifname   eth0
    option type     none
    option proto    dhcp

config interface debug
    option ifname   usb0
    option type     none
    option proto    static
    option ipaddr   172.18.0.18
    option netmask  255.255.255.0

I proceed this in this way:

1. find static then delete two lines after(exclude line static)
2. replace static with dhcp

Tried using sed '/static/{n;d}' /etc/config/network | sed -e 's/static/dhcp/' -e '/dhcp/{n;d}' > /etc/config/network which is not so neat.

Could this be like sed -i -e <delete pattern> -e <replace pattern> /etc/config/network ?

Solution

Using GNU sed

$ sed -i.bak '/config interface lan/,/^$/{/static/{N;N;s/static.*/dhcp/}}' /etc/config/network
config interface loopback
        option ifname   lo
        option proto    static
        option ipaddr   127.0.0.1
        option netmask  255.0.0.0

config interface lan
        option ifname   eth0
        option type     none
        option proto    dhcp

config interface debug
        option ifname   usb0
        option type     none
        option proto    static
        option ipaddr   172.18.0.18
        option netmask  255.255.255.0

Answered By - HatLess

Answer Checked By - Marie Seifert (WPSolving Admin)