Extract lines containing range in a dhcp conf file

user_4151858 0
Viewed 41

I want to extract the lines in a file containing the range for particular subnet

Input:

subnet 172.16.31.0 netmask 255.255.255.0 {
    # default gateway
    option routers 172.16.31.10;
    option subnet-mask 255.255.255.0;

    option domain-name "aaaaaa";
    option domain-name-servers 172.16.31.10;
    #option nis-domain "domain.org";

    range dynamic-bootp 172.16.31.80 172.16.31.90;
    default-lease-time 21600;
    max-lease-time 43200;

    host test {
        hardware ethernet 00:23:8b:42:3f:d1;
        fixed-address 172.16.31.3;
    }

}
subnet 172.16.31.1 netmask 255.255.255.0 {
    # default gateway
    option routers 172.16.31.11;
    option subnet-mask 255.255.255.0;

    option domain-name "aaaaaa";
    option domain-name-servers 172.16.31.11;
    #option nis-domain "domain.org";

    range dynamic-bootp 172.16.31.80 172.16.31.90;
    default-lease-time 21600;
    max-lease-time 43200;

    host test {
        hardware ethernet 00:23:8b:42:3f:d8;
        fixed-address 172.16.31.4;
    }

}

I want to extract range dynamic-bootp for subnet 172.16.31.0.

Expected output:

range dynamic-bootp 172.16.31.80 172.16.31.90;

Is there any sed solution?

Update: Structure of the content will not be same, lines may get added / deleted based on config requirement

Tried -

sed -n '/^subnet 10.172.31.0 netmask/,/^}/{' 
    -n '  s/^\( *range dynamic-bootp\)./,/^}'
    -n '}'
    file
dhcp ipv4 shell bash
3 Answers

With GNU sed and bash:

n="172.16.31.0"
n="${n//./\\.}"  # escape every dot
sed -n '/subnet '"$n"' /,/^}/ {/range/{s/^  *//p}}' file

Update to remove leading spaces and/or tabs:

sed -n '/subnet '"$n"' /,/^}/ {/range/{s/^[[:space:]]\+//p}}' file

Output:

range dynamic-bootp 172.16.31.80 172.16.31.90;
user_37768580

Assuming input is formatted as shown (eg, a subnet block ends with a } in column 1) ...

One sed idea using a capture group (as OP appears to be attempting in the sample code):

myip='172.16.31.0'
sed -n -E "/^subnet ${myip} /,/^}/{s/.*(range dynamic-bootp[^;]*;).*/\1/p}" file

Where the capture group is defined by (range dynamic-bootp[^;]*;).

This generates:

range dynamic-bootp 172.16.31.80 172.16.31.90;
user_73661000

If your text has always that same exact structure, you could use:

grep -A9 172\.16\.31\.0 test.txt | tail -n1 | cut -d' ' -f6-

In case that the structure (amount of lines per block, spaces, etc) please add that info to the question.

user_9748220
Related