Parse a dhcpd.lease File with Bash

Question

Hi,

I Try to parse my dhcpd.lease File with Basel. A typical entry looks like this:

lease 192.168.20.4 {
    starts 6 2009/06/27 00:40:00;
    ends 6 2009/06/27 12:40:00;
    hardware ethernet 00:00:00:00:00:00;
    uid 00:00:00:00:00:00;
    client-hostname "examle-workstation1";
}

All information i get is the MAC and what i want ist the IP and the client-hostname. But maybe, there is no client-hostname. The entry looks like this:

lease 192.168.20.5 {
    starts 6 2009/06/27 00:40:00;
    ends 6 2009/06/27 12:40:00;
    hardware ethernet 00:00:00:00:00:00;
}

My first idea was to grep the lease attribute, the hardware ethernet attribute and the uid attribute and putt it all on one line. And then parse it.

But my problem is, i have a big file with many entries allocated in many files. The tree looks like this:

dhcpd-leases
-- 192.168.20.0
-- 192.168.30.0
-- 192.168.40.0
[...]

And all what i get ist the MACs parsed from another files in to a list. So i start with this list and want to grep the Attributes ip, mac with my MAC:

for ENTRY in $MACLIST
do
    VAR$(cat "dhcpd-leases/10.148.$NETWORK.2/dhcpd.leases" | grep -E "$MAC|lease|client-hostname")
    echo $VAR
done

But it because of the many entrys in the $VAR and the files im unable to Parse it out right.

Can somenone help?

Best regards Peter

Answer 1

If you are trying to get the MAC's and IP's, it would be better to use the arp -s command instead of looking at the dhcp lease file.

Hope this helps, Best regards, Tom.

Answer 2

assuming your maclist file look like this (just one entry for example)

$ cat maclist
00:00:00:00:00:01

and your lease file like this

$ cat file
lease 192.168.20.4 {
    starts 6 2009/06/27 00:40:00;
    ends 6 2009/06/27 12:40:00;
    hardware ethernet 00:00:00:00:00:00;
    uid 00:00:00:00:00:00;
    client-hostname "examle-workstation1";
}

lease 192.168.20.5 {
    starts 6 2009/06/27 00:40:00;
    ends 6 2009/06/27 12:40:00;
    hardware ethernet 00:00:00:00:00:00;
}

lease 192.168.20.6 {
    starts 6 2009/06/27 00:40:00;
    ends 6 2009/06/27 12:40:00;
    hardware ethernet 00:00:00:00:00:01;
    uid 00:00:00:00:00:01;
    client-hostname "examle-workstation2";
}


lease 192.168.20.7 {
    starts 6 2009/06/27 00:40:00;
    ends 6 2009/06/27 12:40:00;
    hardware ethernet 01:00:00:00:00:00;
}

you can try this

awk 'BEGIN{
    while( (getline line < "maclist") > 0){
        mac[line]
    }
    RS="}"
    FS="\n"
}
/lease/{
    for(i=1;i<=NF;i++){
        gsub(";","",$i)
        if ($i ~ /lease/) {
            m=split($i, IP," ")
            ip=IP[2]
        }
        if( $i ~ /hardware/ ){
            m=split($i, hw," ")
            ether=hw[3]
        }
        if ( $i ~ /client-hostname/){
            m=split($i,ch, " ")
            hostname=ch[2]
        }
        if ( $i ~ /uid/){
            m=split($i,ui, " ")
            uid=ui[2]
        }
    }
    if ( ether in mac ){
        print "ip: "ip " hostname: "hostname " ether: "ether " uid: "uid
    }
} ' file

output

$ ./shell.sh
hostname: "examle-workstation2" ether: 00:00:00:00:00:01 uid: 00:00:00:00:00:01

Answer 3

Text::DHCPLeases would also do exactly what you need, without reinventing the wheel. :)