CODEWITHSUNDEEP
regexbashvariablessed
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ogs

Reputation: 1239

Isole Ip address from dhcp-range

I would like to extract the Bcast Ip Address from dhcp-range line which is specified in the server configuration file.

dhcp-range=192.168.42.1,192.168.42.253,255.255.255.0,192.168.42.255,24h

I would like to store in a variable 192.168.42.255

Actually I am using

DNSMASQ_DIR="dnsmasq.conf"
if [ -e "$DNSMASQ_DIR" ]; then
    BcastAddress=`sed -n 3p $DNSMASQ_DIR | awk '{print $1}'`
    b=${BcastAddress:53:66}
    echo $BcastAddress
    echo $b
else
    echo "file not exists"
fi

which returns :

dhcp-range=192.168.42.1,192.168.42.253,255.255.255.0,192.168.42.255,24h
192.168.42.255,24h

I don't understand why ,24h is included. At the same time, I think that my method will be not efficient if the other IP addresses change. Is there a more efficient way to resolve my issue ?

Upvotes: 0

Views: 93

Answers (2)

Kalanidhi
Kalanidhi

Reputation: 5092

You can refer cut command also

cut -d',' -f4 dnsmasq.conf

Example :

DNSMASQ_DIR="dnsmasq.conf"
if [ -e "$DNSMASQ_DIR" ]; then
    b=`sed -n 3p $DNSMASQ_DIR | cut -d',' -f4 `
    echo $b
else
    echo "file not exists"
fi

Sed command printed 3rd line and cut command extract the 4th column delimiter of ,

Output :

192.168.42.255

Upvotes: 2

nu11p01n73R
nu11p01n73R

Reputation: 26667

If you want to do it in awk

$ echo "dhcp-range=192.168.42.1,192.168.42.253,255.255.255.0,192.168.42.255,24h" | awk -F, '{print $4}'
192.168.42.255

Simplified version of your code

You can even simplify the entire script using awk as

$ awk -F, '/^dhcp-range/{print $4}' dnsmasq.conf
192.168.42.255

  • -F, sets the field seperator as ,

  • /^dhcp-range/ selects line starting with dhcp-range

  • print $4 prints the fourth column`

OR

$ awk -F, 'NR==3{print $4}' dnsmasq.conf
192.168.42.255
  • NR==3 selects the third line

Upvotes: 1

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