Generate networking configuration files using sed and bash

Question

I am a bit rusty on my scripting abilities and am trying to find a good starting point for creating a script that creates files (generating new file names) and edits the IP address in the file by incrementing it by +1

My scenario is like so - We have about 50 IP addresses to add to our network-scripts each with an incrementing IP. I could do this by hand, however I thought this would be a good time to try and get up to speed on my scripting skills.

The naming scheme is like so:

ifcfg-eth0:1, ifcfg-eth0:2, ifcfg-eth0:3 ...*n*

The content of these files is:

DEVICE=eth0:1 NETMASK=255.255.255.0 IPADDR=10.2.7.148 BOOTPROTO=none ONBOOT=yes DNS1=10.2.53.150 PEERDNS=yes DNS2=10.2.53.250 GATEWAY=10.2.7.1 TYPE=Ethernet USERCTL=no IPV6INIT=no 

Where IPADDR=10.2.7.148 should be increased by +1 in each file.

For example: ifcfg-eth0:2 file would be the exact same except that the IPADDR would be 10.2.7.149 and so on.

I am fairly certain I should invoke sed to find and replace the IP addresses.

For instance, searching for an IP address using sed could be accomplished like so:

sed -rn '/(IPPADDR=)((1?[0-9][0-9]?|2[0-4][0-9]|25[0-5])\.){3}(1?[0-9][0-9]?|2[0-4][0-9]|25[0-5])/p' file 

What steps need to be taken to generate a new file with the eth0:N name incremented by +1 as well as the IP address in the file.

Thanks in advance!

EDIT: Let me clarify the names of the files should not contain the IP address.

I am needing file1 to be copied over to file2 eth0:1 ->eth0:2 with same file contents as above, except the fact that the IPADDR= field on the generated file should be incremented by one.

Note: The file name should also be incremented by +1 IE. cp ifcfg-eth0:1 ifcfg-eth0:2

Answer 1

As far as I'm aware of sed cannot do calculations on numbers, I would use awk

$ awk -F'.' '$1~"IPADDR"{$NF++;OFS="."}1' file DEVICE=eth0:1 NETMASK=255.255.255.0 IPADDR=10.2.7.149 BOOTPROTO=none ONBOOT=yes DNS1=10.2.53.150 PEERDNS=yes DNS2=10.2.53.250 GATEWAY=10.2.7.1 TYPE=Ethernet USERCTL=no IPV6INIT=no 

Include this into a loop of files to be changed.

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Explanation:

• -F'.': use . a field separator
• $1~"IPADDR"{}: if first field contains IPADDR pattern run what is inside{}
• $NF++;OFS=".": increment number in last field (NF denotes number of fields in the record).
• 1: print everything

Answer 2

I don't know if I've understood you correctly. Does this do what you want?

Bash:

[root@domain]:test # IP=120 [root@domain]:test # for i in {1..50}; do > echo "IP=10.11.11.$IP > NETMASK=255.255.255.0 > DEVICE=eth0:1 > ONBOOT=yes > DNS1=10.2.53.150 > PEERDNS=yes > DNS2=10.2.53.250 > GATEWAY=10.2.7.1 > TYPE=Ethernet > USERCTL=no > IPV6INIT=no" >> ifcfg-eth0:$i; IP=$((IP+1)); done; 

Result:

[root@domain]:test # ls ifcfg* |wc -l 50 [root@domain]:test # grep IP= ifcfg* ifcfg-eth0:1:IP=10.11.11.120 ... ifcfg-eth0:50:IP=10.11.11.169 

Answer 3

With perl :

$ perl -ne ' s/^(IPADDR=10\.2\.7\.)(\d+)/$2 < 255 and sprintf "%s%s", $1, $2 + 1/e; print ' file 

Output:

DEVICE=eth0:1 NETMASK=255.255.255.0 IPADDR=10.2.7.149 BOOTPROTO=none ONBOOT=yes DNS1=10.2.53.150 PEERDNS=yes DNS2=10.2.53.250 GATEWAY=10.2.7.1 TYPE=Ethernet USERCTL=no IPV6INIT=no 

You can add -i switch to modify the file in-place.