change of ip address using perl or sed

August 4, 2022

I’ve an input file that consists of IP Address and subnet masks. As an example,

1.example.com,10.135.10.111,255.255.255.0,some comment
2.example.com,10.135.10.112,255.255.255.0,some comment
3.example.com,10.135.10.113,255.255.255.0,some comment
4.example.com,10.135.10.11,255.255.255.0, some comment
10.135.10.111 A 
10.135.10.112 A
10.135.10.113 A
10.135.10.11  A

I loop the IP address in my bash script and when using the perl or sed command all .11 gets changed. As an example:

inputip=10.135.10.11
newip=10.135.10.77

perl -i -e 's/$inputip/$newip/g' inputfile

sed -e "s/$inputip/$newip/g" inputfile

The problem is all instance of .11 gets changed. so the above record of 10.135.10.111 is changed to 10.135.10.771, .772, .773, .77

Note: this line 10.135.10.11 A is not necessarily the last line, it’s anywhere in the file.

>Solution :

Input:

$ cat inputfile
1.example.com,10.135.10.111,255.255.255.0,some comment
2.example.com,10.135.10.112,255.255.255.0,some comment
3.example.com,10.135.10.113,255.255.255.0,some comment
4.example.com,10.135.10.11,255.255.255.0, some comment
4.example.com,210.135.10.11,255.255.255.0, some comment
10.135.10.111 A
10.135.10.112 A
10.135.10.113 A
10.135.10.11  A
210.135.10.11 A

With GNU sed and word boundary flags (\< / \>):

$ inputip=10.135.10.11
$ newip=10.135.10.77
$ sed "s/\<$inputip\>/$newip/g" inputfile
1.example.com,10.135.10.111,255.255.255.0,some comment
2.example.com,10.135.10.112,255.255.255.0,some comment
3.example.com,10.135.10.113,255.255.255.0,some comment
4.example.com,10.135.10.77,255.255.255.0, some comment
4.example.com,210.135.10.11,255.255.255.0, some comment
10.135.10.111 A
10.135.10.112 A
10.135.10.113 A
10.135.10.77  A
210.135.10.11 A

If this does not work then OP is likely not using GNU sed; in this case we’d need to know what version of sed is in use (eg, sed --version).