sed - How to extract IP address using sed?

Question

This is for an assignment so I have no choice but to use sed.

Given a file messages, how can I extract all the IP addresses and print them?

I first

Answer 1

Use sed -r (extended regex) or escape the capture groups with \

Answer 2

You can do that too:

Windows:

ipconfig | perl -nle'/(\d+\.\d+\.\d+\.\d+)/ && print $1' | sed '2 d' | head -n1;

OSX:

ifconfig | perl -nle'/(\d+\.\d+\.\d+\.\d+)/ && print $1' | sed '1 d' | head -n1;

Answer 3

If you have GNU sed, you could simply add the -r flag to use EREs:

sed -rn '/((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

Otherwise, you will need to escape certain characters:

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

These characters include:

• groups using parenthesis: (, )
• occurrence braces: {, }
• 'or' pipes: |
• non-greedy question marks: ?

Generally (although not for your case) I use the following to match IP address:

sed -rn '/([0-9]{1,3}\.){3}[0-9]{1,3}/p' file

Or in compatibility mode:

sed -n '/\([0-9]\{1,3\}\.\)\{3\}[0-9]\{1,3\}/p' file

Answer 4

grep will be more suitable there (if you have sed, you should have grep too):

grep -oE '((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])' messages

This is your own regex with no modification (tested OK)

Answer 5

If you use git-bash on Windows. It is quite handy.

 export LC_ALL=C; ipconfig | sed -n 's/IPv4//gp;' | sed -En 's/.*(10.*)/\1/gp' 

以太网适配器 VMware Network Adapter VMnet1:

   连接特定的 DNS 后缀 . . . . . . . :
   本地链接 IPv6 地址. . . . . . . . : fe80::3177:bf7b:590:c787%6
   IPv4 地址 . . . . . . . . . . . . : 192.168.31.1
   子网掩码  . . . . . . . . . . . . : 255.255.255.0
   默认网关. . . . . . . . . . . . . :

以太网适配器 VMware Network Adapter VMnet8:

   连接特定的 DNS 后缀 . . . . . . . :
   本地链接 IPv6 地址. . . . . . . . : fe80::c8de:747e:34fe:58cd%12
   IPv4 地址 . . . . . . . . . . . . : 192.168.239.1
   子网掩码  . . . . . . . . . . . . : 255.255.255.0
   默认网关. . . . . . . . . . . . . :

以太网适配器 以太网:

   连接特定的 DNS 后缀 . . . . . . . : some.com
   本地链接 IPv6 地址. . . . . . . . : fe80::9d9:bb4d:e77a:3a98%15
   IPv4 地址 . . . . . . . . . . . . : 10.11.68.42
   子网掩码  . . . . . . . . . . . . : 255.255.254.0
   默认网关. . . . . . . . . . . . . : 10.11.168.1

The script will only give you the 10 prefixed ip address 10.11.68.42.

The script can be explained to be

match lines contain IPv4 and substitute IPv4 with blank and print, then capture something prefixed with 10 and print it