Regex to find valid IP address using awk

Question

I get all the IP address connected to the network along with strings and name of the network, but I wanted to extract only the IP's using awk regex

I tried :

awk '{match($0,/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/); ip = substr($0,RSTART,RLENGTH); print ip}'

But it prints IP address along with some numbers and date, say

2019-12-13 12
192.168.1.1
123.168.1.12
0.00012

But I want just the IP address.

`.` matches anything in regular expression. Use `\.` instead. — tsh, Dec 13 '19 at 07:05
Good that you have shown us what you are trying, it is always recommended to show your samples of input and expected output too in your question with CODE TAGS. — RavinderSingh13, Dec 13 '19 at 07:06

score 3 · Answer 1 · answered Dec 13 '19 at 07:05

3

Could you please try following. Since no samples given so didn't test it.

awk 'match($0,/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/){print substr($0,RSTART,RLENGTH)}' Input_file

Why OP's code is not working: Since OP has mentioned . in regex which is matching any character NOT literal character . that's why OP is getting results which are NOT IPs too. In above code it is escaped by doing \. which will let awk know to look for literal character . NOT for any character.

answered Dec 13 '19 at 07:05

RavinderSingh13

130,504
14
57
93

I tried with \. also but i get the same result – Jamuna Dec 13 '19 at 07:09
@Jamuna, Please do add samples in your question and let me know then? – RavinderSingh13 Dec 13 '19 at 07:12
@Jamuna, Also check 1 more thing if you have control M characters in your file by doing `cat -v Input_file` if they are there then we may need to remove them too – RavinderSingh13 Dec 13 '19 at 07:12
2

Tentative +1 for a simple(r) regex since it seems to meet OP's needs, but note that this will match nonsensical IPs such as `1234.5678.91011.1213` – Nick Reed Dec 13 '19 at 07:40

score 1 · Answer 2 · edited Dec 13 '19 at 09:07

In terms of regex, the PCRE-compatible expression (?:[12]?\d{1,2}\.){3}[12]?\d{1,2} should meet your needs. It's a simplified version of the more comprehensive IP regexes that can be found as answers on this question, and can be tested with this demo.

Unfortunately, awk is quite limited in its ability, and is not PCRE compatible. I would suggest using perl instead, but if you're insistent on using awk, the following command should work:

awk 'match($0, /[12]?[0-9]?[0-9]\.[12]?[0-9]?[0-9]\.[12]?[0-9]?[0-9]\.[12]?[0-9]?[0-9]/) {print substr($0, RSTART, RLENGTH)}'

This uses awk-compatible regex to match IPs, and is an expanded form of the above regex. It matches and prints out only the IPs it finds, omitting the rest of the line.

Before you edited your question, your original regex was 0-9]+.[0-9]+.[0-9]+.[0-9]+ - the . allowed it to match any character, meaning hyphens, spaces, and numbers were all valid matches. By specifying \. instead, the regex will exactly match the period character.

score 1 · Answer 3 · answered Dec 13 '19 at 08:35

1

to be honest, I don't have any idea about awk command, but as a good regularexp writer, to extract ip addresses , you can use this optimized exp:

/^([0-9]{0,3}\.){3}[0-9]{1,3}$/g

you can check it here : IP address Regex test

answered Dec 13 '19 at 08:35

sohaieb azaiez

768
9
20

score 0 · Answer 4 · answered Dec 13 '19 at 08:00

Something like this ?

$ cat file
172.27.1.256 # invalid ip
2019-12-13 12
192.168.1.1
123.168.1.12
0.00012
299.288.299.333 # invalid ip

$ 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]))\s+?$' file
192.168.1.1
123.168.1.12

Regex to find valid IP address using awk

4 Answers4