How to Valid IPv6 Addresses using BASH and Regex ?

IP Addresses consist of two kinds. The IPv4 and IPv6. The IPv4 is 32-bit that contains 4 bytes. For example, X.Y.Z.U where four digits (0 to 255) are separated by dots. The IPv4 contains 4294967296 (2^32) addresses. However, excluding some internal addresses such as 192.168.X.X or 127.0.0.X (local loop), it turns out that we are running out of IPv4 addresses.

IPv6 addresses, on the other hand, are 128-bits, which contains 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses (in theory, it can’ be used up, because it is more than the number of sand on earth, combined).

You will be provided with N lines of what are possibly IP addresses. You need to detect if the text contained in each of the lines represents an (a)IPv4 address (b)IPv6 address or (c)None of these.

IPv4 was the first publicly used Internet Protocol which used 4 byte addresses which permitted for 232 addresses. The typical format of an IPv4 address is A.B.C.D where A, B, C and D are Integers lying between 0 and 255 (both inclusive).

IPv6, with 128 bits was developed to permit the expansion of the address space. To quote from the linked article: The 128 bits of an IPv6 address are represented in 8 groups of 16 bits each. Each group is written as 4 hexadecimal digits and the groups are separated by colons (:). The address 2001:0db8:0000:0000:0000:ff00:0042:8329 is an example of this representation. Consecutive sections of zeros will be left as they are.
An IPv6 value such as “…:0:…” or “…:5:…” is address-wise identical to “…:0000:…” or “…:0005:….”. Leading zeros may be omitted in writing the address.

Input Format
An integer N such that N <= 50. This is followed by N lines such that each the text in each line is either an IPv4 address or an IPv6 address, or a chunk of text which does not equal either of these. There will be no extra text or whitespace leading or trailing the IP address in a line (if it is an IP address). The number of characters in each line will not exceed 500. Output Format N lines. The ith output line should equal (a)IPv4 or (b)IPv6 or (c)Neither depending on what you detected the ith input line to be. Sample Input 3 This line has junk text. 121.18.19.20 2001:0db8:0000:0000:0000:ff00:0042:8329 Sample Output Neither IPv4 IPv6

You can use

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

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

to do a simple verification for IPv4 addresses, but it does not perform checks on the maximum value for each byte. For example, the invalid address 999.999.999.999 passes the checks.

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#!/bin/bash
 
read n
for (( i=0; i<n; i++ ))
do
    read s
    if [[ $s =~ ^([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$ ]]; then
        echo IPv4
    elif [[ $s =~ ^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$ ]]; then
        echo IPv6
    else
        echo Neither
    fi
done;

#!/bin/bash

read n
for (( i=0; i<n; i++ ))
do
    read s
    if [[ $s =~ ^([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.([0-9]{1,2}|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$ ]]; then
        echo IPv4
    elif [[ $s =~ ^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$ ]]; then
        echo IPv6
    else
        echo Neither
    fi
done;

–EOF (The Ultimate Computing & Technology Blog) —