#!/bin/bash
tempFileName=${1:-file}

    awkExtractIPAddresses='
    BEGIN {
        ipSequence = "[0-9]+[.][0-9]+[.][0-9]+[.][0-9]+"
        digitSequenceTooLongNotIP = "[0-9][0-9][0-9][0-9]+"
        encInFwdSlashesNotIP = "[/]" ipSequence "[/]"
        versioningNotIP = "[Vv]([Ee][Rr]([Ss][Ii][Oo][Nn])?)?[ .]*" ipSequence
    }
    {
        line = $0
        gsub(digitSequenceTooLongNotIP, "x", line)
        gsub(encInFwdSlashesNotIP, "x", line)
        gsub(versioningNotIP, "x", line)
        while (match(line, ipSequence)) {
            ip = substr(line, RSTART, RLENGTH)
            ipUnique[ip]
            line = substr(line, RSTART + RLENGTH + 1)
        }
    }
    END {
        ipRangeMin = 0
        ipRangeMax = 255
        ipNumSegments = 4
        ipDelimiter = "."
        for (ip in ipUnique) {
            numSegments = split(ip, ipSegments, ipDelimiter)
            if (numSegments == ipNumSegments &&
                ipSegments[1] >= ipRangeMin && ipSegments[1] <= ipRangeMax &&
                ipSegments[2] >= ipRangeMin && ipSegments[2] <= ipRangeMax &&
                ipSegments[3] >= ipRangeMin && ipSegments[3] <= ipRangeMax &&
                ipSegments[4] >= ipRangeMin && ipSegments[4] <= ipRangeMax) {
                    print ip
            }
        }
    }'

    ipAddressMatches=$(awk "$awkExtractIPAddresses" "$tempFileName")

printf "%s\n" $ipAddressMatches

# test_data
This is a valid IP address 192.168.1.1
This is not valid 111.222.333.444 some values are out of range.
This is way off: 1.2.3.4.5.6
This is a version 1.2.1.2 number in the same form as an IP.
This is a version number inside an url http://web.com/lib/1.2.3.4/file.js
This is another valid IP but in some CSS <ip>192.168.1.2</ip>
This is one with a too long digit sequence 192.16888.1.3
This is a final valid IP 192.168.1.3 just for luck.

BEGIN {
    ipLikeSequence = "[0-9]+[.][0-9]+[.][0-9]+[.][0-9]+[0-9.]*";
    digitSequenceTooLongNotIP = "[0-9][0-9][0-9][0-9]+";
    versioningNotIP = "[Vv]([Ee][Rr]([Ss][Ii][Oo][Nn])?)?[ .:]*" ipLikeSequence;
    enclosedInFwdSlashesNotIP = "[/]" ipLikeSequence "[/]";
    beginsWithFwdSlashNotIP = "[/]" ipLikeSequence;
    endsWithFwdSlashNotIP = ipLikeSequence "[/]";
}
{
    line = $0;

    gsub(digitSequenceTooLongNotIP, "x", line);
    gsub(versioningNotIP, "x", line);
    gsub(enclosedInFwdSlashesNotIP, "x", line);
    gsub(beginsWithFwdSlashNotIP, "x", line);
    gsub(endsWithFwdSlashNotIP, "x", line);

    while (match(line, ipLikeSequence))
    {
        ip = substr(line, RSTART, RLENGTH);
        ipUnique[ip] = ip;
        # ipUnique[ip];
        line = substr(line, RSTART + RLENGTH + 1);
        printf("Storing possible IP address: %s\n", ip);
    }
}
END {
    ipRangeMin = 0;
    ipRangeMax = 255;
    ipNumSegments = 4;
    ipDelimiter = ".";

    for (ip in ipUnique)
    {
        numSegments = split(ip, ipSegments, ipDelimiter);
        if (numSegments == ipNumSegments &&
            ipSegments[1] >= ipRangeMin && ipSegments[1] <= ipRangeMax &&
            ipSegments[2] >= ipRangeMin && ipSegments[2] <= ipRangeMax &&
            ipSegments[3] >= ipRangeMin && ipSegments[3] <= ipRangeMax &&
            ipSegments[4] >= ipRangeMin && ipSegments[4] <= ipRangeMax)
        {
            printf("Valid IP:   %s\n", ip);
        }
        else
        {
            printf("Invalid IP: %s\n", ip);
        }
    }
}

$ awk -f test.awk < test_data
Storing possible IP address: 192.168.1.1
Storing possible IP address: 111.222.333.444
Storing possible IP address: 1.2.3.4.5.6
Storing possible IP address: 192.168.1.2
Storing possible IP address: 192.168.1.3
Invalid IP: 1.2.3.4.5.6
Valid IP:   192.168.1.1
Valid IP:   192.168.1.2
Valid IP:   192.168.1.3
Invalid IP: 111.222.333.444

# Swap "ipUnique[ip] = ip;" for "ipUnique[ip];" in test.awk

$ awk -f test.awk < test_data
Storing possible IP address: 192.168.1.1
Storing possible IP address: 111.222.333.444
Storing possible IP address: 1.2.3.4.5.6
Storing possible IP address: 192.168.1.2
Storing possible IP address: 192.168.1.3
Invalid IP: 1.2.3.4.5.6
Valid IP:   192.168.1.1
Valid IP:   192.168.1.2
Valid IP:   192.168.1.3
Invalid IP: 111.222.333.444