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Accepted
yael
Asked: 2012-11-16 00:27:22 +0800 CST

linux + match only VALID IP from text file into other file

  • 772

please advice how to match only the valid IPs ( 255.255.255.255 ) from the file.txt and insert only the valid IP into VALID_IP.txt file

  • ( see VALID_IP.txt for example )

the solution should be implemented in my ksh script ( so perl or sed or awk is fine also )

more file.txt

     e32)5.500.5.5*kjcdr
     ##@$1.1.1.1+++jmjh
     1.1.1.1333
     33331.1.1.1
     @5.5.5.??????
     ~3de.ede5.5.5.5
     1.1.1.13444r54
     192.9.30.174
     &&^#%5.5.5.5
     :5.5.5.5@%%^^&*
     :5.5.5.5:
     **22.22.22.22
     172.78.0.1()*5.4.3.277

example of VALID_IP.txt file

     1.1.1.1
     192.9.30.174
     5.5.5.5
     5.5.5.5
     5.5.5.5
     22.22.22.22
     172.78.0.1
linux

3 Answers

  1. Best Answer

    The following is a suitable regex, split onto 4 different lines for the sake of my own sanity.

    (1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.
(1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.
(1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])\.
(1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])

    Output:

    egrep -o `cat regex` infile #all regex lines above joined, no spaces

1.1.1.1
1.1.1.133
31.1.1.1
5.5.5.5
1.1.1.134
192.9.30.174
5.5.5.5
5.5.5.5
5.5.5.5
22.22.22.22
172.78.0.1
5.4.3.27

    Obviously this doesn't match your example. Why? Because we can't tell that that a 3 doesn't belong with a one. As you can see, garbage numbers can't be cleanly guessed at.

    • 4

  2. It's slightly cleaner with perl

    #!/usr/bin/perl
use Regexp::Common qw/net/;
while (<>) {
      print $1, "\n" if /($RE{net}{IPv4})/;
}

    but it still gets false positives 

    1.1.1.1
1.1.1.133
31.1.1.1
5.5.5.5
1.1.1.134
192.9.30.174
5.5.5.5
5.5.5.5
5.5.5.5
22.22.22.22
172.78.0.1

    Perl one liner

    perl -e 'use Regexp::Common qw/net/;while (<>) {print $1, "\n" if /($RE{net}{IPv4})/;}' infile
    • 3

  3. I recommend using range checking instead of hairy regexes. You can do this in ksh without using an external utility or another language. Although Iain's solution is nice, it's not a core module.

    Here's pure ksh. There's no need to make it a one-liner, just use a function. Code like this is easier to understand, easier to check for correctness and easier to maintain.

    #!/usr/bin/ksh
validate_ip () {
    typeset ip=$@
    typeset IFS=. valid=1
    typeset octets=($ip) octet
    typeset digits='^[[:digit:]]+$'

    if (( ${#octets[@]} == 4 ))
    then
        for ((octet = 0; octet <= 3; octet++))
        do
            value=${octets[octet]}
            if [[ ! "$value" =~ $digits ]] || ((value < 0 || value > 255))
            then
                valid=0
            fi
        done
    else
        valid=0
    fi

    if ((valid))
    then
        printf '%s\n' "$ip"
    fi

    return $valid
}

while read -r line
do
    validate_ip "$line"
done #< file.txt > VALID_IP.txt

    This is ksh 93, I haven't tested it in ksh 88. It also runs unchanged in Bash 3.2 or higher.

    • 2