2

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
Improve this question

3 Answers 3

Reset to default
4

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.

Improve this answer
6
  • but how to add this to my ksh script ? Commented Nov 15, 2012 at 8:51
  • @yael use egrep -o Commented Nov 15, 2012 at 9:03
  • 1
    If you use grep -oP you can use look-around constraints to limit the invalid first and last octets: grep -oP '(?<!\d)(1?\d?\d|2[0-4]\d|25[0-5])(\.(1?\d?\d|2[0-4]\d|25[0-5])){3}(?!\d)' Commented Nov 15, 2012 at 12:28
  • @glennjackman Good point. It didn't click to me that none of the "extra digits" numbers were included in the example output, probably from a combination of it being very late at night my time and the syntax highlighting. Definitely should use negations in this circumstance, yet be aware that one extra digit of nonsense could still make a valid IP depending on the digit. Commented Nov 15, 2012 at 22:56
  • @Jeff your solution is fine for linux but the egrep flag for solaris is diffrent , can you please advice what the same solution for solaris machines ? Commented Nov 18, 2012 at 6:48
3

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
Improve this answer
4
  • is it possible to translate this perl script to one perl line so I will add this to my ksh script ? Commented Nov 15, 2012 at 9:50
  • @yael: see my edit Commented Nov 15, 2012 at 10:39
  • Use lookaround assertions to eliminate the false positives: /(?<!\d)($RE{net}{IPv4})(?!\d)/ Commented Nov 15, 2012 at 12:30
  • In fact, can tighten up the one-liner: perl -MRegexp::Common=net -lne 'print for /(?<!\d)($RE{net}{IPv4})(?!\d)/' Commented Nov 15, 2012 at 14:20
2

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.

Improve this answer

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.