IP Address

Rails
1

Hi…

I want to check for correct ip address while i submit the form.
When i used below regular expression.it accepts 0.0.0.0 as ip address
value.
REGEXP_HOST_ADDRESS
=/\A(?:25[0-5]|(?:2[0-4]|1\d|[1-9])?\d)(?:.(?:25[0-5]|(?:2[0-4]|1\d|[1-9])?\d)){3}\z/.
But in my case it’s not a valid ip address.

so Pls help me with your assistance

2

There’s a good write-up here:

While not specific to matching an IP address, it does cover how to match
ranges like 0-255.

Regards,
Craig

3

Newb N. wrote:

so Pls help me with your assistance

I’d try breaking it up a bit, and resolving this in stages.

It looks like you’re searching for string start, expr.expr.expr.expr,
string end. The expr seems to be the same for each part, so if you solve
it once then you can use it multiple times.

The (?:slight_smile: creates a grouping without back references, which shouldn’t
change the matching pattern, so I’ll ignore it for now. This makes your
base expression

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

I think your problem is operator precedence and grouping. I’ll put in
some more parentheses and some text to indicate how this expression is
being parsed:

( (25[0-5]) or ( maybe one of these ( (2[0-4]) or (1(any digit)) or
(1-9) ) and regardless then one of any digit ) )

broken down even further:

(one of 250,251,252,253,254,255)
or
( ( ( one of 20,21,22,23,24 or one of 10,11,12,13,14,15,16,17,18,19 or
one of 1,2,3,4,5,6,7,8,9) or nothing) and 0,1,2,3,4,5,6,7,8,9)

put together, it looks like this matches everything from 0 to 255, which
means 0.0.0.0 will match when you put 4 in a row. This may be more what
you’re looking for:

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

which matches (1 to 9) or (10 to 199) or (200-249) or (250-255). If you
want to include 0 simply change the initial [1-9] to \d. E.g. matching
any IP that doesn’t start with “0.” would be:

REGEXP_HOST_ADDRESS =
/\A(?:[1-9]|1\d\d?|2[0-4]\d|25[0-5])(?:.(?:\d|1\d\d?|2[0-4]\d|25[0-5])){3}\Z/

-Chris