[SOLVED] Bash Script

mrm5102 · 03-26-2012, 12:16 PM

Hello All,

Code:

MY KERNEL VERSION:
# uname -r
2.6.16.60-0.21-bigsmp

I have a bash script that takes an IP-Address as it's first argument ( i.e. "$1" ).

I setup a REGEX check to make sure that it is actually in the correct format of an IP Address. (NO IPv6).
I have it check all 4 parts of the address like so:

1st) Can be either 2 -OR- 3 digits long
2nd) Can be 1 -TO- 3 digits long
3rd) Can be 1 -TO- 3 digits long
4th) Can be 1 -TO- 3 digits long
***) All are followed by a period "."

So basically the first part must be 2 or 3 digits long and the rest can be 1 to 3 digits long. All followed by
periods, except for the final one.

Here's my REGEX check:

Code:

	shopt -s extglob
	### Check IP Address is in correct format...
	if [[ "$1" =~ ^[0-9]{2,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]
	 then
		echo "IP Address is in the correct format."
		ipAddr=$1
	fi

And I used the caret "^" and the dollar sign "$" so the match would be exact. But for some reason
if I enter the following as an IP-Address, then it passes as true... Not sure why since it is missing
a part of the address.

If I enter "192.168.1" as the IP, then it passes...? Anyone know why this is? I thought the "$" was supposed to prevent a partial match?

Any suggestions would be great.
Don't really need a different REGEX just confused and would like to know why MINE isn't doing what it should...?

Thanks in Advance,
Matt

grail · 03-26-2012, 12:58 PM

Try storing the regex in a variable with single quotes ... usually does the trick.

mrm5102 · 03-26-2012, 01:20 PM

grail,

Hey, thanks for the reply... I'll give that a try and post back.

Thanks,
Matt

mrm5102 · 03-26-2012, 01:32 PM

Hey grail,

SUCCESS!!! Great thanks for that, it worked perfectly!!

How come it needed to be in a variable..?

Thanks Again,
Matt

PTrenholme · 03-26-2012, 01:59 PM

Are you sure that the check you described will work? Wouldn't it accept 800.512.121.2 as a valid URL?

I believe that the values in the URL are intended to represent octal numbers in the 0-255 (x00-xFF) range . . .

catkin · 03-26-2012, 10:37 PM

Code:

function ck_ip_address {

    local array oIFS retval

    retval=1

    if [[ $1 =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        oIFS=$IFS
        IFS='.'
        array=( $1 )
        IFS=$oIFS
        [[ ${array[0]} -le 255 && ${array[1]} -le 255 && ${array[2]} -le 255 && ${array[3]} -le 255 ]]
        retval=$?
    fi  

    return $retval

}  # end of function ck_ip_address

grail · 03-26-2012, 11:57 PM

Quote:

How come it needed to be in a variable..?

My understanding is that some items will need to be escaped if used directly but once placed in a variable it is read in place.

A reference is here

Reuti · 03-27-2012, 06:34 AM

Just for curiosity: which version of bash are you using mrm5102? For me it’s working in the original form you posted already without any extra assignment to a variable first:

Code:

$ bash --version
GNU bash, version 3.2.39(1)-release (x86_64-suse-linux-gnu)
Copyright (C) 2007 Free Software Foundation, Inc.

David the H. · 03-27-2012, 10:43 AM

grail is basically correct above. When text is inserted directly, it is first parsed by the shell, and all shell-reserved characters have to be accounted for. This can be decidedly non-trivial to accomplish when it comes to regular expressions.

If a value is first stored in a variable, however, the value is only expanded after the majority of the parsing operations have finished. Only word-splitting and globbing take place after expansion, according to shell parsing order.

But since [[..]] is a special keyword, it doesn't do any processing of variable contents after expansion, meaning that nothing inside will be treated as special by the parser.

Thus the recommended way to handle regular expressions is to store them in a variable first. All you have to do is hard-quote the entire expression when you're setting the variable.

But remember, don't quote the variable when using it, or else the resulting string will be treated as a literal value.

mrm5102 · 04-10-2012, 10:07 AM

Hey Guys,

Sorry it seems that I must have accidentally turned off email notifications for this thread...
Thanks for the suggestions!

Reuti,
The server is running on:
bash --version
GNU bash, version 3.1.17(1)-release (i586-suse-linux)
Copyright (C) 2005 Free Software Foundation, Inc.

Thanks Again,
Matt