Shell Programming and Scripting

I was wondering how using grep (or something else common) to find out if something was an ip address or not. Here is an example.

echo "$3"
echo "$3" | grep "[1-9]*\.[1-9]*\.[1-9]*\.[1-9]*"
[[ $(echo $3 | grep "[1-9]*\.[1-9]*\.[1-9]*\.[1-9]*") ]] && echo "IP at delim three!"

I know $3 is an IP address and only echo "$3” works but the two bottom lines don't. I need a new way of trying to verify an IP address as 1) my way doesn't work and 2) it could allow for numbers greater than 255 and thats wrong.


Also I was wondering how I would delete all spaces in a file except for ones contained between two other characters. So for example I would want:

....There ..is.. a....house....... on the ... beach.

To look like

There is a house on the beach.

Thanks in advance.

For the first one, look up "IP address regular expression" on Google. You'll find everything you could possibly want and more. This is one of the most frequently asked questions for regular expressions.

For the second one:

Code:

echo "There    is   a     house     on the      beach." | perl -pe 's/ +/ /g'

This is a Perl one-liner which replaces every instance of one or more blank spaces with a single blank space.

Note: That's a single blank space before the + symbol, and another single space in the replacement section (between the last two forward-slashes). I did it that way instead of using the \s (whitespace) symbol, because that would replace tabs and newlines, and probably produce unexpected and undesirable consequences.

ShawnMilo

I did the i'm feeling lucky with Google and found it right away. I wasn't too sure what to type in to find something like that.

Thank you so much for your quick answers.