From: Brian Candler <b.candler@...>
Date: 2010-08-03T18:41:19+09:00
Subject: Re: How to remove leading   from string

> SO i entered data is like.
> ---------------------------------------------------------------
>  <p> pargraph1 pargraph1 &nbsp;&nbsp; </p>
>  <p>pargraph2 pargraph2 pargraph2 &nbsp;&nbsp; </p>
>  <p> pargraph3 hello3 hell13 &nbsp;&nbsp; </p>
>  <p> pargraph4 hello3 hell14 &nbsp;&nbsp; </p>
>  <p>&nbsp;&nbsp;&nbsp;&nbsp;</p>
> --------------------------------------------------------
> 
> In the above text 4th paragraph is the last paragrph which i 
> entered.after that i was pressed enter button so editor converted this 
> into " <p>&nbsp;&nbsp;&nbsp;&nbsp;</p"
> 
> I want to remove nbsp's after text in last paragrpah means result look 
> like
> -------------------------------------------
> <p> pargraph1 pargraph1 &nbsp;&nbsp; </p>
>  <p>pargraph2 pargraph2 pargraph2 &nbsp;&nbsp; </p>
>  <p> pargraph3 hello3 hell13 &nbsp;&nbsp; </p>
>  <p> pargraph4 hello3 hell14</p>
> ----------------------------------------------------------------

So the approach is:
(1) Write a regular expression which matches just the thing you want to 
delete;
(2) Invoke it with gsub to replace that text with the empty string.

For example, to delete *all* empty paragraphs, then you want to match 
<p> followed by any mixture of &nbsp; and space followed by </p>. So you 
could write:

    str.gsub! /<p>(&nbsp;|\s)*<\/p>/, ''

(x|y) means match x or y, \s means match any whitespace character, and * 
means match it 0 or more times.

To delete only the *last* paragraph if it is empty, then you can tweak 
it to:

    str.gsub! /<p>(&nbsp;|\s)*<\/p>\s*\z/, ''

where \z matches the end of the string, and \s* allows 0 or more space 
characters, including newlines, to precede that.

Once you're happy with that, then you can do another match and replace 
to change the final instance of "&nbsp;&nbsp; </p>" into just "</p>"

But you might want to be sure this is what you really want. How did the 
previous &nbsp; entries get there? Do you really want to keep them? It 
would be much simpler just to replace all sequences of &nbsp; or space 
with a single space.

    str.gsub! /(&nbsp;|\s)+/, ' '
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