Replacing multiple blank lines with one blank line

Question

I have a file that I need to reformat and remove "extra" blank lines.

I am using the Perl syntax regular expression search and replace functionality of UltraEdit and need the regular expression to put in the "Find What:" field.

Here is a sample of the file I need to re-format.

All current text

REPLACE with all the following:


Winter 2011 Class Schedule 

Winter 2011 Class Registration Dates:  Dec. 6, 2010 – Jan. 1, 2011
Winter 2011 Class Session Dates:  Jan. 5 – Feb. 12, 2011

DANCE

Adventures in Ballet & Tap      
3 – 6 years Instructor:  Ann Newby
Tots ages 3 – 6 years old develop a greater sense of rhythm, flexibility and coordination as they explore the basic elements of movement.
Saturdays   9 - 10 a.m.     Jan. 8 – Feb. 12        Six-week fees:   $30 


African Storytelling
3 – 6 years Instructor:  Ann Newby
Tots ages 3 – 6 years old explore storytelling and fables through spoken word, music, movement and visual arts experiences.
Saturdays   10 – 11 a.m.    Jan. 8 – Feb. 12        Six-week fee:   $30


African Dance / Children

You'll notice that some of the double blank lines have spaces or tabs or both in them.

After the search and replace has been run I should have a file that looks like this.

All current text

REPLACE with all the following:

Winter 2011 Class Schedule 

Winter 2011 Class Registration Dates:  Dec. 6, 2010 – Jan. 1, 2011
Winter 2011 Class Session Dates:  Jan. 5 – Feb. 12, 2011

DANCE

Adventures in Ballet & Tap      
3 – 6 years Instructor:  Ann Newby
Tots ages 3 – 6 years old develop a greater sense of rhythm, flexibility and coordination as they explore the basic elements of movement.
Saturdays   9 - 10 a.m.     Jan. 8 – Feb. 12        Six-week fees:   $30 

African Storytelling
3 – 6 years Instructor:  Ann Newby
Tots ages 3 – 6 years old explore storytelling and fables through spoken word, music, movement and visual arts experiences.
Saturdays   10 – 11 a.m.    Jan. 8 – Feb. 12        Six-week fee:   $30

African Dance / Children

Answer 1

Should also work with spaces on blank lines

• Search - /\n^\s*\n/
• Replace - \n\n

Answer 2

On my Intellij IDE what was search for \n\n and Replace it by \n

Answer 3

See this thread for what's causing the problem. As I understand it, UltraEdit regexes are greedy at the character level (i.e., within a line), but non-greedy at the line level (roughly speaking). I don't have access to UE, but I would try writing the regex so it has to match something concrete after the last blank line. For example:

search:   (\r\n[ \t]*){2,}(\S)
replace:  $1$2

This matches and captures two or more instances of a line separator and any horizontal whitespace that follows it, but it only retains the last one. The \S should force it to keep matching until it finds a line with at least one non-whitespace character.

I admit that I don't have a whole lot of confidence in this solution; UltraEdit's regex support is crippled by its line-based architecture. If you want an editor that does regexes right, and you don't want to learn a whole new regex syntax (like vim's), get EditPadPro.

Answer 4

It depends what the line endings are. Assuming \n, replace this:

([ \t]*\n){3,}

with \n\n.