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Re: remove single blank lines?

by Coruscate (Sexton)
on Dec 08, 2003 at 22:09 UTC ( [id://313269]=note: print w/replies, xml ) Need Help??


in reply to remove single blank lines?

I bid you welcome to the wonderful world of regular expressions (aka regexes). More information can be learned about these from perlre. Here's my version: 

my $string = q{
this
is

a
sample
text.


all single blank lines will be removed.

all double, triple, or more


blank lines will not

be touched.
};

$string =~
  s#\n(\n+)#"\n" x (length($1)>1 ? length($1)+1 : length($1))#eg;

print $string;

__END__

this
is
a
sample
text.


all single blank lines will be removed.
all double, triple, or more


blank lines will not
be touched.

[download]

Replies are listed 'Best First'.
Re: Re: remove single blank lines?
by hmerrill (Friar) on Dec 08, 2003 at 22:23 UTC
    That may work, but that regex hurts my head. The only way I would use that code is if it were commented well as to what each part of the regex does - even then I might not use it.

    A much clearer, albeit more code and more steps method, would be to: 
      1. read from the input file, and
  2. write only lines that you want to write
     to a temporary output file, and
  3. close the input file
  4. rename the temporary output file to the input file's
     name.

    [download]
    This method would allow you to read ahead one (or more than one) line to see if there are 2 more more blank lines together.

    Just my preference, but IMHO much clearer than trying to decifer that regex. My choice is to always make my code as understandable to *everyone* (including newbies) as possible. Obfuscated regex's do more to scare people away from Perl. Just my 2c.

    HTH.
[reply]
[d/l]

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