delete empty line?

[Anon]

I'm not good at regular expression. What are the ways to delete empty lines? Such as:
$aaa = " LINE 1
LINE 2

LINE n";

Output should be :
$aaa = " LINE 1
LINE 2
LINE n";
Thanks.

[Anon]

There's two answers depending on whether or not you count lines with only spaces and tabs as "empty".

If you don't (that is, you distinguish between "empty" and "blank") then

$aaa=preg_replace("/\n\n+/","\n",$aaa);

will do the job.

If, on the other hand, you want to get of blank lines as well,

$aaa=preg_replace("/\n\s*?\n+/","\n",$aaa);

and the "\s*" will match such (possible) whitespace.

Of course, this assumes that newlines aren't Windows newlines. If they might be, then the two regexps become

/\r?\n(\r?\n)+/
and
/\r?\n)\s*?(\r?\n)+/

respectively.

[Anon]

what do you mean by Windows newlines?

[Anon]

On Windows systems, text file newlines are represented by two characters - "\r\n", meaning "carriage return, newline" like on typewriters.

Unix systems just use the newline "\n".

Depending on where your text is coming from (if a Windows machine is involved), it may be using the characters \r\n at the end of every line. So to strip out empty lines in Windows-style text, you have to match "\r\n" instead of just "\n".

One of Microsoft's less-clever ideas, I thought.

[[deleted]]

Not Microsoft's idea, CP/M and older OS's derived from the original teletype driven mainframes.

Just as strange is Apple's use of \r in text files. 🙂

[Anon]

Okay; Yeah, MS-DOS was a rebranding of Pacific's Quick-and-Dirty OS, which was a single-user kludge of CP/M. I wasn't quite aware that the \r\n thing had been around that long.

But that still doesn't excuse Microsoft from not not dropping the silliness when they had the chance.