Hi all,

I would like to search for 2 empty lines in a file by perl Reg Ex, how do I do that ?

Something like:

$line =~/\s\s/ ; # didn't work well.

Thanks in advance.
Mosh.

The problem with that regex is \s applies to tabs, newlines, and spaces - so this would match two spaces, or a tab followed by a space, or other undesirables. Also, I believe, perl regexes default to single line mode, so what you need is this:

$line =~ /^\n\n/m;

assuming $line contains your lines of text. The m on the end forces the regex into "multiline" mode.

The $line represents only one line...
Maybe that is the problem.

How can I make it to search for 2 blank lines in the whole file ?

What some result output do you expect when searching for 2 blank lines in a text file ? The lines number ? Also they have to be consecutive or not ?

You will need to keep a flag of some sort instead then, like this:

$flag = 0;
$line = 0;
while (<STDIN>) {
if ( /^$/ ) {
if ( $flag ) {
print "Double blank found at line: ".$line
} else {
$flag = 1;
}
} else {
$flag = 0;
}
$line++;
}

Ugh... I am not sure that the person above me's will work. Simply because your <STDIN> is asking from input from the user. I am don't think this guy is trying to get input from the keyboard. I thought it was from a file.

Whoever has the question, just post the name and the directory that the file is in, and I will write you a quick little script.

Ugh... what in thee hell is "if ( /^$/ ) {" suppose to do? If I am reading that correct, if $_ is holding nothing, then continue.

It's meant as an example, and assumes you pass the input through on STDIN - I don't know what his filename will be or how he reads it, but I've tested the script myself using a command like this:

cat file_with_blanks | /path/script.perl

In this case, the user would not be asked for input. Obviously, mosh could change it to use a different file handle, though I can't see why you'd want to write a generic script like this and then hardcode the filename. I'd think it more likely he'd want to use it on multiple files (either now or in the future). There is a semi-bug in that it will print the "double line" message twice for three blanks in a row, but it's easy to see how to get around that.


> Ugh... what in thee hell is "if ( /^$/ ) {" suppose to do? If I am reading that correct, if $_ is holding nothing, then continue.

Did you read the question? He's looking for empty lines. Geeze.

P.S: Sorry, the form ate my spaces - it does look quite ugly without some indenting.

hey cromagnon, did you try the [ code ] [ /code ] (without space) markups and put your code inside

Cheers Cedrik That will come in handy...