CODEWITHSUNDEEP
perl
rjzii
rjzii

Reputation: 14533

How do I split on every other line?

I am working on a Perl script that processes the output from ec2-describe-instances which is returning its output as follows:

INSTANCE\n
TAG\n
INSTANCE\n
TAG\n
INSTANCE\n
TAG\n

Is there a way that I can use the split function so that the results are split into two line chunks such as the following?

INSTANCE\n
TAG\n

Upvotes: 0

Views: 176

Answers (1)

ikegami
ikegami

Reputation: 385655

The first arg of split should be what separates what you wanted returned.

split /(?!^)(?=(?:.*\n.*\n)+\z)/, do { local $/; <> };

But that's very inefficient.

If you want to output to a handle, you could use:

perl -pe'()=split//,""; print "\n" if $. % 2 == 1 && $. > 1'

Which is similar to:

()=split//,"";
while (<>) {
    print "\n" if $. % 2 == 1 && $. > 1;
    print;
}

(I strongly recommend leaving out the ()=split//,"";.)

$. the line number of the last line read.

If you want to output to an array, you could use:

()=split//,""; 
my @array;
my $buf;
while (<>) {
   $buf .= $_;
   if ($. % 2 == 1) {
      push @array, $buf;
      $buf = '';
   }
}

(I strongly recommend leaving out the ()=split//,"";.)

If you're ok with loading everything into memory, you could use

()=split//,"";
my @array = do { local $/; <> } =~ /\G.*\n.*\n/g;

(I strongly recommend leaving out the ()=split//,"";.)

Upvotes: 1

Related Questions