Display text file 5 lines at a time in Perl - perl

Question

I'm not sure how to do this.
I have a file (which will never be large, so won't need a module) and want to break it down so that I can display it on my web page 5 lines per row.
This is as far as I have got.
$row="5";
#DD=<DATA>;
foreach $line (#DD) {
$count++;
chomp($line);
if ($count <= $row) {
print qq~$line ~; # This shows5, but don't know what to do next.
}
}
exit;
__DATA__
aaaa
bbbb
cccc
dddd
eeee
ffff
gggg
hhhh
iiii
jjjj
kkkk
llll
mmmm
Expected result (should be in 3 line but your forum software won't let me)
aaaa bbbb cccc dddd eeee
ffff gggg hhhh iiii jjjj
kkkk llll mmmm
Could someone help please?

Answer 1

You'd have to reset the count and print a new line at 5.
print qq~$line~;
if ( $count == $row ) {
print "\n";
$count = 0;
}
else {
print ' ';
}
However, easier still is a modulus:
use strict;
use warnings;
my $row = 5;
my $count = 0;
foreach my $line ( <DATA> ) {
chomp( $line );
print $line, ++$count % $row ? ' ' : "\n";
}
If $count is a multiple of $row print a newline, else print a space.

Answer 2

When you reach the limit (5) reset the counter to 0 and print a newline
$count = 0;
print "\n";
BTW there are a number of improvements you could do to your code, but the most important would be to use strict and warnings
I think this will work:
use strict;
use warnings;
my $rows = 5;
my $count = 0;
my #lines = <DATA>;
chomp #lines;
foreach my $line (#lines) {
$count++;
if ($count <= $rows) {
print qq{$line };
} else {
$count = 0;
print "\n";
}
}

Answer 3

There are many problems with your code. See my comments below.
#!/usr/bin/env perl
use strict;
use warnings;
my $threshold = 5;
my #buffer;
while (my $line = <DATA>) {
$line =~ s/\s\z//;
push #buffer, $line;
if (#buffer % $threshold == 0) {
print join(' ', #buffer), "\n";
#buffer = ();
}
}
#buffer
and print join(' ', #buffer), "\n";
__DATA__
aaaa
bbbb
cccc
dddd
eeee
ffff
gggg
hhhh
iiii
jjjj
kkkk
llll
mmmm
Here is a list of things you should think about:
First, You should use strict and warnings.
$row="5";
$row is intended to be used as numeric variable. Why assign a string to it?
#DD=<DATA>;
foreach $line (#DD) {
No need to create an extra array by slurping, of all things, your __DATA__ section. Instead, use while and read line-by-line.
$count++;
Perl's builtin $. counts the number of lines read. No need for an additional variable.
For variety: If you insist on slurping, you can slurp into a string:
#!/usr/bin/env perl
use strict;
use warnings;
my $threshold = 5;
my $contents = do { local $/; <DATA> };
while ($contents) {
($contents, my #fields) = reverse split(qr{\n}, $contents, $threshold + 1);
print join(' ', reverse #fields), "\n";
}
or, continue to slurp into an array and use splice:
#!/usr/bin/env perl
use strict;
use warnings;
my $threshold = 5;
my #contents = <DATA>;
while (#contents) {
print join(' ', map { chomp; $_ } splice #contents, 0, $threshold), "\n";
}

Answer 4

# always start your Perl 5 files with these
# two pragmas until you know exactly why they
# are recommended
use strict;
use warnings;
my $row = 5;
while ( <> ){
chomp;
print;
print $. % $row ? ' ' : "\n";
}
# makes sure there is always a trailing newline
print "\n" if $. % $row;
$ time ./example.pl /usr/share/dict/words
...
real 0m2.217s
user 0m0.097s
sys 0m0.084s
In Perl 6 I would probably write it as:
'filename'.IO.lines.rotor(5, :partial).map: *.say;
( currently takes about 15 seconds to process /usr/share/dict/words under the Moar backend, but it hasn't had 20 years of optimizations applied to it like Perl 5 has. It may be faster with the JVM backend )