When comparing two files, how do I skip (ignore) blank lines? - perl

Question

I'm comparing line against line of two text files, ref.txt (reference) and log.txt. But there may be an arbitrary number of blank lines in either file that I'd like to ignore; how can I accomplish this?
ref.txt
one
two
three
end
log.txt
one
two
three
end
There would be no incorrect log lines in the output, in other words log.txt matches with ref.txt.
What I like to accomplish in pseudo code:
while (traversing both files at same time) {
if ($l is blank line || $r is blank line) {
if ($l is blank line)
skip to next non-blank line
if ($r is blank line)
skip to next non-blank line
}
#continue with line by line comparison...
}
My current code:
use strict;
use warnings;
my $logPath = ${ARGV [0]};
my $refLogPath = ${ARGV [1]} my $r; #ref log line
my $l; #log line
open INLOG, $logPath or die $!;
open INREF, $refLogPath or die $!;
while (defined($l = <INLOG>) and defined($r = <INREF>)) {
#code for skipping blank lines?
if ($l ne $r) {
print $l, "\n"; #Output incorrect line in log file
$boolRef = 0; #false==0
}
}

Answer 1

If you are on a Linux platform, use :
diff -B ref.txt log.txt
The -B option causes changes that just insert or delete blank lines to be ignored

Answer 2

You can skip blank lines by comparing it to this regular expression:
next if $line =~ /^\s*$/
This will match any white space or newline characters which can potentially make up a blank line.

Answer 3

This way seems the most "perl-like" to me. No fancy loops or anything, just slurp the files and grep out the blank lines.
use warnings;
$f1 = "path/file/1";
$f2 = "path/file/2";
open(IN1, "<$f1") or die "Cannot open file: $f1 ($!)\n";
open(IN2, "<$f2") or die "Cannot open file: $f2 ($!)\n";
chomp(#lines1 = <IN1>); # slurp the files
chomp(#lines2 = <IN2>);
#l1 = grep(!/^\s*$/,#lines1); # get the files without empty lines
#l2 = grep(!/^\s*$/,#lines2);
# something like this to print the non-matching lines
for $i (0 .. $#l1) {
print "[$f1 $i]: $l1[$i]\n[$f2 $i]: $l2[$i]\n" if($l1[$i] ne $l2[$i]);
}

Answer 4

You can loop to find each line, each time:
while(1) {
while(defined($l = <INLOG>) and $l eq "") {}
while(defined($r = <INREF>) and $r eq "") {}
if(!defined($l) or !defined($r)) {
break;
}
if($l ne $r) {
print $l, "\n";
$boolRef = 0;
}
}

Answer 5

man diff
diff -B ref.txt log.txt

Answer 6

# line skipping code
while (defined($l=<INLOG>) && $l =~ /^$/ ) {} # no-op loop exits with $l that has length
while (defined($r=<INREF>) && $r =~ /^$/ ) {} # no-op loop exits with $r that has length