Ubuntu – How to find out what device a file or folder is on

So here it is my comment as an answer finally: if you think about those entries in /dev as "device ids" then you have already the answer: it's maybe /dev/scd0 as you wrote. You may want to examine entires like /dev/dvd, usually udev (which manages /dev entries) creates it as a symlink for the proper device of your dvd drive. You can use than /dev/dvd with growisofs (or other tools) but for sure you can also use the entry symlink of /dev/dvd points to. As you noted too, it's nice to examine the output of command mount when your media is mounted, so you know the device name from it then!

#!/usr/bin/perl -w
use strict;

unless ( @ARGV == 1 && -f -r $ARGV[0] ) {
    die "Expected single file argument!\n";
}

my %cols;
my $ind = 0;

while (<>) {
    chomp;
    next if /^\s*($|#)/;
    ( @{ $cols{col1} }[$ind], @{ $cols{col2} }[$ind], @{ $cols{col3} }[$ind] ) = split;
    $ind++;
}

my @sorted1 = map { ${ $cols{col1} }[$_] } sort {
    ${ $cols{col1} }[$a] <=> ${ $cols{col1} }[$b] or
    ${ $cols{col2} }[$a] <=> ${ $cols{col2} }[$b] or
    ${ $cols{col3} }[$a] <=> ${ $cols{col3} }[$b]
} keys @{ $cols{col1} };
my @sorted2 = map { ${ $cols{col2} }[$_] } sort {
    ${ $cols{col1} }[$a] <=> ${ $cols{col1} }[$b] or
    ${ $cols{col2} }[$a] <=> ${ $cols{col2} }[$b] or
    ${ $cols{col3} }[$a] <=> ${ $cols{col3} }[$b]
} keys @{ $cols{col2} };

if ( "@sorted1" eq "@{ $cols{col1} }" and "@sorted2" eq "@{ $cols{col2} }") {
    print "File is sorted!\n"
}
else { print "File is unsorted!\n" };
__END__

If the columns are:

X1 Y1 Z1  
X2 Y2 Z2

Sort will be:

if (x1 > x2) then X1 Y1 Z1 > X2 Y2 Z2
if (X1 == X2) && (Y1 > Y2) then X1 Y1 Z1 > X2 Y2 Z2

To add more columns into the sort order, copy the pattern for the first two. I hope that's what you asked for.