in reply to Sort directory by file size

Hello nnigam1, and welcome to the Monastery!

I think the problem is that the -s file test returns undef when the file is empty (i.e., when it has a zero size). One way to fix this is to test for undef and change it to zero using the // (logical defined-or) operator (see perlop#Logical-Defined-Or):

#! perl
use strict;
use warnings;

opendir D1, ...;

print "$_\n" for map  { sprintf qq[%s: %d], $_, -s $_ // 0 }
                 sort { (-s $a // 0) <=> (-s $b // 0) }
                 grep { ! -d }
                 readdir D1;

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Update: Marshall below is correct: -s returns undef only when the file does not exist. My problem was exactly as identified by choroba above: by failing to prepend the directory to the filename, I was calling -s on non-existent files. D’oh! :-(

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^2: Sort directory by file size
by Marshall (Canon) on May 18, 2016 at 16:29 UTC
    Hi Athanasius! I tested the -s operator on my Windows system with a null file (zero length). I do get a numeric 0 for a null file. Here is the test code. I did verify that 'zero' is indeed of 0 length with file manager. I think -s returns undef if the file does not exist (which is different than exists, but empty). 
    #!usr/bin/perl
use warnings;
use strict;

`copy NUL zero`;  #create empty file cp dev/null zero on unix?
my $size = -s 'zero';
print $size;      #does print "0"
__END__
0

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    Update: FYI for Windows users who don't use the command line much... NUL is a reserved word in the Windows file system for "the bit bucket". Unix folks are familiar with this concept, but sometimes Windows users aren't. someprogram > NUL does not create a file called "NUL", this just throws away STDOUT and it goes nowhere, i.e., the "bit bucket". There is no file called "NUL". To make an empty file, I copied the "bit bucket" to a file.
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