perl - Why does readdir() list the filenames in wrong order? -

i'm using following code read filenames directory , push them onto array:

#!/usr/bin/perl  use strict; use warnings;  $directory="/var/www/out-original"; $filterstring=".csv"; @files; # open folder opendir(dir, $directory) or die "couldn't open $directory: $!\n";  foreach $filename (readdir(dir)) {     if ($filename =~ m/$filterstring/) {         # print $filename;         # print "\n";         push (@files, $filename);     }  } closedir dir;  foreach $file (@files) {     print $file . "\n"; } 

the output running code is:

report_10_2014.csv report_04_2014.csv report_07_2014.csv report_05_2014.csv report_02_2014.csv report_06_2014.csv report_03_2014.csv report_01_2014.csv report_08_2014.csv report.csv report_09_2014.csv 

why code pushing file names array in order, , not 01 10?

unix directories not stored in sorted order. unix commands ls , sh sort directory listings you, perl's opendir function not; returns items in same order kernel does, based on order they're stored in. if want results sorted, you'll need yourself:

for $filename (sort readdir(dir)) { 

(btw: bareword file handles, dir, global variables; it's considered practice use lexical file handles instead, like:

opendir $dir, $directory or die "couldn't open $directory: $!\n"; $filename (sort readdir($dir)) { 

as safety measure.)