How to sort by file name the same way Windows Explorer does?

Question

Here is some very short code (just the $ToNatural script block) that does the trick with a regular expression and a match evaluator in order to pad the numbers with spaces. Then we sort the input with padded numbers as usual and actually get natural order as a result.

$ToNatural = { [regex]::Replace($_, '\d+', { $args[0].Value.PadLeft(20) }) }

'----- test 1 ASCIIbetical order'
Get-Content list.txt | Sort-Object

'----- test 2 input with padded numbers'
Get-Content list.txt | %{ . $ToNatural }

'----- test 3 Natural order: sorted with padded numbers'
Get-Content list.txt | Sort-Object $ToNatural

Output:

----- test 1 ASCIIbetical order
1.txt
10.txt
3.txt
a10b1.txt
a1b1.txt
a2b1.txt
a2b11.txt
a2b2.txt
b1.txt
b10.txt
b2.txt
----- test 2 input with padded numbers
                   1.txt
                  10.txt
                   3.txt
a                  10b                   1.txt
a                   1b                   1.txt
a                   2b                   1.txt
a                   2b                  11.txt
a                   2b                   2.txt
b                   1.txt
b                  10.txt
b                   2.txt
----- test 3 Natural order: sorted with padded numbers
1.txt
3.txt
10.txt
a1b1.txt
a2b1.txt
a2b2.txt
a2b11.txt
a10b1.txt
b1.txt
b2.txt
b10.txt

And finally we use this one-liner to sort files by names in natural order:

Get-ChildItem | Sort-Object { [regex]::Replace($_.Name, '\d+', { $args[0].Value.PadLeft(20) }) }

Output:

    Directory: C:\TEMP\_110325_063356

Mode                LastWriteTime     Length Name                                                                                                                  
----                -------------     ------ ----                                                                                                                  
-a---        2011-03-25     06:34          8 1.txt                                                                                                                 
-a---        2011-03-25     06:34          8 3.txt                                                                                                                 
-a---        2011-03-25     06:34          8 10.txt                                                                                                                
-a---        2011-03-25     06:34          8 a1b1.txt                                                                                                              
-a---        2011-03-25     06:34          8 a2b1.txt                                                                                                              
-a---        2011-03-25     06:34          8 a2b2.txt                                                                                                              
-a---        2011-03-25     06:34          8 a2b11.txt                                                                                                             
-a---        2011-03-25     06:34          8 a10b1.txt                                                                                                             
-a---        2011-03-25     06:34          8 b1.txt                                                                                                                
-a---        2011-03-25     06:34          8 b2.txt                                                                                                                
-a---        2011-03-25     06:34          8 b10.txt                                                                                                               
-a---        2011-03-25     04:54         99 list.txt                                                                                                              
-a---        2011-03-25     06:05        346 sort-natural.ps1                                                                                                      
-a---        2011-03-25     06:35         96 test.ps1                                                                                                              

Allow me to copy and paste my answer from another question.

Powershell Sort-Object Name with numbers doesn't properly

Windows explorer is using a legacy API from shlwapi.dll which called StrCmpLogicalW, that's the reason seeing different sorting results.

I don't want to pad zeros, so wrote a script.

https://github.com/LarrysGIT/Powershell-Natural-sort

Since I am not a C# expert, pull requests are appreciated if it's not tidy.

Find following PowerShell script, it uses the same API.

function Sort-Naturally
{
    PARAM(
        [System.Collections.ArrayList]$Array,
        [switch]$Descending
    )

    Add-Type -TypeDefinition @'
using System;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;
namespace NaturalSort {
    public static class NaturalSort
    {
        [DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
        public static extern int StrCmpLogicalW(string psz1, string psz2);
        public static System.Collections.ArrayList Sort(System.Collections.ArrayList foo)
        {
            foo.Sort(new NaturalStringComparer());
            return foo;
        }
    }
    public class NaturalStringComparer : IComparer
    {
        public int Compare(object x, object y)
        {
            return NaturalSort.StrCmpLogicalW(x.ToString(), y.ToString());
        }
    }
}
'@
    $Array.Sort((New-Object NaturalSort.NaturalStringComparer))
    if($Descending)
    {
        $Array.Reverse()
    }
    return $Array
}

Find test results below.

PS> # Natural sort
PS> . .\NaturalSort.ps1
PS> Sort-Naturally -Array @('2', '1', '11')
1
2
11
PS> # If regular sort is being used
PS> @('2', '1', '11') | Sort-Object
1
11
2

PS> # Not good
PS> $t = ls .\testfiles\*.txt
PS> $t | Sort-Object
1.txt
10.txt
2.txt

PS> # Good
PS> Sort-Naturally -Array $t
1.txt
2.txt
10.txt

Translation from python to PowerShell works pretty well:

function sort-dir {
    param($dir)
    $toarray = {
        @($_.BaseName -split '(\d+)' | ?{$_} |
        % { if ([int]::TryParse($_,[ref]$null)) { [int]$_ } else { $_ } })
    }
    gci $dir | sort -Property $toarray
}

#try it
mkdir $env:TEMP\mytestsodir
1..10 + 100..105 | % { '' | Set-Content $env:TEMP\mytestsodir\$_.txt }
sort-dir $env:TEMP\mytestsodir
Remove-Item $env:TEMP\mytestsodir -Recurse

You can do it even better when you use Proxy function approach. You add -natur parameter to Sort-Object and you have pretty beautiful solution.

Update: First I was quite surprised that PowerShell handles comparing arrays in this way. After I tried to create test files ("a0", "a100", "a2") + 1..10 + 100..105 | % { '' | Set-Content $env:TEMP\mytestsodir\$_.txt }, it turned out that it doesn't work. So, I think there is no elegant solution like, because PowerShell is static under the covers, whereas python is dynamic.

I prefer @Larry Song's answer because it sorts exactly the way Windows Explorer does. I tried to simplify it a little to make it less intrusive.

Add-Type -TypeDefinition @"
using System.Runtime.InteropServices;
public static class NaturalSort
{
    [DllImport("Shlwapi.dll", CharSet = CharSet.Unicode)]
    private static extern int StrCmpLogicalW(string psz1, string psz2);
    public static string[] Sort(string[] array)
    {
        System.Array.Sort(array, (psz1, psz2) => StrCmpLogicalW(psz1, psz2));
        return array;
    }
}
"@

Then you can use it like:

$array = ('1.jpg', '10.jpg', '2.jpg')
[NaturalSort]::Sort($array)

which outputs:

1.jpg
2.jpg
10.jpg