Powershell challenge

Solution 1:

You can try this:

dir| sort {$_.name[-1]}

Solution 2:

Unfortunately Powershell does not have a nice easy reverse method, so instead you have to get the last letter of the string and sort by that. This is one way i've done it:

dir| sort {$_.name.Substring($_.name.length-1)}

As has been pointed out, this will sort strictly by the last letter only, whereas I the Linux version will sort by the last and then subsequent letters, so there may be a better way of doing this, or you may have to introduce some looping if you want it that way.

Solution 3:

dir | sort -Property @{Expression ={$n = $_.Name.ToCharArray(); [Array]::Reverse($n);[String]::Join("",$n)}}

Not as short as the unix version, mostly because there isn't a String.Reverse() function in the .NET Framework. Basically this works by telling sort 'sort by computing this expression on the input arguments'.

Now, if any unix shell does better than

dir | sort -Property Length -Descending

to print all the files with the largest one first, I'd be interested to see it.

Solution 4:

I'm sure someone can do this better, but here is one way that is fully compatible with lynix. It has the benefit of leaving you with a reusable rev string function for your toolbox, i.e. it sorts the entire string and not just the last character:

function rev ($s) {return -join ($s[$s.Length..0])}

dir | foreach{rev($_.name)} | sort | foreach{rev($_)}

I think the foreach's here nicely demonstrate how PowerShell pipes are arrays and not simply strings like in *nix.

It took me a little while to realize that I had to use only $_ and not $_.name inside the 2nd foreach. So I've learned something about variations in the array content from one pipe to the next.

*Credit for the guts of my rev function goes to http://rosettacode.org/wiki/Reverse_a_string#PowerShell

Works like lynix:

  • dir | sort -Property @{Expression ={$n = $_.Name.ToCharArray(); [Array]::Reverse($n);[String]::Join("",$n)}}

Sort of works like lynix, but very, very slow:

  • ls -n|sort{$_[3e3..0]}

Do not work like lynix, i.e. fail to sort all characters of the file names; (only sorts the very last character of the string):

  • dir| sort {$.name.Substring($.name.length-1)}
  • dir| sort {$_.name[-1]}
  • ls|sort{$_.Name[-1]}
  • ls|sort{"$_"[-1]}
  • ls -n|sort{$_[-1]}

Tags:

Powershell

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