Powershell challenge

Question

I've been challenged by a friend to do the following:

"Find the quickest and easiest way of sorting a directory listing by the LAST character of the filenames."

He's done it on Linux using the following:

ls | rev | sort | rev

I'd like to show him the powershell alternative, but I'm only just starting to learn powershell and I can't do it. So, I'm cheating and asking for your help.

Answer 1

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.

Answer 2

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

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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'.

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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.

Answer 3

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

Answer 4

Shay's variant is way shorter than the accepted answer by indexing into the string but even that can be improved. You can shorten it even more by excluding unnecessary spaces and using a shorter alias:

ls|sort{$_.Name[-1]}

Also you can use the (abbreviated) -Name argument to Get-ChildItem:

ls -n|sort{$_[-1]}

which will return strings directly.

If you really want to sort by the reverse string, then the following works (but is slow):

ls -n|sort{$_[3e3..0]}

You can make it faster if you have an upper bound on the file name's length.

Answer 5

Here's my entry:

ls | sort {"$_"[-1]}

and to get pathological:

ls|sort{"$_"[-1]}