How do I create an alias to Format-Table in Powershell?

Question

Suppose I have a Powershell Format-Table string, something like:

ls | Format-Table Name, @{expression={$_.Length / 1024}; label='KB'}

I'm happy with the output I get from this, but I don't want to type it every time I use it. I'd like to be able to call it with a simple one-word command, something like:

ls | Format-KiloBytes

I gather I should be defining a function for this, since an alias can't specify the parameters. However, if I define something like:

function kilobytes {format-table Name, @{expression={$_.Length / 1024}; label='KB'}}

then it doesn't have any effect:

PS> ls | format-table Name, @{expression={$_.Length / 1024}; label='KB'}
   ... Produces the formatted output

PS> ls | kilobytes
   ... Produces output with unchanged formatting, the same as 'ls'

Edit: It appears I was confused. When experimenting, I'd already created an alias kilobytes that was aliased to Format-Table . I'd forgotten this, but this meant that creating a function kilobytes succeeded without any warning, but subsequently calling kilobytes wasn't calling the newly-created function but the existing alias.

Answer 1

First you can try :

function kilobytes {$input | format-table Name, @{expression={$_.Length / 1024}; label='KB'}}

You can find the explanation of $input in about_Functions . When you use a function in a pipeline, the objects piped to the function are assigned to the $input automatic variable.

Answer 2

Here's a working Filter version:

filter kilobytes {$_ | select Name,@{expression={$_.Length / 1024}; label='KB'}}

Or:

filter kilobytes {[PSCustomObject]@{Name=$_.name;KB=$_.length/1024}}

Answer 3

A proxy function provides a good way to bind one or more parameters while still supporting the original command in a natural way. A search on Bing for "powershell proxy function" will give lots of good details.

Below is a proxy function that does exactly what you want. You can see how you still have the Format-Table parameters like -AutoSize, but no -Property parameter as that has been hard coded.

A smarter version of this proxy might actually support adding additional properties to the hard coded ones.

function Format-Kilobytes
{
    [CmdletBinding(HelpUri='http://go.microsoft.com/fwlink/?LinkID=113303')]
    param(
        [switch]${AutoSize},
        [switch]${HideTableHeaders},
        [switch]${Wrap},
        [System.Object]${GroupBy},
        [string]${View},
        [switch]${ShowError},
        [switch]${DisplayError},
        [switch]${Force},
        [ValidateSet('CoreOnly','EnumOnly','Both')]
        [string]${Expand},
        [Parameter(ValueFromPipeline=$true)]
        [psobject]${InputObject})

begin
{
    try {
        $wrappedCmd = $ExecutionContext.InvokeCommand.GetCommand('Format-Table',
            [System.Management.Automation.CommandTypes]::Cmdlet)
        $properties = "Name",@{expression={$_.Length / 1024}; label='KB'}
        $scriptCmd = {& $wrappedCmd @PSBoundParameters -Property $properties }
        $steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin)
        $steppablePipeline.Begin($PSCmdlet)
    } catch {
        throw
    }
}
process { try { $steppablePipeline.Process($_) } catch { throw } }
end { try { $steppablePipeline.End() } catch { throw } }
<#
.ForwardHelpTargetName Format-Table
.ForwardHelpCategory Cmdlet
#>
}