Use Regex / Powershell to rename files

Try this one:

Get-ChildItem directory `        | Rename-Item -NewName { $_.Name -replace '^filename_+','' -replace '_+',' ' }

Note that I just pipe the objects to Rename-Item, it is not really needed to do it via Foreach-Object (alias is %).

Update

I haven't anything documented about the 'magic' with scriptblocks. If I remember correctly, it can be used if the property is ValueFromPipelineByPropertyName=$true:

function x{    param(        [Parameter(ValueFromPipeline=$true)]$o,        [Parameter(ValueFromPipelineByPropertyName=$true)][string]$prefix)    process {        write-host $prefix $o    }}gci d:\ | select -fir 10 | x -prefix { $_.LastWriteTime }

This should work:

ls | %{ ren $_ $(($_.name -replace '^filename_+','') -replace '_+',' ') }

Expanding the aliases and naming all argument, for a more verbose but arguably more understandable version, the following is equivalent

Get-ChildItem -Path . | ForEach-Object { Rename-Item -Path $_ -NewName $(($_.Name -replace '^filename_+','') -replace '_+',' ') }

Try this out:

$filename = $filename -creplace '_+\.', '.'$filename = $filename -creplace '_+', ' '