powershell - How to strip illegal characters before trying to save filenames?

Question

I was able to find how to use the GetInvalidFileNameChars() method in a PowerShell script. However, it seems to also filter out whitespace (which is what I DON'T want).

EDIT: Maybe I'm not asking this clearly enough. I want the below function to INCLUDE the spaces that already existing in filenames. Currently, the script filters out spaces.

Function Remove-InvalidFileNameChars {

param([Parameter(Mandatory=$true,
    Position=0,
    ValueFromPipeline=$true,
    ValueFromPipelineByPropertyName=$true)]
    [String]$Name
)

return [RegEx]::Replace($Name, "[{0}]" -f ([RegEx]::Escape([String][System.IO.Path]::GetInvalidFileNameChars())), '')}

Answer 1

Casting the character array to System.String actually seems to join the array elements with spaces, meaning that

[string][System.IO.Path]::GetInvalidFileNameChars()

does the same as

[System.IO.Path]::GetInvalidFileNameChars() -join ' '

when you actually want

[System.IO.Path]::GetInvalidFileNameChars() -join ''

As @mjolinor mentioned (+1), this is caused by the output field separator ($OFS).

Evidence:

PS C:> [RegEx]::Escape([string][IO.Path]::GetInvalidFileNameChars())
"  |   ? ? ? ? ? ? \  
 ♂ f 
 ? ? ? ? ? ? ? § ? ? ↑ ↓ → ← ∟ ? ▲ ▼ : * ? \ /
PS C:> [RegEx]::Escape(([IO.Path]::GetInvalidFileNameChars() -join ' '))
"  |   ? ? ? ? ? ? \  
 ♂ f 
 ? ? ? ? ? ? ? § ? ? ↑ ↓ → ← ∟ ? ▲ ▼ : * ? \ /
PS C:> [RegEx]::Escape(([IO.Path]::GetInvalidFileNameChars() -join ''))
"| ????
♂f
???????§??↑↓→←∟?▲▼:*?\/
PS C:> $OFS=''
PS C:> [RegEx]::Escape([string][IO.Path]::GetInvalidFileNameChars())
"| ????
♂f
???????§??↑↓→←∟?▲▼:*?\/

Change your function to something like this:

Function Remove-InvalidFileNameChars {
  param(
    [Parameter(Mandatory=$true,
      Position=0,
      ValueFromPipeline=$true,
      ValueFromPipelineByPropertyName=$true)]
    [String]$Name
  )

  $invalidChars = [IO.Path]::GetInvalidFileNameChars() -join ''
  $re = "[{0}]" -f [RegEx]::Escape($invalidChars)
  return ($Name -replace $re)
}

and it should do what you want.