Error in foreach that it cannot index into a null array

Question

Following an answer here. I am doing the following:

param(
    # Required. Download source location (website).
     [Parameter(Mandatory=$True)]
     [URI] $URL
)
process
{
     $wc = New-Object System.Net.WebClient;
     $fileItems = $wc.downloadstring($URL) -split "<a\s+" | %{ [void]($_ -match "^HREF=[`'`"]  ([^`'`">\s]*)"); $matches[1] };
     return $fileItems;
}

I am getting the following error:

ForEach-Object : Cannot index into a null array.
At J:\LMIData\PowerShell\HTTP_based_downloader.ps1:9 char:61
+     $fileItems = $wc.downloadstring($URL) -split "<a\s+" | % <<<< { [void]($_ -match "^HREF=[`'`"]([^`'`">\s]*)"); $matches[1]; };
    + CategoryInfo          : InvalidOperation: (1:Int32) [ForEach-Object], RuntimeException
    + FullyQualifiedErrorId : NullArray,Microsoft.PowerShell.Commands.ForEachObjectCommand

The "char:61" location is right after the %.

Now, what is interesting is that this code worked previously. Is this possibly an issue in the -match regex? I have not declared the $matches array - could that be it?

I am at a loss here as I am still new to powershell. I am aware that I can get the list of links in powershell v3+ using Invoke-WebRequest but that is not an option as the system this is running on is locked at v2 for the time being.

mjolinor · Accepted Answer · 2014-01-24 19:33:00Z

2

Looks more like your download might not be what you expected. Try adding some debug.

param(
    # Required. Download source location (website).
     [Parameter(Mandatory=$True)]
     [URI] $URL
  )
  process
  {
     $wc = New-Object System.Net.WebClient;
     $Download = $wc.downloadstring($URL)
     Write-Debug "Download is $Download"
     $fileItems = $Download -split "<a\s+" | %{ [void]($_ -match "^HREF=[`'`"]  ([^`'`">\s]*)"); $matches[1] };
     return $fileItems;
  }

and set your $DebugPreference to 'Continue' amd see what your d/l payload looks like.

answered Jan 24, 2014 at 19:33

mjolinor

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8 Comments

wergeld Over a year ago

As I said. I am a newbie to PS. What is $DebugPreference

wergeld Over a year ago

If I just return $Download or if I return just $Download -split "<a\s+" I have the expected output.

mjolinor Over a year ago

What happens if you return the split and run it through that match?

wergeld Over a year ago

Same error. It has just moved to the line where I try and do the match. If I initialize the $match like '$match = @()` I no longer get the error but I do not get an array either.

mjolinor Over a year ago

Then your regex isn't capturing anything.

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