Pull specific data from text files in PowerShell with search parameters

As a general solution, you might consider this (custom) ConvertFrom-SourceTable cmdlet:

The latest version (0.5.1, just uploaded) supports suppressing certain columns by supplying an empty column name:

Install-Script -Name ConvertFrom-SourceTable

Get-Content $Files | Select-String -Pattern '^\w\w:\w\w:\w\w:\w\w:\w\w:\w\w' |
  ConvertFrom-SourceTable -Header 'bss', 'ess', '', '', '', '', '', '', 'ap name'

Explanation:

• The Select-String -Pattern '^\w\w:\w\w:\w\w:\w\w:\w\w:\w\w' command, selects all the lines (data rows) that start with a mac address
• Each data row is passed to the ConvertFrom-SourceTable cmdlet which determines the columns based on their fixed size (and spaces in between).
• The header names (-Header 'bss', 'ess', '', '', '', '', '', '', 'ap name') are applied to each of the corresponding column with the same index

Note that the above command will not work if the concerned tables have different column widths. In that case you might convert each table separately:

$Files | ForEach-Object { 
    Get-Content $_ | Select-String -Pattern '^\w\w:\w\w:\w\w:\w\w:\w\w:\w\w' |
      ConvertFrom-SourceTable -Header 'bss', 'ess', '', '', '', '', '', '', 'ap name'
}

For either command the order of the (captured) columns needs to same (e.g. the 'ap name' column is presumed to be the 9th column).

Try following

$filename = "c:\temp\test.txt"

$lines = Get-Content -Path $filename

$patternAP = 'Target:\s+(?<ap>[^\s]+)'
$patternBss = '^(?<bss>[a-z]{2}:[a-z]{2}:[a-z]{2}:[a-z]{2}:[a-z]{2}:[a-z0-9]{2})\s+(?<ess>[^\s]+)\s+(?<port>[^\s]+)\s+(?<ip>[^\s]+)\s+(?<band>[^\s]+)\s+(?<ch>[^\s]+)\s+(?<type>[^\s]+)\s+(?<cur>[^\s]+)\s+(?<apname>[^\s]+)\s+(?<in>[^\s]+)\s+(?<tot>[^\s]+)\s+(?<flags>[^\s]+)'
$table = [System.Collections.Generic.List[pscustomobject]]::new()
foreach($line in $lines)
{
   if($line -match $patternAP)
   {
      $line -match $patternAP | Out-Null
      $ap = $matches.ap
   } `
   else
   {

      if($line -match $patternBss)
      {
         $line -match $patternBss | Out-Null
         if($matches.ess -eq 'guest')
         {
             $newRow = [pscustomobject]@{
                ap = $ap
                bss = $matches.bss
                ess = $matches.ess
                port = $matches.port
                ip = $matches.ip
                'band/ht-mode/bandwidth' = $matches.band
                'ch/EIRP/max-EIRP' = $matches.ch
                type = $matches.type
                'curl-cl' = $matches.cur
                'ap name' = $matches.apname
                'in-t(s)' = $matches.in
                'tot-t' = $matches.tot
                'flags' = $matches.flags
             }
             $table.Add($newRow)  | Out-Null
         }
      }
   }
}

$table | format-list

Results

ap                     : AP01
bss                    : ab:cd:ef:gh:if:jk
ess                    : guest
port                   : ?/?
ip                     : A.b.c.d
band/ht-mode/bandwidth : 2.4GHz/HT/20MHz
ch/EIRP/max-EIRP       : 1/24.0/25.5
type                   : ap
curl-cl                : 0
ap name                : AP01
in-t(s)                : 0
tot-t                  : 22h:11m:43s
flags                  : -

ap                     : AP01
bss                    : ab:cd:ef:gh:if:jk
ess                    : guest
port                   : ?/?
ip                     : A.b.c.d
band/ht-mode/bandwidth : 5GHz/VHT/40MHz
ch/EIRP/max-EIRP       : 100+/18.0/30.0
type                   : ap
curl-cl                : 0
ap name                : AP01
in-t(s)                : 0
tot-t                  : 22h:11m:44s
flags                  : -

ap                     : AP02
bss                    : ab:cd:ef:gh:if:jm
ess                    : guest
port                   : ?/?
ip                     : A.b.c.d
band/ht-mode/bandwidth : 2.4GHz/HT/20MHz
ch/EIRP/max-EIRP       : 11/24.0/25.5
type                   : ap
curl-cl                : 0
ap name                : AP02
in-t(s)                : 0
tot-t                  : 22h:11m:43s
flags                  : -

ap                     : AP02
bss                    : ab:cd:ef:gh:if:jq
ess                    : guest
port                   : ?/?
ip                     : A.b.c.d
band/ht-mode/bandwidth : 5GHz/VHT/40MHz
ch/EIRP/max-EIRP       : 108+/18.0/30.0
type                   : ap
curl-cl                : 0
ap name                : AP02
in-t(s)                : 0
tot-t                  : 22h:11m:43s
flags                  : -

After reviewing code I found a simpler method. Original code was geting AP from line between the asterisks. New code is getting AP from column 'ap -name'

$filename = "c:\temp\test.txt"

$lines = Get-Content -Path $filename

$patternBss = '^(?<bss>[a-z]{2}:[a-z]{2}:[a-z]{2}:[a-z]{2}:[a-z]{2}:[a-z0-9]{2})\s+(?<ess>[^\s]+)\s+(?<port>[^\s]+)\s+(?<ip>[^\s]+)\s+(?<band>[^\s]+)\s+(?<ch>[^\s]+)\s+(?<type>[^\s]+)\s+(?<cur>[^\s]+)\s+(?<apname>[^\s]+)\s+(?<in>[^\s]+)\s+(?<tot>[^\s]+)\s+(?<flags>[^\s]+)'
$table = [System.Collections.Generic.List[pscustomobject]]::new()
foreach($line in $lines)
{
   if($line -match $patternBss)
   {
      $line -match $patternBss | Out-Null
      if($matches.ess -eq 'guest')
      {
          $newRow = [pscustomobject]@{
             bss = $matches.bss
             ess = $matches.ess
             port = $matches.port
             ip = $matches.ip
             'band/ht-mode/bandwidth' = $matches.band
             'ch/EIRP/max-EIRP' = $matches.ch
             type = $matches.type
             'curl-cl' = $matches.cur
             'ap name' = $matches.apname
             'in-t(s)' = $matches.in
             'tot-t' = $matches.tot
             'flags' = $matches.flags
         }
         $table.Add($newRow)  | Out-Null
      }
   }
}

$table | format-list

Assuming all columns in your files are in the same order and all fields are separated by at least 2 spaces like you show in your post, then a quick and dirty way of parsing out the values you need could be like below:

$sourcePath = 'D:\Test'
$outputFile = 'D:\Test\result.csv'

$result = Get-ChildItem -Path $sourcePath -Filter '*.txt' -File | ForEach-Object {
    switch -Regex -File $_.FullName {
        '^..:..:..:..:..:..' {
            $data = $_ -split '\s{2,}'
            # You could process only items where column 'ess' ($data[1]) 
            # is either 'trustedwifi' or 'guest' at this point:
            if ($data[1] -match 't?rustedwifi|guest') {
                # output an object with the columns needed
                [PsCustomObject]@{
                    appname = $data[8]
                    ess     = $data[1]
                    bss     = $data[0]
                }
            }
        }
    }
}

# save the result
$result | Export-Csv -Path $outputFile -NoTypeInformation

# if you didn't use the filtering for 'trustedwifi' or 'guest' in the above, you can do that here:
$result | Where-Object { $_.ess -match 't?rustedwifi|guest' } | Export-Csv -Path $outputFile -NoTypeInformation

P.S. In your example, there is a t missing in one of the rows for trustedwifi, so that is why the regex now uses t?rustedwifi. If that is just a typo in your post and does not occur in the real files, just remove the questionmark in the regex.