Why is my array being read as null? What am I missing? - arrays

Question

I am working on PowerShell script that will check server services. I keep getting a "Cannot index into a null array."
The error references the second if statement "if ($select_string_result.Line[$select_string_result.Line.Length-1] -eq '1')"
The object type of "$select_string_result" is displayed as Array and the txt file has data but the script will not process through it.
The "Line" property of the array records as null and the "Length" is recorded as 0.
$filepathserver = 'Path'
$filepathlocal = 'Path'
function Get-Timestamp
{
return Get-Date -Format "MM/dd/yyyy hh:mm:ss tt"
}
function refresh-data
{
# Pulls Services and Services Status
$orionData = Get-SwisData $swis "SELECT ComponentID, StatusDescription FROM Orion.APM.Component"
# Sends output to a txt file
$orionData | Out-File "$filepathlocal\All_App_Services.txt"
}
function check-status($select_string_result)
{
if ($select_string_result.Line -isnot [system.array])
{
if ($select_string_result.Line[$select_string_result.Line.Length-1] -eq '1')
{
return 100
}
else
{
return 0
}
}
else
{
$sum = 0.0
$add = 100.0/$select_string_result.Length
foreach ($match in $select_string_result)
{
if ($match.Line[$match.Line.Length-1] -eq '1')
{
$sum += $add
}
}
if ($sum -lt 100) {$sum = 0} # this line collapses the values in to either 0 or 100
$sum = [int][Math]::Ceiling($sum)
return $sum
}
}
function main
{
refresh-data
# Filters for Application specific Services
$f = #("94944 ", "94945 ", "94951 ", "94946 ", "94942 ", "94948 ", "94949 ", "94950 ", "94943 ", "94947 ", "94952 ", "94953 ")
$AppServices = Get-Content "Path" | Select-String $f
$AppServices | Set-Content "Path"
#Removes leading spaces from array
(Get-Content "$filepathlocal\File.txt") -replace "Up","1" | % {$_.trim()} | Out-File "$filepathlocal\File.txt"
$AppServices = Get-Content "$filepathlocal\File.txt"
$AppServices.GetType()
# Writes status of each group to .txt file
$logfile= "$filepathserver\ServicesStatus.txt"
$t = Get-Timestamp
$v = check-status $AppServices
$s = "$t|Application-Services|$v"
$s | Out-File $logfile -Append -Encoding "UTF8"
$s
}
main

Answer 1

$select_string_result.Line resolves to $null because the array of strings that you get from Get-Content does not have a Line property, so the if statement should look more like:
if($select_string_result[$select_string_result.Length - 1] -eq '1') { ... }
PowerShell also allows you to address the last index with just -1, allowing us to simplify the statement as:
if($select_string_result[-1] -eq '1') { ... }
That being said, rather than attempting to check whether the parameter passed to a function is an array or not, you'd want to declare the parameter an array in the first place and then use a foreach loop over it:
function check-status([string[]]$select_string_result)
{
$sum = 0.0
$add = 100.0/$select_string_result.Length
foreach ($match in $select_string_result)
{
if ($match[-1] -eq '1')
{
$sum += $add
}
}
if ($sum -lt 100) {$sum = 0} # this line collapses the values in to either 0 or 100
$sum = [int][Math]::Ceiling($sum)
return $sum
}
much nice, way less code.
Now, instead of attempting to index into the string, I'd suggest using the -like wildcard operator or the -match regex operator to check whether each string ends with 1:
if ($match -like '*1')
{
$sum += $add
}
Since $sum is always exactly 100, or otherwise gets reset to 0, the call to [Math]::Ceiling() is redundant and can be removed:
function check-status([string[]]$select_string_result)
{
$sum = 0.0
$add = 100.0/$select_string_result.Length
foreach ($match in $select_string_result)
{
if ($match -like '*1')
{
$sum += $add
}
}
if ($sum -lt 100) {$sum = 0} # this line collapses the values in to either 0 or 100
return $sum
}
If you look carefully at the function as implemented, you'll notice that the only case in which 100 is returned is when all strings in $select_string_result end in 1.
We can easily test for this by using the -like operator directly on our input array, it will act as a filter operator:
function check-status([string[]]$select_string_result)
{
if(#($select_string_result -like '*1').Count -eq $select_string_result.Count)
{
$sum = 100
}
else
{
$sum = 0
}
return $sum
}
Now, another way of asserting that all strings in the array end in 1, is to simply test whether no string does not end in 1:
function check-status([string[]]$select_string_result)
{
if(#($select_string_result -notlike '*1'))
{
$sum = 0
}
else
{
$sum = 100
}
return $sum
}
Now all we need to do is shine it up a bit, like change check to a more appropriate verb and we've got a much nicer, short or powershell-idiomatic function :-)
function Measure-StatusValue
{
param(
[ValidateNotNullOrEmpty()]
[string[]]$StatusStrings
)
if(#($StatusStrings -notlike '*1'))
{
return 0
}
return 100
}