Options to use different param - powershell

Question

I'm looking for a way to to have a choice of a list or a single computername in a foreach loop.
If the user enters in a single computername I want the script to execute for that one computername
but if that user wants to use a path to a list of computers how could I replace $computername with the path that user wants?
function Get-OSInfo {
[CmdletBinding()]
param (
#[Parameter(ValueFromPipeline=$True,
# ValueFromPipelineByPropertyName=$True)]
[string]$computername,
[string]$errorlog = 'c:\errors.txt',
[switch]$logerrors
)
PROCESS {
foreach ($computer in $computername) {
Try {
$os = Get-WmiObject -EA Stop –Class Win32_OperatingSystem –ComputerName $computer
$cs = Get-WmiObject -EA Stop –Class Win32_ComputerSystem –ComputerName $computer
$bios = Get-WmiObject -EA Stop –Class Win32_BIOS –ComputerName $computer
$cpu = Get-WmiObject -EA Stop -class Win32_processor -ComputerName $computer
$props = #{'ComputerName'=$computer;
'OSVersion'=$os.version;
'SPVersion'=$os.servicepackmajorversion;
'OSBuild'=$os.buildnumber;
'OSArchitecture'=$os.osarchitecture;
'Manufacturer'=$cs.manufacturer;
'Model'=$cs.model;
'BIOSSerial'=$bios.serialnumber
'CPU Count'=$CPU.Count
'Memory'= [Math]::round(($cs.TotalPhysicalMemory/1gb),2)
'CPU Speed'= $CPU.MaxClockSpeed[0]}
$obj = New-Object -TypeName PSOBject -Property $props
$obj.PSObject.TypeNames.Insert(0,'Get-OS.OSInfo')
#Write-Output $obj
$obj | Export-Csv c:\test4.csv -Append
} Catch {
if ($logerrors) {
$computer | Out-File $errorlog -append
}
Write-Warning "$computer failed"
}
}
}
}

Answer 1

Change the type of the $ComputerName parameter to a string array instead of just a single string:
param(
[string[]]$ComputerName,
[string]$errorlog = 'c:\errors.txt',
[switch]$logerrors
)
Notice the [] after the type name, this denotes an array of strings, rather than a single string.
Now you can do:
PS C:\> $computers = Get-Content C:\computers.txt
PS C:\> Get-OSInfo -ComputerName $computers
If you'd like to be able to specify a path to a file containing the target computers as the argument to the function, you can use multiple parameter sets:
[CmdletBinding(DefaultParameterSetName='ByName')]
param(
[Parameter(ParameterSetName='ByName',ValueFromPipeline)]
[string[]]$ComputerName,
[Parameter(ParameterSetName='ByFile')]
[string]$InputFile
)
begin {
if($PSCmdlet.ParameterSetName -eq 'ByFile'){
try{
$ComputerName = Get-Content -LiteralPath $InputFile
}
catch{
throw
return
}
}
}
process {
foreach($Computer in $ComputerName){
# Work with $Computer here...
}
}