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published: April 24, 2023 author: Tinu tags: PowerShell categories: PowerShell-Basic
Table of Contents
Define the Function
A function for some file-handling examples. First we see a parameter block with ValidateScript to ensure that a file has been specified. The type of this parameter must be a file. The second paramter is only a switch for the output.
function Invoke-MwaFileReader {
[CmdletBinding()]
param(
# Parameter block with ValidateScript and a custom message if the file not exists
[Parameter(
HelpMessage = 'Specify a valide fullname of a file to read.',
Mandatory = $true,
ValueFromPipeline = $true,
ValueFromPipelineByPropertyName = $true,
Position = 0
)]
[ValidateScript({ if(Test-Path -Path $($_) ){$true}else{Throw "File '$($_)' not found"} })]
[System.IO.FileInfo]$file,
# Only a switch for output or not
[Parameter(Mandatory = $false)]
[Switch]$Out
)
begin{
$StartTime = Get-Date
$function = $($MyInvocation.MyCommand.Name)
Write-Verbose $('[', (Get-Date -f 'yyyy-MM-dd HH:mm:ss.fff'), ']', '[ Begin ]', $function -Join ' ')
$ret = $null
}
process{
Write-Verbose $('[', (Get-Date -f 'yyyy-MM-dd HH:mm:ss.fff'), ']', '[ Process ]', $function -Join ' ')
try{
Write-Verbose "$($file)"
switch -RegEx ($file.Extension -replace '\.'){
'csv' {
# if the file-extension is a csv, then you can use Import-Csv to read it as an object
Write-Verbose "Its a $($_)"
$ret = Import-Csv -Delimiter ';' -Path $file.FullName
}
'json' {
# if the file-extension is a json, then you can user Get-Content and | ConvertFrom-Json to read and format ist as an object
Write-Verbose "Its a $($_)"
$ret = Get-Content -Path $file.FullName | ConvertFrom-Json
}
default {
# the default ist not defined and use Get-Content to read it
Write-Verbose "Its a $($_)"
$ret = Get-Content -Path $file.FullName
}
}
}catch{
Write-Warning $('ScriptName:', $($_.InvocationInfo.ScriptName), 'LineNumber:', $($_.InvocationInfo.ScriptLineNumber), 'Message:', $($_.Exception.Message) -Join ' ')
$Error.Clear()
}
}
end{
Write-Verbose $('[', (Get-Date -f 'yyyy-MM-dd HH:mm:ss.fff'), ']', '[ End ]', $function -Join ' ')
$TimeSpan = New-TimeSpan -Start $StartTime -End (Get-Date)
$Formatted = $TimeSpan | ForEach-Object {
'{1:0}h {2:0}m {3:0}s {4:000}ms' -f $_.Days, $_.Hours, $_.Minutes, $_.Seconds, $_.Milliseconds
}
Write-Verbose $('Finished in:', $Formatted -Join ' ')
if($Out){ return $ret }
}
}
Call the function
We call the function with the named parameter file:
Invoke-MwaFileReader -file "D:\github.com\PSXiDiag\data\inventory.csv" -Verbose
The file is a CSV and is importet as an objet with Import-Csv.
VERBOSE: [ 2023-04-24 18:31:23.086 ] [ Begin ] Invoke-MwaFileReader
VERBOSE: [ 2023-04-24 18:31:23.087 ] [ Process ] Invoke-MwaFileReader
VERBOSE: D:\github.com\PSXiDiag\data\inventory.csv
VERBOSE: Its a csv
VERBOSE: [ 2023-04-24 18:31:23.087 ] [ End ] Invoke-MwaFileReader
VERBOSE: Finished in: 0h 0m 0s 001ms
HostName : ESXi7912.my.company.ch
Version : 6.7
Manufacturer : HPE
Model : ProLiant DL380 Gen10
vCenterServer : vCSA021.my.company.ch
Cluster : Oracle
PhysicalLocation : Ost
ConnectionState : Connected
Next we call the function with the parameter at position 0 for file:
Invoke-MwaFileReader "D:\github.com\PSXiDiag\data\Inventory.json" -Verbose
The file is a JSON and is importet with Get-Content and formatet as object with ConvertFrom-Json.
VERBOSE: [ 2023-04-24 18:31:28.611 ] [ Begin ] Invoke-MwaFileReader
VERBOSE: [ 2023-04-24 18:31:28.611 ] [ Process ] Invoke-MwaFileReader
VERBOSE: D:\github.com\PSXiDiag\data\Inventory.json
VERBOSE: Its a json
VERBOSE: [ 2023-04-24 18:31:28.613 ] [ End ] Invoke-MwaFileReader
VERBOSE: Finished in: 0h 0m 0s 002ms
HostName : ESXi7912.my.company.ch
Version : 6.7
Manufacturer : HPE
Model : ProLiant DL380 Gen10
vCenterServer : vCSA021.my.company.ch
Cluster : Oracle
PhysicalLocation : Ost
ConnectionState : Connected
Next we use the function with pipe the parameter for file:
"D:\temp\words.txt" | Invoke-MwaFileReader -Verbose
The file is a Textfile and importet with Get-Content.
VERBOSE: [ 2023-04-24 18:31:32.502 ] [ Begin ] Invoke-MwaFileReader
VERBOSE: [ 2023-04-24 18:31:32.502 ] [ Process ] Invoke-MwaFileReader
VERBOSE: D:\temp\words.txt
VERBOSE: Its a txt
VERBOSE: [ 2023-04-24 18:31:32.510 ] [ End ] Invoke-MwaFileReader
VERBOSE: Finished in: 0h 0m 0s 008ms
Show-NetFirewallRule
Show-NetIPsecRule
Show-StorageHistory
Show-Tree
Show-VirtualDisk
Start-AppBackgroundTask
Start-AppvVirtualProcess
Start-AutologgerConfig
Next we call the function with a wrong file-path:
Invoke-MwaFileReader "D:\NotExists.txt" -Verbose
The file does not exists and the ValidateScript-Block returned the custom-defined message.
Invoke-MwaFileReader: Cannot validate argument on parameter 'file'. File 'D:\NotExists.txt' not found
Next we call the function with an empty file-path:
Invoke-MwaFileReader -file
We forgot the file-path and the type-definition in the paramter returned the default message.
Invoke-MwaFileReader: Missing an argument for parameter 'file'. Specify a parameter of type 'System.IO.FileInfo' and try again.
Next we call the function with no parameter and type at the prompt for file ‘!?’ to get the HelpMessage:
Invoke-MwaFileReader # Type !? at the prompt for file
cmdlet Invoke-MwaFileReader at command pipeline position 1
Supply values for the following parameters:
(Type !? for Help.)
file: !?
Specify a valide fullname of a file to read.
file:
See also
ValidateScript Attribute Declaration on Microsoft.