Background

It is a lovefest for me to do any work in Powershell.

 

Variable Declaration

Having admitted that I am a 60s love child when it comes to Powershell,  I am not quite a fan of its laissez-faire when it comes to variable declarations.

 

Sample Code

Let us get a list of files on our home directory

<#
    Declare variables
#>
[string] $folder ="";
[string] $log = "";
[object] $fileList =$null;

<#
    Get home directory
#>
$folder=$HOME

<#
    Get list of files from our home directory
#>
$fileList = Get-ChildItem -Path $folder;


<#
    If file list is not null
#>
if ($fileList -ne $null )
{
   
   
    <#
        Display folder name
    #>
    $log = "Folder is {0}" -f $folder;
    
    Write-Host $log            
    
    <#
        Get list of files
    #>
    $fileList

}

 

 

 

Explanation

Variable Declaration

So we have declared three variables.

1. $folder as a string
2. $fileList as an object
3. $log as a string

 

No arguments with our definition of folder and log.

But, declaring $fileList as an object, seems a bit ‘catch all‘.

A man for all seasons so to speak.

 

What is the actual type of $fileList?

 

Outline

Please use GetType to get the actual type of the object.

Code

<#
    Declare variables
#>
[string] $folder ="";
[string] $log = "";

[object] $fileList =$null;

[object] $fileListType = "";

[type]   $fileListType = $null;

[string] $fileListTypeName = "";

[string] $fileListTypeBaseType ="";
 
[boolean] $displayMetadataOnly = $false; 

$displayMetadataOnly = $true;

<#
    Get home directory
#>
$folder=$HOME

<#
    Get list of files from our home directory
#>
$fileList = Get-ChildItem -Path $folder;


<#
    If file list is not null
#>
if ($fileList -ne $null )
{

    Write-Host "";
    
    Write-Host "";
    
    <#
        Display folder name
    #>
    $log = "Folder is {0}" -f $folder;
    
    if ($displayMetadataOnly -eq $false)
    {
        
        Write-Host $log; 
        
    }
 
    <#
        Get type of fileList
    #>
    $fileListType = $fileList.GetType();
    
    $fileListType;
    
    $fileListTypeName = $fileListType.Name;
           
    $fileListTypeBaseType = $fileListType.BaseType;
    
   
    <#
        Display fileList type
    #>
    $log = "The name of the type of fileList is {0}" -f $fileListTypeName;
    
    Write-Host $log;    


    <#
        Display fileList base type
    #>
    $log = "The base type of fileList is {0}" -f $fileListTypeBaseType;
    
    Write-Host $log;
    
    $log = "The base type of fileList is {0}" -f $fileListType.BaseType;
    
    Write-Host $log;    
    
    <#
        Get list of files
    #>
    if ($displayMetadataOnly -eq $false)
    {

        $fileList
    
    }

}

 

Output

Image

Explanation

1. GetType()
   • Get Object’s type
2. GetType().Name
   • The name of the returned type is object[]
3. GetType().BaseType
   • The base type of the returned type is System.Array

 

 

Use the actual type of $fileList?

 

Outline

Please use the actual type of each variable.

Code

<#
    Declare variables
#>
[string] $folder ="";
[string] $log = "";

<#
    Changed $fileList
        from:- [object]
        to:-   [object[]]
#>
#[object] $fileList =$null;
[object[]] $fileList =$null;

<#
    Get home directory
#>
$folder=$HOME

<#
    Get list of files from our home directory
#>
$fileList = Get-ChildItem -Path $folder;


<#
    If file list is not null
#>
if ($fileList -ne $null )
{

    Write-Host "";
    
    Write-Host "";
    
    <#
        Display folder name
    #>
    $log = "Folder is {0}" -f $folder;
    
    Write-Host $log; 
  
    $fileList
    
  
}

 

Source Code Control

GitHub

Repository

https://github.com/DanielAdeniji/fileSystem.fileList/tree/main/powershell

Link

 

Summary

Variable declaration is not required in PowerShell.

Yet, declaring your variables will:-

1. Further Readability
2. Deepen your understanding of the API Set
3. Hopefully, lessen the likelihood of errors
4. Help your programming chops in this language and other more stringent languages