Advanced Windows PowerShell Scripting Video Training

Advanced Windows PowerShell Scripting Video Training
Advanced Windows PowerShell Scripting Video Training

Wednesday, October 5, 2016

Creating an Error Log: To Append or not to Append

This is day 3 of how to create an error log.

You may be faced with a situation when you want to clear the error log before running your code.  We are now going to start building the code for our scenario from Monday. 

Function Test-ADUsers
{
    [CmdletBinding()]
    Param (
        [String[]]
        $Names

    )

    ForEach ($Name in $Names)
    {
        Try {Get-ADUser -Identity $Name -ErrorAction Stop}
        Catch {}
    }

} # END: Function Test-ADUsers

Test-ADUsers -Names "Administrator", "Bad" , "Administrator"

I left the test line at the end of the code so you can copy this into the ISE or SAPIEN PowerShell Studio and just execute the code.  Notice that we are not doing anything in our error handling as of yet.  Our next step is to add in the Test-ErrorLog code from yesterday.

Function Test-ADUsers
{
    [CmdletBinding()]
    Param (
        [parameter(Mandatory=$true)]
        [String[]]
        $Names

# Begin Support Functions
    )
    Function Test-ErrorLog
    {
    [CmdletBinding()]
    Param (
        [parameter(Mandatory=$true)]
        [String]
        $Path,

        [parameter(Mandatory=$true)]
        [String]
        $Name
        )

        # Test the path.
        If (!(Test-Path -Path $Path))
        {
            Write-Verbose "Creating the directory $Path"
            New-Item -Path $Path -ItemType Directory
        }

        # Test the file
        If (!(Test-Path -Path "$Path\$Name"))
        {
            Write-Verbose "Creating the file $Name"
            New-Item -Path "$Path\$Name" -ItemType File
        }

    } # END: Function Test-ErrorLog

# End Support Functions

    # Verify that the error log is present.
    Test-ErrorLog -Path c:\ps -Name Errorlog.csv

    ForEach ($Name in $Names)
    {
        Try {Get-ADUser -Identity $Name -ErrorAction Stop}
        Catch {}
    }

} # END: Function Test-ADUsers

Test-ADUsers -Names "Administrator", "Bad" , "Administrator"

I removed the help file for Test-ErrorLog to help keep this post reasonably short.  Next we add a parameter to clear the error log if we want to.  We will call it –NoAppend.
Function Test-ADUsers
{
    [CmdletBinding()]
    Param (
        [parameter(Mandatory=$true)]
        [String[]]
        $Names,

        [Switch]
        $NoAppend

# Begin Support Functions
    )
    Function Test-ErrorLog
    {
    [CmdletBinding()]
    Param (
        [parameter(Mandatory=$true)]
        [String]
        $Path,

        [parameter(Mandatory=$true)]
        [String]
        $Name
        )

        # Test the path.
        If (!(Test-Path -Path $Path))
        {
            Write-Verbose "Creating the directory $Path"
            New-Item -Path $Path -ItemType Directory
        }

        # Test the file
        If (!(Test-Path -Path "$Path\$Name"))
        {
            Write-Verbose "Creating the file $Name"
            New-Item -Path "$Path\$Name" -ItemType File
        }

    } # END: Function Test-ErrorLog

# End Support Functions

    # Verify that the error log is present.
    Test-ErrorLog -Path c:\ps\error -Name Errorlog.csv

    # If -NoAppend is TRUE, then clear the error log.
    If(($NoAppend))
    {
        Write-Verbose "Clearing the error log"
        Remove-Item -Path C:\PS\error\ErrorLog.csv -Force
        New-Item -Path C:\PS\error -Name ErrorLog.csv -ItemType File     
    }

    ForEach ($Name in $Names)
    {
        Try {Get-ADUser -Identity $Name -ErrorAction Stop}
        Catch {}
    }

} # END: Function Test-ADUsers

Test-ADUsers -Names "Administrator", "Bad" , "Administrator"  -NoAppend -Verbose


-NoAppend is a switch parameter.  We simply test to see if it is used or not.  If it is, we remove the old file and then create a new one in its place.  This allows us to start with a clean error log whenever we need to.  Go ahead and give it a try.  Make sure you open the error log to verify that it is either appending, or being cleared.

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