Functions/Uninstall-ScheduledTask.ps1

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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

function Uninstall-ScheduledTask
{
    <#
    .SYNOPSIS
    Uninstalls a scheduled task on the current computer.
 
    .DESCRIPTION
    The `Uninstall-ScheduledTask` function uses `schtasks.exe` to uninstall a scheduled task on the current computer. If the task doesn't exist, nothing happens.
 
    .LINK
    Get-ScheduledTask
 
    .LINK
    Test-ScheduledTask
 
    .LINK
    Install-ScheduledTask
 
    .EXAMPLE
    Uninstall-ScheduledTask -Name 'doc'
 
    Demonstrates how to delete a scheduled task named `doc`.
 
    .EXAMPLE
    Uninstall-ScheduledTask -Name 'doc' -Force
 
    Demonstrates how to delete a scheduled task that is currently running.
    #>

    [CmdletBinding(DefaultParameterSetName='AsBuiltinPrincipal')]
    param(
        [Parameter(Mandatory=$true)]
        [Alias('TaskName')]
        [string]
        # The name of the scheduled task to uninstall.
        $Name
    )

    Set-StrictMode -Version 'Latest'

    Use-CallerPreference -Cmdlet $PSCmdlet -Session $ExecutionContext.SessionState

    $Name = Join-Path -Path '\' -ChildPath $Name

    $MAX_TRIES = 5
    $tryNum = 0
    do
    {
        if( -not (Test-ScheduledTask -Name $Name) )
        {
            Write-Verbose ('Scheduled task ''{0}'' not found.' -f $Name)
            return
        }

        $lastTry = (++$tryNum -ge $MAX_TRIES)
        Write-Verbose ('Deleting scheduled task ''{0}''.' -f $Name)
        $errFile = Join-Path -Path $env:TEMP -ChildPath ('Carbon+Uninstall-ScheduledTask+{0}' -f ([IO.Path]::GetRandomFileName()))
        schtasks.exe /delete /tn $Name '/F' 2> $errFile | ForEach-Object { 
            if( $_ -match '\bERROR\b' )
            {
                if( $lastTry -or $err -notmatch 'The function attempted to use a name that is reserved for use by another transaction' )
                {
                    Write-Error $_
                }
            }
            elseif( $_ -match '\bWARNING\b' )
            {
                Write-Warning $_
            }
            else
            {
                Write-Verbose $_
            }
        }

        if( $LASTEXITCODE )
        {
            $err = (Get-Content -Path $errFile) -join ([Environment]::NewLine)
            if( -not $lastTry -and $err -match 'The function attempted to use a name that is reserved for use by another transaction' )
            {
                if( $Global:Error.Count -gt 0 )
                {
                    $Global:Error.RemoveAt(0)
                }
                if( $Global:Error.Count -gt 0 )
                {
                    $Global:Error.RemoveAt(0)
                }                    
                Write-Verbose ('Failed to delete scheduled task ''{0}'' (found ''The function attempted to use a name that is reserved for use by another transaction.'' error). Retrying (attempt #{1}).' -f $Name,$tryNum)
                Start-Sleep -Milliseconds 100
                continue
            }

            Write-Error $err
            break
        }
    }
    while( $true -and -not $lastTry)
}