Backs up a source folder path to a given destination folder with some logic to define time stamped folders and preserve file system space by recycling older back-up folders where the -AppendDateTime argument is used.

SimpleBackup.ps1

# SimpleBackup.ps1
# Written by A Hendley (ahendley@internode.on.net)
#
# A simple back-up of a source folder path to a given destination folder path.

<#
.SYNOPSIS
Backs up a source folder path to a given destination folder with some logic to
define time stamped folders and preserve file system space by recycling older
back-up folders where the -AppendDateTime argument is used.

.DESCRIPTION
Backs up a source folder path to a given destination folder with some logic to
define time stamped folders and preserve file system space by recycling older
back-up folders where the -AppendDateTime argument is used.

To protect the integrity of a past back-up or destination folder, the command
will not overwrite the contents and throw an error. To ensure this does not
happen, use the -AppendDateTime argument.

.PARAMETER Path
Specifies the source path to be backed up.

.PARAMETER Destination
Specifies the destination path to back-up too.

.PARAMETER AppendDateTime
Specifies whether to append a date and time folder to the end of the
destination path.

.PARAMETER Recycle
Specifies if back-up folders are to be recycled when used with -AppendDateTime.
Helps preserve disk space.

.PARAMETER RecycleCount
Specifies how many back-ups to keep when used with -AppendDateTime and
-Recycle. Default value is 2.

.EXAMPLE
C:\>SimpleBackup.ps1 -Path "C:\My\Source\Folder" -Destination "C:\My\Backups" -AppendDateTime -Recycle -RecycleCount 2
This command will backup the source folder to a new folder with a date and time
format of (yyyyMMdd_HHmmss) under the destination folder. The command will also
remove any previous back-up folders while retaining the current and previous
back-up.

.EXAMPLE
C:\>SimpleBackup.ps1 -Path "C:\My\Source\Folder" -Destination "C:\My\Backups"
This command will back-up the source folder directly into the specified
destination folder.
#>

[CmdletBinding(DefaultParameterSetName="Path", SupportsShouldProcess=$false)]
param (
    [Parameter(Position=0, Mandatory=$true, HelpMessage="Specifies the source path to be backed up.")]
    [string] $Path,
    [Parameter(Position=1, Mandatory=$true, HelpMessage="Specifies the destination path to back-up too.")]
    [string] $Destination,
    [Parameter(Position=2, Mandatory=$false, HelpMessage="Specifies whether to append a date and time folder to the end of the destination path.")]
    [switch] $AppendDateTime,
    [Parameter(Position=3, Mandatory=$false, HelpMessage="Specifies if back-up folders are to be recycled when used with -AppendDateTime. Helps preserve disk space.")]
    [switch] $Recycle,
    [Parameter(Position=4, Mandatory=$false, HelpMessage="Specifies how many back-ups to keep when used with -AppendDateTime and -Recycle. Default value is 2.")]
    [int] $RecycleCount = 2
)

begin {
}
process {
    if ($AppendDateTime) {
        $datetime_string = get-date -format "yyyyMMdd_HHmmss"
        $finalDestination = [System.IO.Path]::Combine($Destination, $datetime_string)
    } else {
        $finalDestination = $Destination
    }

    if (Test-Path $finalDestination) {
        throw "The destination path ($finalDestination) already exists which is not allowed."
    }

    Copy-Item -Path $Path -Destination $finalDestination -Recurse -Force
   
    write-host "Path - $Path"
    write-host "  > Backed up to - $finalDestination"

    if ($AppendDateTime -And $Recycle) {
        $folder_count = (dir $Destination | where {$_.PsIsContainer} | Measure-Object Name).Count

        if ($folder_count -gt $RecycleCount) {
            $remove_count = ($folder_count - $RecycleCount)
            $folders_to_remove = (dir $Destination | where {$_.PsIsContainer} | sort-object FullName | select FullName -First $remove_count | foreach {$_.FullName})

            ForEach ($f in $folders_to_remove -Split "`n") {
                $folder = $f.Replace("`r", "")

                write-host "Removing old back-up folder - $folder"
                Remove-Item -Path $folder -Force -Recurse
            }
        }
    }
}
end {
}