Change the access and modification times of one or more files.

Set-File.ps1

#Requires -Version 3.0

<#
.SYNOPSIS
    Change the access and modification times of one or more files.

.DESCRIPTION
    Set-File is designed to work in similar fashion to the Unix 'touch(1)' command. If the given filepath does 
    not exist, Set-File creates the file setting its initial content to $null. If the file already exists then 
    some or all of the file's timestamps can be modified. Unless specific properties are specified an existing
    file's CreationTime, LastAccessTime, and LastWriteTime properties will be modified. A specific date can be 
    used or a reference file can be provided from which to clone a timestamp from. If neither a date or file 
    is provided the default date is set to the current time.

.NOTES
    Author   : Lido Paglia <lido@paglia.org>
    Date     : 12/31/2013 10:18:28
    Tags     : file, path, touch, date, timestamp
    Comments :
    
.PARAMETER FilePath
    One or more files to modify.

.PARAMETER Property
    The specific timestamp property to modify. Properties include LastWriteTime, LastAccessTime, and CreationTime. 
    The default behavior will modify all three properties if a single property is not provided.

.PARAMETER Date
    A specific datetime object to use for modifying one or more file timestamps. If a date is not specified the 
    current time will be used.

.PARAMETER ReferenceFile
    A path to a reference file from which to clone a timestamp from. Similar to -r, --reference=FILE
    in touch(1).

.PARAMETER ReferenceProperty
    The timestamp to use from the given reference file. This parameter is mandatory if -FileDate is specified. 
    Available options are: LastAccessTime, LastWriteTime, or CreationTime.

.PARAMETER PassThru
    Passes an FileInfo object representing the modified item to the pipeline. By default, this script cmdlet does 
    not generate any output.

.PARAMETER Force
    Allows overwriting an existing read-only file. If the file path specified does not exist using -Force will create the 
    file including any non-existent directories in the specified path. Even using the Force parameter, the cmdlet cannot 
    override filesystem security restrictions.

.INPUTS
    System.String. You can pipe a list of objects to Set-File to operate on.

.OUTPUTS
    None or an object representing the new or changed item.
    
    When you use the Passthru parameter, Set-File generates an object representing the modified item. 
    Otherwise, this cmdlet does not generate any output.

.EXAMPLE
    touch .\foo\bar\bat -Force

    Creates the file 'bat' in the folder path '.\foo\bar' in the current working directory.

.EXAMPLE
    touch -FilePath foo.txt -Date (Get-Date).AddDays(-2)

.EXAMPLE
    Get-ChildItem f* -File | touch -PassThru

    Gets all files beginning with the letter 'f' in the current working directory and sets their LastWriteTime, 
    LastAccessTime, and CreationTime to the current time and passes their fileinfo objects to the pipeline.

.EXAMPLE
    ls f* -File | touch -Property LastWriteTime -Date (Get-Date 12/20/1990)

    Gets all files beginning with the letter 'f' in the current working directory and sets their LastWriteTime
    to the specified date, 12/20/1990

.LINK
    Set-Content

.LINK
    New-Item

.LINK
    http://en.wikipedia.org/wiki/Touch_(Unix)

.LINK
    http://sushihangover.blogspot.com/2012/10/powershell-true-touch-file-routine.html

.LINK
    http://stackoverflow.com/questions/3038337/powershell-resolve-path-that-might-not-exist

#>

function Set-File
{
    [cmdletbinding(SupportsShouldProcess)]
    
    Param(
        [Parameter(Mandatory,Position=0,ValueFromPipeline,ValueFromPipelineByPropertyName,HelpMessage="Which file to create or modify?")]
        [Alias("FullName")]
        [String[]]$FilePath,

        [ValidateSet("All","LastAccessTime","LastWriteTime","CreationTime")]
        [String]$Property = "All",
        
        [Parameter(ParameterSetName='DateFromArgs')]
        [DateTime]$Date,

        [Parameter(ParameterSetName='DateFromFile')]
        [ValidateScript({Test-Path $_ -PathType Leaf})]
        [String]$ReferenceFile,

        [Parameter(Mandatory,ParameterSetName='DateFromFile',HelpMessage="Which of the reference file's attributes to use? (LastAccessTime, LastWriteTime, or CreationTime)")]
        [ValidateSet("LastAccessTime","LastWriteTime","CreationTime")]
        [String]$ReferenceProperty,

        [Switch]$PassThru,

        [Switch]$Force
    )

    begin
    {
        #region 'Domestic Workers'

        function updateFileSystemInfo
        {
            [cmdletbinding()]
            Param(
                [Parameter(Mandatory,Position=0)]
                [System.IO.FileSystemInfo]$InputObject,

                [ValidateSet("All","LastAccessTime","LastWriteTime","CreationTime")]
                [String]$Property = "All",
                
                [Parameter(Mandatory,Position=1)]
                [DateTime]$Date,
                
                [Switch]$PassThru
            )

            switch ($Property) {
                  'CreationTime' { $InputObject.CreationTime   = $FileTime }
                'LastAccessTime' { $InputObject.LastAccessTime = $FileTime }
                 'LastWriteTime' { $InputObject.LastWriteTime  = $FileTime }
                         Default { $InputObject.CreationTime   = $FileTime
                                   $InputObject.LastAccessTime = $FileTime
                                   $InputObject.LastWriteTime  = $FileTime }
            } #endswitch
           
            if($PassThru)
            {
                $InputObject
            }
        }
        
        function touchNewFile
        {
            [cmdletbinding()]
            Param(
                [String]$FilePath,
                [Switch]$Force
            )

            $ParentPathExists = (Test-Path -Path (Split-Path $FilePath -Parent))

            if($ParentPathExists)
            {
                Set-Content -Path $FilePath -Value $null -Force:$Force
            }
            elseif((-Not($ParentPathExists)) -and $Force)
            {
                mkdir (Split-Path $FilePath -Parent) -Force -Confirm:$false | Out-Null
                Set-Content -Path $FilePath -Value $null -Confirm:$false -Force:$Force
            }
            else
            {
                Write-Error "Ensure the path `"$FilePath`" exists or use the -Force Parameter."
            }
        }

        function getFileTime
        {
            Param(
                [ValidateScript({Test-Path $_ -PathType Leaf})]
                [String]$FilePath,
                
                [ValidateSet("LastAccessTime","LastWriteTime","CreationTime")]
                [String]$Property = "CreationTime"
            )

            switch ($Property)
            {
                'CreationTime'   {(Get-ChildItem -Path $FilePath).CreationTime}
                'LastAccessTime' {(Get-ChildItem -Path $FilePath).LastAccessTime}
                'LastWriteTime'  {(Get-ChildItem -Path $FilePath).LastWriteTime}
            }
        }

        #endregion

        #region 'Hey, wanna go on a date?'
        
        if($Date)
        {
            $FileTime = $Date
        }
        elseif($ReferenceFile)
        {
            $FileTime = getFileTime -FilePath $ReferenceFile -Property:$ReferenceProperty
        }
        else
        {
            $FileTime = Get-Date
        }

        $updateParams = @{Date=$FileTime;Property=$Property;ErrorAction='Stop'}

        #endregion
    }
    process
    {
        foreach($Path in $FilePath)
        {
            #http://stackoverflow.com/questions/3038337/powershell-resolve-path-that-might-not-exist
            $File = $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath("$Path")
            
            if(Test-Path $File)
            {
                if($PSCmdlet.ShouldProcess($File, "Modify File"))
                {
                    updateFileSystemInfo -InputObject (Get-ChildItem $File) @updateParams -PassThru:$PassThru
                }
            }
            else
            {
                if($PSCmdlet.ShouldProcess($File, "Create File"))
                {
                    try
                    {
                        touchNewFile -FilePath $File -Force:$Force -ErrorAction Stop
                    }
                    catch
                    {
                        Write-Error "Ensure the path `"$FilePath`" exists or use the -Force Parameter."
                        break;
                    }

                    updateFileSystemInfo -InputObject (Get-ChildItem $File) @updateParams -PassThru:$PassThru
                }
            }
        }
    }
}

Set-Alias -Name touch -Value Set-File