Touch Command in PowerShell

Sun, Aug 20 2017

The two simplest use cases for the touch command are to:

Create one or more files, if they don’t exist;
Update the access date or modification date of files without changing their content.

To replicate these two cases in PowerShell, we make use of the LastWriteTime property of a FileSystemInfo object, as well as creating an empty file if one does not exist at the specified path.

You can add the following code to the Microsoft.PowerShell_profile.ps1 file in your <Users>\Documents\WindowsPowerShell\ folder:

	Function Update-File
	{
	$Usage = "Usage: Update-File [file1 ... fileN]";
	# if no arguments, display an error
	if ($args.Count -eq 0) {
	throw $Usage;
	}
	# see if any arguments match -h[elp] or --h[elp]
	foreach($file in $args) {
	if ($file -ilike "-h" -or $file -ilike "--h") {
	echo $Usage;
	return;
	}
	}

	foreach($file in $args) {
	if(Test-Path -LiteralPath $file)
	{
	# file exists, update last write time to now
	@setProps = @{
	LiteralPath = $file
	Name = 'LastWriteTime'
	Value = (Get-Data)
	}
	Set-ItemProperty @setProps
	}
	else
	{
	# create new file.
	# don't use `echo $null > $file` because it creates an UTF-16 (LE)
	# and a lot of tools have issues with that
	echo $null \| Out-File -Encoding ascii -LiteralPath $file
	# alternative
	# New-Item -Path $file -ItemType File \| Out-Null
	}
	}
	}
	New-Alias -Name touch -Value Update-File

view raw Update-File.ps1 hosted with ❤ by GitHub

You can now call it with either: Update-File file1.txt file2.txt or touch file1.txt file2.txt.

Couple of Points Worth Making

We name the function Update-File following the PowerShell pattern or verb-noun pair for commands and the Data Verbs section of Approved Verbs for Windows PowerShell Commands.

We set pass the -Encoding ascii to the Out-File command as the default encoding for Out-File is UTF-16 and some *nix transplant tools have troubles handling UTF-16 files because of the two byte-markers at the beginning of the file (for example webpack when bundling files).

Finally, credit goes to this answer on StackExchange’s superuser.