I wrote a very simple script to acquire a random free drive letter.
The function finds a random free letter , creates a new empty text file of that drive letter name eg. Q.txt
I then return the value as $new_letter but when it comes out of the function somehow newly file created path is a part of the variable C:\AppPack\Logs\Q.txt Q
Is it something New-Item
messing up with my $new_letter
variable ?
function get_drive_letter()
{
$letter_acquired = $false
Do
{
$new_letter = Get-ChildItem function:[h-z]: -Name | ForEach-Object { if (!(Test-Path $_)){$_} } | random -Count 1 | ForEach-Object {$_ -replace ':$', ''}
write-host ("RIGHT AFTER " + $new_letter)
if (!(test-path "C:\AppPack\Logs\$new_letter.txt"))
{
New-Item -Path C:\AppPack\Logs\ -Name "$new_letter.txt" -ItemType "file"
write-host ("FROM FUNCTION " + $new_letter)
$letter_acquired = $true
return $new_letter
}
else
{
write-host ("LETTER USED ALREADY")
write-host ($new_letter)
}
}
while($letter_acquired = $false)
}
$drive_letter = $null
$drive_letter = get_drive_letter
write-host ("RIGHT AFTER FUNCTION " + $drive_letter)
OUTPUT :
RIGHT AFTER Q
FROM FUNCTION Q
RIGHT AFTER FUNCTION C:\AppPack\Logs\Q.txt Q
A PowerShell function outputs everything, not just the result of the expression right after
return
!The additional file path you see is the output from
New-Item ...
- it returns aFileInfo
object for the file you just created.You can suppress output by assigning it to the special
$null
variable:Or by piping to
Out-Null
:Or by casting the entire pipeline to
[void]
:Although I recommend explicitly handling unwanted output at the call site, you can also work around this behavior with a hoisting trick.
To demonstrate, consider this dummy function - let's say we "inherit" it from a colleague who didn't always write the most intuitive code:
The function above will output 3 objects - the two garbage strings one-by-one, followed by the result that we're actually interested in:
Let's say we've been told to make as few modifications as possible, but we really need to suppress the garbage output.
To do so, nest the entire function body in a new scriptblock literal, and then invoke the whole block using the dot-source operator (
.
) - this forces PowerShell to execute it in the function's local scope, meaning any variable assignments persist: