Waiting for user input with a timeout

Question

I have searched but apparently my google foo is weak. What I need is a way to prompt for user input in the console and have the request time out after a period of time and continue executing the script if no input comes in. As near as I can tell, Read-Host does not provide this functionality. Neither does $host.UI.PromptForChoice() nor does $host.UI.RawUI.ReadKey(). Thanks in advance for any pointers.

EDIT: Much thanks to Lars Truijens for finding the answer. I have taken the code that he pointed out and encapsulated it into a function. Note that the way that I have implemented it means there could be up to one second of delay between when the user hits a key and when script execution continues.

function Pause-Host
{
    param(
            $Delay = 1
         )
    $counter = 0;
    While(!$host.UI.RawUI.KeyAvailable -and ($counter++ -lt $Delay))
    {
        [Threading.Thread]::Sleep(1000)
    }
}

Answer 1

Found something here:

$counter = 0
while(!$Host.UI.RawUI.KeyAvailable -and ($counter++ -lt 600))
{
      [Threading.Thread]::Sleep( 1000 )
}

Answer 2

It's quite old now but how I solved it based on the same KeyAvailable method is here:

https://gist.github.com/nathanchere/704920a4a43f06f4f0d2

It waits for x seconds, displaying a . for each second that elapses up to the maximum wait time. If a key is pressed it returns $true, otherwise $false.

Function TimedPrompt($prompt,$secondsToWait){   
    Write-Host -NoNewline $prompt
    $secondsCounter = 0
    $subCounter = 0
    While ( (!$host.ui.rawui.KeyAvailable) -and ($count -lt $secondsToWait) ){
        start-sleep -m 10
        $subCounter = $subCounter + 10
        if($subCounter -eq 1000)
        {
            $secondsCounter++
            $subCounter = 0
            Write-Host -NoNewline "."
        }       
        If ($secondsCounter -eq $secondsToWait) { 
            Write-Host "`r`n"
            return $false;
        }
    }
    Write-Host "`r`n"
    return $true;
}

And to use:

$val = TimedPrompt "Press key to cancel restore; will begin in 3 seconds" 3
Write-Host $val

Answer 3

For people who are looking for a modern age solution with an additional constraint for exiting a PowerShell script on a pre-defined key press, the following solution might help you:

Write-Host ("PowerShell Script to run a loop and exit on pressing 'q'!")
$count=0
$sleepTimer=500 #in milliseconds
$QuitKey=81 #Character code for 'q' key.
while($count -le 100)
{
    if($host.UI.RawUI.KeyAvailable) {
        $key = $host.ui.RawUI.ReadKey("NoEcho,IncludeKeyUp")
        if($key.VirtualKeyCode -eq $QuitKey) {
            #For Key Combination: eg., press 'LeftCtrl + q' to quit.
            #Use condition: (($key.VirtualKeyCode -eq $Qkey) -and ($key.ControlKeyState -match "LeftCtrlPressed"))
            Write-Host -ForegroundColor Yellow ("'q' is pressed! Stopping the script now.")
            break
        }
    }
    #Do your operations
    $count++
    Write-Host ("Count Incremented to - {0}" -f $count)
    Write-Host ("Press 'q' to stop the script!")
    Start-Sleep -m $sleepTimer
}
Write-Host -ForegroundColor Green ("The script has stopped.")

Sample script output:

Refer Microsoft document on key states for handling more combinations.

Credits: Technet Link

Answer 4

timeout.exe 5

still works from powershell. Waits 5 seconds or until key press.

Inelegant perhaps. But easy.

However,

From the Powershell_ISE it pops up a new command prompt window, and returns immediately, so it doesnt wait (From the powershell console it uses that console and does wait). You can make it wait from the ISE with a little more work (still pops up its own window tho):

if ($psISE) {
    start -Wait timeout.exe 5
} else {
    timeout.exe 5
}

Answer 5

Here is a keystroke utility function that accepts:

• Validation character set (as a 1-character regex).
• Optional message
• Optional timeout in seconds

Only matching keystrokes are reflected to the screen.

Usage:

$key = GetKeyPress '[ynq]' "Run step X ([y]/n/q)?" 5

if ($key -eq $null)
{
    Write-Host "No key was pressed.";
}
else
{
    Write-Host "The key was '$($key)'."
}

Implementation:

Function GetKeyPress([string]$regexPattern='[ynq]', [string]$message=$null, [int]$timeOutSeconds=0)
{
    $key = $null

    $Host.UI.RawUI.FlushInputBuffer() 

    if (![string]::IsNullOrEmpty($message))
    {
        Write-Host -NoNewLine $message
    }

    $counter = $timeOutSeconds * 1000 / 250
    while($key -eq $null -and ($timeOutSeconds -eq 0 -or $counter-- -gt 0))
    {
        if (($timeOutSeconds -eq 0) -or $Host.UI.RawUI.KeyAvailable)
        {                       
            $key_ = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown,IncludeKeyUp")
            if ($key_.KeyDown -and $key_.Character -match $regexPattern)
            {
                $key = $key_                    
            }
        }
        else
        {
            Start-Sleep -m 250  # Milliseconds
        }
    }                       

    if (-not ($key -eq $null))
    {
        Write-Host -NoNewLine "$($key.Character)" 
    }

    if (![string]::IsNullOrEmpty($message))
    {
        Write-Host "" # newline
    }       

    return $(if ($key -eq $null) {$null} else {$key.Character})
}

Answer 6

function ReadKeyWithDefault($prompt, $defaultKey, [int]$timeoutInSecond = 5 ) {
    $counter =  $timeoutInSecond * 10
    do{
        $remainingSeconds = [math]::floor($counter / 10)
        Write-Host "`r$prompt (default  $defaultKey  in $remainingSeconds seconds): " -NoNewline
        if($Host.UI.RawUI.KeyAvailable){
            $key = $host.UI.RawUI.ReadKey("IncludeKeyUp")
            Write-Host 
            return $key
        }
        Start-Sleep -Milliseconds 100
    }while($counter-- -gt 0)

    Write-Host $defaultKey
    return $defaultKey
}

$readKey = ReadKeyWithDefault "If error auto exit( y/n )" 'y' 5

Answer 7

Another option: you can use choice shell command which comes with every Windows version since Windows 2000

Choice /C yn /D n /t 5 /m "Are you sure? You have 5 seconds to decide"
if ($LASTEXITCODE -eq "1") # 1 for "yes" 2 for "no"
{
    # do stuff
}
else
{
    # don't do stuff
}

Stackoverflow syntax higlighting doesn't work for powershell, # means "comment" here

Answer 8

The $Host.UI.RawUI.KeyAvailable seems to be buggy so I had more luck using [Console]::KeyAvailable:

function keypress_wait {
    param (
        [int]$seconds = 10
    )
    $loops = $seconds*10
    Write-Host "Press any key within $seconds seconds to continue"
    for ($i = 0; $i -le $loops; $i++){
        if ([Console]::KeyAvailable) { break; }
        Start-Sleep -Milliseconds 100
    }
if ([Console]::KeyAvailable) { return [Console]::ReadKey($true); }
else { return $null ;}
}

Answer 9

Flushing Input buffer is very important, try this, worked like a charm for me.

function Pause-Host {
    param ($Delay = 1)
    
    $host.UI.RawUI.FlushInputBuffer()
    While(!$host.UI.RawUI.KeyAvailable -and (0 -lt $Delay--))
    {
        Write-Host "`rWaiting for $Delay Seconds or Any key Press ..." -NoNewline
        Start-Sleep -Seconds 1
    }
}
# Optional: Flush last key-press
$host.UI.RawUI.FlushInputBuffer()

Answer 10

To optionally pause the script before it exits (useful for running headless scripts and pausing on error output), I appended nathanchere's answer with:

if ([Console]::KeyAvailable) { $pressedKey = [Console]::ReadKey($true); read-host; break; }
  elseif ($secondsCounter -gt $secondsToWait) { 
      Write-Host "`r`n"
      return $false;
  }