Powershell Countdown Timer

Update: Feb 22, 2011: Click here for my New and Improved Countdown timer

I often run Powershell scripts that run in a continuous loop to monitor some process or watch for some event to happen. The script could be reading a database, watching active processes, services or whatever but I don’t necessarily need to thrash the system or overburden a database with non-stop processing or database queries. The easy solution to this is to use the start-sleep cmdlet which works fine, but doesn’t provide any user feadback while in the “sleep” state.

I developed the following function for console feedback in instances where the sleep time is more than just a few seconds. By using the “`r” (carriage return) escape sequence in combination with the “write-host -nonewline”, I can keep the countdown timer display on a single console line with no scrolling. Also, by using foreground and background color highlighting, a nice visual cue is added, making the user interface very easy to read at a quick glance.

To achieve this, I use some simple date arithmetic and the time-span cmdlet. The Countdown function will sleep for one second at a time and wake up long enough to display an updated countdown timer in the form of “hours:minutes:seconds”. The trick is to clear the countdown timer line by overwriting with spaces and positioning the cursor back to the beginning of the line before writing the updated time-span data.

Here’s the basic steps that occur within the countdown timer.

        $startTime = get-date
        $endTime   = $startTime.addMinutes($waitMinutes)
        $timeSpan = new-timespan $startTime $endTime

        write-host "`r".padright(40," ") -nonewline

        write-host $([string]::Format("`rTime Remaining: {0:d2}:{1:d2}:{2:d2}", `
            $timeSpan.hours, `
            $timeSpan.minutes, `
            $timeSpan.seconds)) `
            -nonewline -backgroundcolor black -foregroundcolor yellow

Time Remaining: 00:01:00

function CountDown($waitMinutes) {
    $startTime = get-date
    $endTime   = $startTime.addMinutes($waitMinutes)
    $timeSpan = new-timespan $startTime $endTime
    write-host "`nSleeping for $waitMinutes minutes..." -backgroundcolor black -foregroundcolor yellow
    while ($timeSpan -gt 0) {
        $timeSpan = new-timespan $(get-date) $endTime
        write-host "`r".padright(40," ") -nonewline
        write-host $([string]::Format("`rTime Remaining: {0:d2}:{1:d2}:{2:d2}", `
            $timeSpan.hours, `
            $timeSpan.minutes, `
            $timeSpan.seconds)) `
            -nonewline -backgroundcolor black -foregroundcolor yellow
        sleep 1
        }
    write-host ""
    }
 
while (-1) {
    write-host "doing some work....."
    Countdown 1
    }

Sleeping for 1 minutes...
 Time Remaining: 00:00:59