Estimated Completion Time and Progress Bar in Powershell

<h1>Estimated Completion Time in PowerShell</h1>

Progress Bars are all about giving the user feedback as to what the program is doing, and Powershell implements it with the Write-Progress cmdlet. It is also possible to predict the completion time by using a little math.

Possible uses for the progress bar include:

  1. Showing status of reading a large file
  2. Showing status of exploding a directory structure
  3. Showing progress of creating files or videos
  4. Showing status of processing a large number of database records
  5. Showing status of file upload or download

In my opinion, a status bar should not just show the progress, but also tell the user the estimated completion time (sometimes called ETA – Estimated Time of Arrival). This is done by computing a ratio of the word done to the work to be performed, and using that ratio along with elapsed time and TimeSpans to come up with the estimated completion time.

$maxI = 250 
$startTime = get-date 
Write-Host "StartTime=$startTime"
for ($i = 1; $i -le $maxI; $i++ )
  write-host "`$i=$i"
  start-sleep -milliseconds 250  
  $elapsedTime = $(get-date) - $startTime 

  #do the ratios and "the math" to compute the Estimated Time Of Completion 
  $estimatedTotalSeconds = $maxI / $i * $elapsedTime.TotalSeconds 
  $estimatedTotalSecondsTS = New-TimeSpan -seconds $estimatedTotalSeconds
  $estimatedCompletionTime = $startTime + $estimatedTotalSecondsTS
  Write-Host "elapsedTime=$($elapsedTime.TotalSeconds) estimatedTotalSeconds=$estimatedTotalSeconds"
  Write-Host "estimatedCompletionTime=$estimatedCompletionTime"

  #I like to keep the width of the Write-Progress minimalized by creating three variables 
  #and substituting them into the Write-Progress statement. 
  $activityMsg = "Search in Progress"
  $percentComplete = $i / $maxI * 100 
  $statusMsg = "$percentComplete% Complete: $i out of $maxI Estimated Completion at $estimatedCompletionTime"

  write-progress -activity $activityMsg -status $statusMsg  -percentcomplete $percentComplete;
  Write-host "percent complete=$percentComplete "
$endTime = get-date 
$elapsedTime = $endTime - $startTime 
write-host "The End $startTime=$startTime endTime=$endTime elapseSeconds=$($elapsedTime.TotalSeconds)"

write-host "The End" 

Running in ISE, the progress bar looks like this (it actually seems to hide the first few lines in the output pane).


The command line version is not quite as pretty, but still effective:

WindowsClockI suggest you take this example, change the value of $maxI and/or change the sleep time, and see if you get an accurate prediction of the completion time.


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