8.2 Measure the Duration of a Command

Problem

You want to know how long a command takes to execute.

Solution

To measure the duration of a command, use the Measure-Command cmdlet:

PS > Measure-Command { Start-Sleep -Milliseconds 337 }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 0
Milliseconds      : 339
Ticks             : 3392297
TotalDays         : 3.92626967592593E-06
TotalHours        : 9.42304722222222E-05
TotalMinutes      : 0.00565382833333333
TotalSeconds      : 0.3392297
TotalMilliseconds : 339.2297

Discussion

In interactive use, it’s common to want to measure the duration of a command. An example of this might be running a performance benchmark on an application you’ve developed. The Measure-Command cmdlet makes this easy to do. Because the command generates rich object-based output, you can use its output for many date-related tasks. See Recipe 3.8 for more information.

If the accuracy of a command measurement is important, general system activity can easily influence the timing of the result. A common technique for improving accuracy is to repeat the measurement many times, ignore the outliers (the top and bottom 10 percent), and then average the remaining results. Example 8-1 implements this technique.

Example 8-1. Measure-CommandPerformance.ps1

##############################################################################
##
## Measure-CommandPerformance
##
## From PowerShell Cookbook (O'Reilly)
## by Lee Holmes (http://www.leeholmes.com/guide)
##
##############################################################################

<#

.SYNOPSIS

Measures the average time of a command, accounting for natural variability by
automatically ignoring the top and bottom 10%.

.EXAMPLE

PS > Measure-CommandPerformance.ps1 { Start-Sleep -m 300 }

Count    : 30
Average  : 312.10155
(...)

#>

param(
    ## The command to measure
    [Scriptblock] $Scriptblock,

    ## The number of times to measure the command's performance
    [int] $Iterations = 30
)

Set-StrictMode -Version 3

## Figure out how many extra iterations we need to account for the outliers
$buffer = [int] ($iterations * 0.1)
$totalIterations = $iterations + (2 * $buffer)

## Get the results
$results = 1..$totalIterations |
    Foreach-Object { Measure-Command $scriptblock }

## Sort the results, and skip the outliers
$middleResults = $results | Sort TotalMilliseconds |
    Select -Skip $buffer -First $iterations

## Show the average
$middleResults | Measure-Object -Average TotalMilliseconds

For more information about the Measure-Command cmdlet, type Get-Help Measure-Command.

8.2 Measure the Duration of a Command

Problem

Solution

Discussion

Example 8-1. Measure-CommandPerformance.ps1

See Also