PowerShell v 3.0 Foreach-Object Changes
I want to draw your attention to changes to Foreach-Object in PowerShell 3.0, while highlighting the differences between the Foreach statement and the Foreach-Object cmdlet.
Topics for PowerShell 3.0’s Foreach-Object Loop
- Foreach-Object in PowerShell 2.0
- Foreach-Object in PowerShell 3.0
- Foreach Statement
- More on PowerShell Foreach
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Foreach-Object in PowerShell 2.0
This is the first half of my experiment:
# PowerShell 2.0 version of Foreach-Object
Clear-host
$Prog =Get-ChildItem ‘C:\program files\*.*’ -recurse
Measure-Command {$Prog | Foreach-Object {$_.name}
}
Note 1: My result was 170 ms.
Note 2: You could use the percentage sign as an alias % {$_.name}
Foreach-Object in PowerShell 3.0
The whole point is that in PowerShell 3.0 you don't need the {curly brackets}. I don't approve of this shortcut, in my mind it's only going to lead to confusion.
# PowerShell 3.0 version of Foreach-Object
Clear-host
$Prog =Get-ChildItem ‘C:\program files\*.*’ -recurse
Measure-Command {$Prog | Foreach-Object $_.name
}
Note 3: My result was the same: 170 ms; removing the brackets made no difference.
Conclusion: Not a big deal, PowerShell 3.0 allows you to remove the {} in the block. We are comparing {$_.name} with $_.name.
Scripting Rationale
The whole rationale of scripting is speed up manual operations. Thus, one of the key elements is looping through a set of instructions while applying a script block to each item.
PowerShell 3.0 loops have simpler syntax compared with versions 1 and 2. As a result beginners can create loops more easily, yet old-timers can reiterate using the same constructions they used in PowerShell 1.0.
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Foreach Statement
Purely to compare and contrast with the examples above, here is the simpler statement version. Its main benefit is speed.
Clear-Host
$Prog = Get-ChildItem ‘C:\program files\*.*’ -recurse
Measure-Command {Foreach ($item in $Prog) {$_.name}}
Note 4: My result was 16.561 ms
With the Foreach statement you cannot use the % alias.
If you get an error message test this snippet:
Get-ChildItem ‘C:\program files\*.*’ -recurse
See more on PowerShell Measure-Command ยป
Recap of PowerShell’s Foreach Loop
Let us examine the PowerShell 2.0 loop syntax:
Foreach ($item in $collection-array) {command_block}.
Foreach is the PowerShell instruction to cycle or repeat; it feeds on an array of ($items in $collection-array) then you need a {Block statement payload}.
One more tiny, but crucial, component of the PowerShell foreach loop is ‘in’.
Simple PowerShell Foreach
# PowerShell Foreach Example
Clear-Host
Foreach ($number in 1..10 ) { $number * 25}
See examples of PowerShell v 3.0’s where »
Summary of PowerShell Foreach-Object Loops
In PowerShell 3.0 the Where-Object and Foreach-Object have made adding a set of {Curly} brackets optional. The idea is to make the scripts easier to write for beginners. However, you will notice many old-times still use the version 2.0 fuller syntax.
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See more Windows PowerShell examples
• PowerShell Home • Foreach loops • PowerShell Foreach • Foreach-Object cmdlet
• Syntax • Variables • -whatIf • -ErrorAction • Windows 8 PowerShell • Free CSV Import Tool
• PowerShell Functions • [System.Math] • Get-Credential • Windows PowerShell • PowerShell 3.0
Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.
