What does $_ mean in powershell?

Question

I've seen this alot in powershell but not sure what exactly it does:

$_

Answer 1

According to this website, it's a reference to this, mostly in loops.

$_ (dollar underscore) 'THIS' token. Typically refers to the item inside a foreach loop. Task: Print all items in a collection. Solution. ... | foreach { Write-Host $_ }

Answer 2

This is the variable for the current value in the pipe line.

1,2,3 | %{ write-host $_ } 

For example in the above code the %{} block is called for every value in the array. The $_ variable will contain the current value.

Answer 3

See http://www.computerperformance.co.uk/powershell/powershell_variables.htm#Special_$__Variable

Answer 4

It's the reference to the piped-in value.

It's similar to this in C# or Me in VB

Answer 5

I think the easiest way to think about this variable like input parameter in lambda expression in C#. I.e. $_ is similar to x in x => Concole.WriteLine(x) anonymous function in C#. Consider following examples:

PowerShell:

1,2,3 | ForEach-Object {Write-Host $_}

Prints:

1
2
3

or

1,2,3 | Where-Object {$_ -gt 1}

Prints:

2
3

And compare this with C# syntax using LINQ:

var list = new List<int> { 1, 2, 3 };
list.ForEach( _ => Console.WriteLine( _ ));

Prints:

1
2
3

or

list.Where( _ => _ > 1)
    .ToList()
    .ForEach(s => Console.WriteLine(s));

Prints:

2
3

Answer 6

$_ is an variable which iterates over each object/element passed from the previous | (pipe).