CODEWITHSUNDEEP
powershell
cloudnyn3
cloudnyn3

Reputation: 897

PowerShell "Period" operator, what does it do?

I've been looking online for a specific answer to better help me understand how this works. In PHP we use the " . " to concatenate strings. However in powershell I see things like this:

    Dir | where {$_.extension -eq ".txt"} | 
    Rename-Item –NewName { $_.name –replace “.“,”-” }

I can see that the "Dir" command is piped to "Where" but, I don't understand what its defining a variable for using:

    $_.extension

Is this a way of adding extra operators to a function?? I'm pretty confused. I'm getting better but, I need to know how exactly periods and the $_. work when using the cmdlets and what not.

Any help is appreciated.

Upvotes: 0

Views: 1114

Answers (3)

mjolinor
mjolinor

Reputation: 68273

Powershell has very good help files included that can answer many questions.

See:

get-help about_operators

and you will find that the dot is used as both a Property dereferencing operator and a scope operator, with explanations of the use of each.

Can also see this under about_operators on TechNet

Upvotes: 6

kravasb
kravasb

Reputation: 696

DIR command is similar to Get-ChildItem command. The | is similar to foreach statement. The $_ sign indicates each element in foreach loop. In your case, the code should get all which have .txt extension from some location and then rename each of those elements due to { $_.name –replace “.“,”-” } rule

Upvotes: 0

Richard Cook
Richard Cook

Reputation: 33089

It's the member access operator. $_ is a special variable (the loop variable in this case). Therefore, $_.extension accesses or invokes the property extension on $_.

Upvotes: 2

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