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How do I strip out everything but numbers in a variable?

I am trying to automate the setting of an IP address through PowerShell and I need to figure out what my interface number is.

I have developed the following:

$x = ( Get-NetAdapter |
       Select-Object -Property InterfceName,InterfaceIndex |
       Select-Object -First 1 |
       Select-Object -Property Interfaceindex ) | Out-String

This will output:

InterfaceIndex
--------------
             3

Now the problem is when I try to grab just a number using:

$x.Trim.( '[^0-9]' )

it still leaves "InterfaceIndex" and underscores. This throws the next part of my script error because I just need a number.

Any suggestions?

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3 answers


This will do your job:

( Get-NetAdapter | Select-Object -Property InterfceName,InterfaceIndex | Select-Object -First 1 | Select-Object -Property Interfaceindex).Interfaceindex


You don't actually need to double-select a property: do it like this:

( Get-NetAdapter |Select-Object -First 1| Select-Object -Property InterfceName,InterfaceIndex).Interfaceindex
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(Get-NetAdapter | select -f 1).Interfaceindex

There is no point in choosing the default properties. If you want to save the object, follow these steps:

(Get-NetAdapter | select -f 1 -ov 'variablename').Interfaceindex


where f = first, ov = outvariable

$variablename.Interfaceindex

You don't need to Out-String

, as the cast to string is implicit on display. and if you try to work with that data further, PowerShell is smart enough to cast it from int to string and vice versa when needed.

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Answering your question, you can remove everything that is not a number from a variable by removing everything that is not a number (or rather a digit):

$x = $x -replace '\D'

However, your best bet would be to simply not add what you want to remove in the first place:

$x = Get-NetAdapter | Select-Object -First 1 -Expand InterfaceIndex

PowerShell cmdlets usually produce objects as output, so instead of treating those objects in inline form and stripping out the extra stuff, you usually just expand the value of the object you're interested in.

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