PowerShell string interpolation via a variable

Question

The following code works as expected:

'John' | % { "$_ $_" }
> John John

However, I couldn't work out a way of storing the string $_ $_ in a variable, which is later used in the pipeline:

$f = '$_ $_'
'John' | % { $f }
> $_ $_

How would I "interpolate" a variable, instead of using double quoted string?

user189198 · Accepted Answer · 2014-04-08 16:43:04Z

5

You can define a PowerShell ScriptBlock, enclosed in curly braces, and then execute it using the . call operator.

$f = { $_ $_ }
'John' | % { . $f }

Output looks like:

John
John

Or, if you want a single string (like your initial question), you can do:

$f = { "$_ $_" }
'John' | % { . $f };

Output looks like:

John John

answered Apr 8, 2014 at 16:43

user189198

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2 Comments

Why is the semi-colon needed in the second example?

The semicolon is not a requirement, but it delimits the end of a command in PowerShell.

Community · Accepted Answer · 2017-05-23 11:45:00Z

4

The answer is

'John' | % { $ExecutionContext.InvokeCommand.ExpandString($f) }
> John John

Credit goes to Bill_Stewart for his answer to PowerShell Double Interpolation.

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answered Apr 8, 2014 at 16:17

Tahir Hassan

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