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?

score 5 · Answer 1 · answered Apr 08 '14 at 16:43

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 08 '14 at 16:43

Why is the semi-colon needed in the second example? – Benjamin Hubbard Apr 08 '14 at 16:49
The semicolon is not a requirement, but it delimits the end of a command in PowerShell. – Apr 08 '14 at 17:01

score 3 · Answer 2 · edited May 23 '17 at 11:45

3

The answer is

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

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

edited May 23 '17 at 11:45

Community

answered Apr 08 '14 at 16:17

Tahir Hassan

2 Answers2