Powershell pipe variable inside string

Question

I use

for ($i = 0; $i -le 3; $i++) {
Get-ChildItem -path $somepath|Copy-Item -Destination "c:\somefolder\$i-${$_.Name}"
}

But the destination path never translated from variables to right letters. There what I mean: assume $i = 2 and $_.name = file.exe

"c:\somefolder\$i-${$.Name}" going to c:\somefolder\2-"
"c:\somefolder\$i-$($.Name)" going to c:\somefolder\2-"
"c:\somefolder\${$.Name}$i" going to c:\somefolder\2-"
"c:\somefolder\${$.Name}" going to c:\somefolder\2-"
but "c:\somefolder\${$_.Name}" going to c:\somefolder\file.exe"

What am I doing wrong? How can I combine two variables together

Keith Hill · Accepted Answer · 2014-01-30 22:12:58Z

1

You can't access the $_ in a string like that but you can inside a scriptblock if the scriptblock is used as the argument for a parameter that accepts pipeline input e.g.:

for ($i = 0; $i -le 3; $i++) {
    Get-ChildItem $somepath | Copy-Item -Destination {"c:\somefolder\$i-$($_.Name)"} 
}

answered Jan 30, 2014 at 22:12

Keith Hill

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2 Comments

ko4evneg Over a year ago

Thanks, it worked. But can you explain why that behaviour occur?

Keith Hill Over a year ago

The $_ is typically only available within a scriptblock inside the pipeline like | Foreach {<$_ injected here>} or | Where {<$_ injected here>}. If a parameter is configured for pipeline binding (you can see this in the help on Copy-Item Destination parameter) then PowerShell allows you to use a scriptblock to determine the value for that parameter. The bonus is that PowerShell will inject $_ into that scriptblock so you can reference it there. See item 8 & 9 in this free ebook skydrive.live.com/…

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