Positional parameter cannot be found

Question

I'm not sure why I'm getting the following error

Copy-Item : A positional parameter cannot be found that accepts argument 'C:\Code\PS\Auths\2.jpg'. At C:\Code\PS\auth-grab.ps1:9 char:12

C:\Code\PS\Auths\2.jpg is the correct path.

(I'm getting one of these for each of the items in the pipeline)

When I echo $rv I get the correct pathand $_ should be right. Where am I going wrong?

oops script below :

function Generate-FileName($fi)
{           
    $rv = "C:\Code\PS\New\"+ $fi.Name
    #echo rv    
}

Get-ChildItem Auths\*.* -include 1.jpg, 2.jpg | 
ForEach-Object {        
    Copy-Item $_ -destination Generate-FileName(Get-ChildItem $_)       
}

Note if i echo $rv I get the path I want

Isn't it some problem with spaces in file names or in your parameters? — jumbo
– jumbo, Commented Jun 11, 2012 at 14:32
Have you tried echoing out $_ ...whilst you're about it write-host $_.fullname and $_.name just to be sure you're working with the correct path? — nimizen
– nimizen, Commented Jun 11, 2012 at 14:42

Angshuman Agarwal · Accepted Answer · 2012-06-11 20:03:01Z

3

Wrap the function - Generate-FileName in brackets like this -

ForEach-Object {        
    Copy-Item $_ -destination (Generate-FileName(Get-ChildItem $_))      
}

Enclosing it in parenthesis forces the expression.

OR

Copy the return value of the function in a variable and use the variable in the Copy-Item as below -

function Generate-FileName($fi)
{           
    "C:\Code\PS\New\"+ $fi.Name
}

Get-ChildItem Auths\*.* -include 1.jpg, 2.jpg | 
ForEach-Object {   
    $destination =  Generate-FileName(Get-ChildItem $_)           
    Copy-Item $_ -destination $destination
}

edited Jun 11, 2012 at 20:03

answered Jun 11, 2012 at 14:56

Angshuman Agarwal

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4 Comments

Angshuman Agarwal Over a year ago

You might not want to keep $rv at all. Just have this & try [I have not tried this part] - "C:\Code\PS\New\"+ $fi.Name

Johnno Nolan Over a year ago

the only reason I had $rv was to echo it.

Angshuman Agarwal Over a year ago

yeah, I guess for debugging the value. But, in production script, you might not need it. Thats what I meant.

Johnno Nolan Over a year ago

yeah removing $rv and not returning it works. e.g. function Generate-FileName($fi) { "C:\Code\PS\New\"+ $fi.Name }

jumbo · Accepted Answer · 2012-06-11 15:31:22Z

0

I think your function Generate-FileName doesn't return anything.

I think your script generate this line with copy-item:

Copy-Item C:\Code\PS\Auths\2.jpg -destination

Try it like this:

function Generate-FileName($fi)
{           
    $rv = "C:\Code\PS\New\"+ $fi.Name
    return $rv # here is the change
}

answered Jun 11, 2012 at 15:31

jumbo

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6 Comments

Angshuman Agarwal Over a year ago

I don't think so. It is the problem with function evaluation only. I tried the same sample in Powershell ISE.

jumbo Over a year ago

@AngshumanAgarwal I think that I found the right solution. You added returning in your last edit and that was what I suggested (firstly in comments) and that was what solved the problem...

Angshuman Agarwal Over a year ago

You may try what you are saying without modifying anything else except what you have suggested and run full code from John in ISE. Additionally, you may read John's comments too - yeah removing $rv and not returning it works. e.g. function Generate-FileName($fi) {"C:\Code\PS\New\"+ $fi.Name } Its not only returning. Its the way you call the function too. Moreover, $rv is not required. That was just for debugging purpose.

jumbo Over a year ago

Ok. I get it. But I have a question: What is difference between function Generate-FileName($fi) {"C:\Code\PS\New\"+ $fi.Name } and function Generate-FileName($fi) {$rv = "C:\Code\PS\New\"+ $fi.Name; return $rv } ?

Angshuman Agarwal Over a year ago

We don’t need to use the return keyword like we do in C style function. Whatever expressions and statements that have output will contribute to the output of our function. So, above we just want the output of "C:\Code\PS\New\"+ $fi.Name. For more in-depth understanding read here - rkeithhill.wordpress.com/2007/09/16/… under the heading called - Function Output Consists of Everything That Isn’t Captured

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