accessing the $args array in powershell

Question

I have a test powershell V2 script that looks like this:

    function test_args()
    {
      Write-Host "here's arg 0: $args[0]"
      Write-Host "here's arg 1: $args[1]"
    }


    test_args

If I call this from the powershell command prompt I get this on the screen:

here's arg[0]: [0]

here's arg[1]: [1]

Not quite what I wanted. It seems I have to copy $args[0] and $args[1] to new variables in the script before I can use them? If I do that I can access things fine.

Is there a way to access the indexed $args in my code? I've tried using curly braces around them in various ways but no luck.

I'll be moving to named parameters eventually, but the script I'm working on (not this demo one) is a straight port of a batch file.

Ultimately, this is string-expansion (interpolation) syntax problem, as also explained in the accepted answer. In short: To embed an expression such as $args[0] - as opposed to a mere variable reference such as $var - you need $(...), the subexpression operator; ergo: "... $($args[0]) ...". For a concise summary of PowerShell's string-expansion rules, see this answer. — mklement0
– mklement0, Commented Nov 15, 2019 at 16:18

Keith Hill · Accepted Answer · 2012-09-09 18:33:10Z

66

Try this instead:

function test_args()
{
  Write-Host "here's arg 0: $($args[0])"
  Write-Host "here's arg 1: $($args[1])"
}

test_args foo bar

Note that it is $args and not $arg. Also when you use a PowerShell variable in a string, PowerShell only substitutes the variable's value. You can't directly use an expression like $args[0]. However, you can put the expression within a $() sub-expression group inside a double-quoted string to get PowerShell to evaluate the expression and then convert the result to a string.

edited Sep 9, 2012 at 18:33

answered Sep 7, 2012 at 22:28

Keith Hill

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5 Comments

larryq Over a year ago

Thank you Keith-- I changed my snippet to correct my typo when translating from my editor to SO. I guess my question is, do I need to pass $arg[0] and [1] to test_args as parameters, or will the function itself have access to the $args array?

Keith Hill Over a year ago

Functions always have access to $args. It will contain any argument that doesn't map to a defined function parameter. If there are no arguments or all the arguments map to function parameters e.g. function foo($param1, $param2){} then $args will be an empty array.

VertigoRay Over a year ago

Sometimes I have to use Out-String to get the output of a sub-expression to display as desired ... such as when working with a hashtable. Example, assumes arg 1 is a hashtable: Write-Host "here's arg 1: $($args[1] | Out-String)"

mklement0 Over a year ago

Small caveat re $args availability: Advanced functions (or scripts) - namely those whose param() block is decorated with the [CmdletBinding()] attribute and/or whose parameters are decorated with [Parameter()] attributes - fundamentally do not permit invocation unless all arguments passed bind to declared parameters. In other words: $args does not apply to advanced functions and scripts.

Timo Over a year ago

I use $args in function n{notepad $args} and call it with n argg_file. This seems PS kungfu?

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