PowerShell Modules and advanced functions

Question

I've written an advanced function that does stuff with the input $Text and the information coming from an Excel file. The function itself is pretty fast, only the part for reading the Excel file (Import-ExcelHC) is slow and needs some time.

This function has been made available within a module. Now every time I call this function, it needs to read the Excel file, which is normal. But the Excel file doesn't change that often, so I don't really need to read it every single time I call the function.

Is it possible to only have the Excel file read once when the module is loaded? So the function doesn't need to read the Excel file every time I call it from within a script?

I'm sorry if this seems like a noob question, but I'm new to using modules. Thank you for your help.

MyModule.PSM1:

Function Foo ($Text) {
    Begin {
        $Excel = Import-ExcelHC -File 'C\Test.xlsx' # slow part
    }
    Process {
        Write-Host "We did some stuff with $Text and $Excel"
    }
}

Thank you for your help.

Booga Roo · Accepted Answer · 2014-10-24 00:53:53Z

1

Another thought: You could also have it check the LastWriteTime property on loading the module, then in your function have it compare it to what it was when the module was loaded to make sure you're working with the latest version. This way you only reload it if it's been updated.

On module load:

$excelwritetimeonload = (Get-Childitem 'C:\Test.xlsx').lastwritetime

Then inside the function:

$excelwritetimecurrent = (Get-Childitem 'C:\Test.xlsx').lastwritetime
if ($excelwritetimecurrent -gt $excelwritetimeonload) {
    $Excel = Import-ExcelHC -File 'C:\Test.xlsx' # slow part
    }

answered Oct 24, 2014 at 0:53

Booga Roo

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1 Comment

DarkLite1 Over a year ago

Very good suggestion this one! Although, one should not forget to still do an initial call on the slow function when loading the module.

Mike Shepard · Accepted Answer · 2014-10-14 16:01:59Z

1

You can include the

$Excel = Import-ExcelHC -File 'C\Test.xlsx' # slow part

at the end of the module outside of any functions. Code outside of functions is executed when you load a module.

answered Oct 14, 2014 at 16:01

Mike Shepard

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1 Comment

DarkLite1 Over a year ago

Fully awesome! I didn't know this was possible. It's a real time saver for me :) Thank you very much Mike!

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