Powershell mandatory bool always true

9
votes

I have a script that includes the following settings which returns an incorrect result if I use the mandatory parameter screen. It feels like it is failing to do some kind of type verification or casting on my input. How can I resolve it?

param ( [Parameter(Mandatory=$true)] [bool]$autoinstall )

if ( $autoinstall  ) 
{
    echo "Autoinstall true"
}
else
{
    echo "Autoinstall false"
}

This works perfectly if I call it with .\myscript.ps1 -autoinstall $false but the $autoinstall variable is always true regardless of what I pass if I use the mandatory password prompt and enter '$false'.

EDIT:

Using a switch doesn't work for me. I really need to have this be both scriptable and the mandatory parameter function for user shortcuts for on the fly use.

2
powershellparameterscasting

2 Answers

9
votes

The issue occurs because the input is interpreted as a string and you're seeing the results of PowerShell's coercion of string to bool e.g.:

59> [bool]'0'
True

60> [bool]'false'
True

61> [bool]'False'
True

62> [bool]'$false'
True

To get the "false" path to execute, just press enter when you're prompted for the parameter i.e.:

63> [bool]''
False
7
votes

Why not just use switch? Try this:

param ( [switch]$autoinstall )

if ( $autoinstall  ) 
{
    echo "Autoinstall true"
}
else
{
    echo "Autoinstall false"
}

Output:

[20:40:46] PS-ADMIN C:\Users\Graimer\Desktop> .\Untitled4.ps1
Autoinstall false
[20:42:36] PS-ADMIN C:\Users\Graimer\Desktop> .\Untitled4.ps1 -autoinstall
Autoinstall true
[20:42:38] PS-ADMIN C:\Users\Graimer\Desktop> .\Untitled4.ps1 -autoinstall:$true
Autoinstall true
[20:42:41] PS-ADMIN C:\Users\Graimer\Desktop> .\Untitled4.ps1 -autoinstall:$false
Autoinstall false