Shoot yourself in the foot with powershell

I’ve manged to shot myself in the foot in powershell twice lately, therefore I’ve figured I could write down those examples as a warning to future self (and humanity in general).

Without further ado, here they are:

Strong typing can backfire right at you

[string]$x = 'foo'
$x = ($x.ToLower() -eq 'bar')
Write-Output $x
if ($x)
{
    Write-Output "foobar"
}

Writes to console:

False
foobar

If you remove the [string] decorator, it works “sane” (prints just False).

The foot-shooting happens becuase in second line, there is an implicit cast to string, if $x is strongly typed.

The exit codes..

..are interesting, especially if you want to support PS2.0 and use negative values

Apparently, at Win7 times someone at Microsoft thought storing exit codes as unsigned int was a good idea.

PS C:\> Write-Output "exit -2" > test.ps1
PS C:\> powershell -Command '.\test.ps1'
PS C:\> echo $LASTEXITCODE
1
PS C:\> powershell -Command '.\test.ps1; exit $LASTEXITCODE'
PS C:\> echo $LASTEXITCODE
-2
PS C:\> powershell -Version 2.0 -Command '.\test.ps1; exit $LASTEXITCODE'
PS C:\> echo $LASTEXITCODE
65534

I have a strange feeling that this collection will grow bigger eventually..