Working with properties of variable in if statement-CodePudding

I have coded this small script. Everything is working fine, the if-statement excluded. It doesn't matter which value the variable $status results. The if-statement results always in the else condition.

Is it quite possible to work with the properties of a Cmdlet result in an if-statement?

$filepath = "C:\Scripts\Logs"
$date = Get-Date -Format "dd.MM.yyyy HH:mm:ss"

$tapejob = Get-VBRTapeJob -Name "GFS Backup to Tape"
$tapejob | Disable-VBRJob

$status = Get-VBRTapeJob -Name "GFS Backup to Tape"

if ($status.Enabled -eq "False") 
{"$date Der Backup To Tape Job wurde erfolgreich deaktiviert." | Out-File "$filepath\DisableTapeJobLog.txt" -Append}
elseif ($status.Enabled -eq "True") 
{"$date Der Backup To Tape Job wurde nicht erfolgreich deaktiviert." | Out-File "$filepath\DisableTapeJobLog.txt" -Append}
else 
{"$date Irgendwas stimmt hier nicht. :-)" | Out-File "$filepath\DisableTapeJobLog.txt" -Append}

CodePudding user response：

Note:

In order to detect the case where $status.Enabled is not a Boolean (such as $null, if no .Enabled property exists), use the following as the first if conditional:
```
if ($status.Enabled -isnot [bool]) {
  "$date Irgendwas stimmt hier nicht. :-)" | Out-File "$filepath\DisableTapeJobLog.txt" -Append
}
```
The next section assumes that $status.Enabled returns a Boolean (bool); the complete if statement is in the bottom section.

Use ($status.Enabled -eq $false) or, preferably and more succinctly,
(-not $status.Enabled)

Generally speaking:

There is no need to compare a Boolean value against another value explicitly (see next point), but if you do, and that other value isn't already a Boolean, you need to understand how PowerShell converts it to a Boolean - see next section.
It's best to use Boolean values implicitly in conditionals; that is:
- use $someBooleanValue in lieu of $someBooleanValue -eq $true
- use -not $someBooleanValue in lieu of $someBooleanValue -eq $false
As an aside: If you already know PowerShell's to-Boolean conversion rules, you can use any value implicitly as a Boolean, simply by using it as-is in a conditional and relying on PowerShell to convert it to a Boolean; e.g.,
$val = 'nonempty string'; if ($val) { 'yes' } outputs yes, because any nonempty string is coerced to $true in a Boolean context (see below).

As for what you tried:

($status.Enabled -eq "False")

Comparing a Boolean value ($true or $false) to a string value such as "False" doesn't work as you might expect:

Due to the LHS being a Boolean, PowerShell coerces the RHS to a Boolean too before comparing, and PowerShell's to-Boolean conversion rules consider any nonempty string to be $true, irrespective of its value.

That is, [bool] "False" yields $true(!), because "False" is a nonempty string.

Therefore, your comparison is equivalent to $status.Enabled -eq [bool] "False", which is the same as $status.Enabled -eq $true(!), i.e. the opposite of your intent.

See the bottom section of this answer for a summary of PowerShell's to-Boolean conversion rules.

To put it all together:

if ($status.Enabled -isnot [bool]) {
  "$date Irgendwas stimmt hier nicht. :-)" | Out-File "$filepath\DisableTapeJobLog.txt" -Append
}
elseif (-not $status.Enabled) {
  "$date Der Backup To Tape Job wurde erfolgreich deaktiviert." | Out-File "$filepath\DisableTapeJobLog.txt" -Append
}
else {
  "$date Der Backup To Tape Job wurde nicht erfolgreich deaktiviert." | Out-File "$filepath\DisableTapeJobLog.txt" -Append
}