How to pass boolean values to a PowerShell script from a command prompt

Question

I have to invoke a PowerShell script from a batch file. One of the arguments to the script is a boolean value:

C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -NoProfile -File .\RunScript.ps1 -Turn 1 -Unify $false

The command fails with the following error:

Cannot process argument transformation on parameter 'Unify'. Cannot convert value "System.String" to type "System.Boolean", parameters of this type only accept booleans or numbers, use $true, $false, 1 or 0 instead.

At line:0 char:1
+  <<<< <br/>
+ CategoryInfo          : InvalidData: (:) [RunScript.ps1], ParentContainsErrorRecordException <br/>
+ FullyQualifiedErrorId : ParameterArgumentTransformationError,RunScript.ps1

As of now I am using a string to boolean conversion inside my script. But how can I pass boolean arguments to PowerShell?

Scudder

Answer 1

It appears that powershell.exe does not fully evaluate script arguments when the -File parameter is used. In particular, the $false argument is being treated as a string value, in a similar way to the example below:

PS> function f( [bool]$b ) { $b }; f -b '$false'
f : Cannot process argument transformation on parameter 'b'. Cannot convert value 
"System.String" to type "System.Boolean", parameters of this type only accept 
booleans or numbers, use $true, $false, 1 or 0 instead.
At line:1 char:36
+ function f( [bool]$b ) { $b }; f -b <<<<  '$false'
    + CategoryInfo          : InvalidData: (:) [f], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : ParameterArgumentTransformationError,f

Instead of using -File you could try -Command, which will evaluate the call as script:

CMD> powershell.exe -NoProfile -Command .\RunScript.ps1 -Turn 1 -Unify $false
Turn: 1
Unify: False

As David suggests, using a switch argument would also be more idiomatic, simplifying the call by removing the need to pass a boolean value explicitly:

CMD> powershell.exe -NoProfile -File .\RunScript.ps1 -Turn 1 -Unify
Turn: 1
Unify: True

Silvia

For those (like me) who have to keep the "-File" parameter, and can't change to a switch argument, but do have control over the string values that are sent, then the simplest solution is to convert the parameter to a boolean using [System.Convert]::ToBoolean($Unify); the string values must then be "True" or "False". – Napolitano

In order for [System.Convert]::ToBoolean($Unify) to evaluate to true, $Unify must -eq "true" or "True". Otherwise, [System.Convert]::ToBoolean($Unify) evaluates to false. – Belva

Answer 2

A more clear usage might be to use switch parameters instead. Then, just the existence of the Unify parameter would mean it was set.

Like so:

param (
  [int] $Turn,
  [switch] $Unify
)

Mummer

This should be the accepted answer. To further the discussion, you can set a default value like any other parameter like so: [switch] $Unify = $false – Allene

I overlooked this answer, as I was sure Boolean was the way to go. It is not. Switch encapsulates the functionality of the boolean, and stops these kind of errors: " Cannot convert value "False" to type "System.Management.Automation.ParameterAttribute". Switches worked for me. – Neral

@MarioTacke If you don't specify the switch parameter when invoking the script then it is automatically set to $false. So there's no need to explicitly set a default value. – Persian

This suggestion worked very well; was able to update one of the params from [bool] to [switch] and this successfully allowed me to pass the argument via Task Scheduler. – Parch

If you are using the [Parameter] attribute on any of the parameters, you have to make sure that you pass the switch parameters as switches and not as booleans. So e.g. -Unify for true and nothing for false. Otherwise -Unify $false or -Unify $true would raise error "A positional parameter cannot be found that accepts argument '$true'" – Expostulation

Answer 3

This is an older question, but there is actually an answer to this in the PowerShell documentation. I had the same problem, and for once RTFM actually solved it. Almost.

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_powershell_exe

Documentation for the -File parameter states that "In rare cases, you might need to provide a Boolean value for a switch parameter. To provide a Boolean value for a switch parameter in the value of the File parameter, enclose the parameter name and value in curly braces, such as the following: -File .\Get-Script.ps1 {-All:$False}"

I had to write it like this:

PowerShell.Exe -File MyFile.ps1 {-SomeBoolParameter:False}

So no '$' before the true/false statement, and that worked for me, on PowerShell 4.0

Eighteenmo

Thank you for sharing! Solved my problem perfectly. – Michelsen

The link in the answer seems to have had its content changed. However, I found the answer here – Abortionist

Current documentation link about_powershell.exe alternatively just rung powershell -h. – Maurey

I'm surprised that this awkward workaround ever worked - it doesn't in Windows PowerShell v5.1 (neither with nor without a leading $); also note that it is no longer necessary in PowerShell Core. I've asked for the documentation to be corrected; see github.com/MicrosoftDocs/PowerShell-Docs/issues/4964 – Quint

Answer 4

Try setting the type of your parameter to [bool]:

param
(
    [int]$Turn = 0
    [bool]$Unity = $false
)

switch ($Unity)
{
    $true { "That was true."; break }
    default { "Whatever it was, it wasn't true."; break }
}

This example defaults $Unity to $false if no input is provided.

Usage

.\RunScript.ps1 -Turn 1 -Unity $false

Educt

Emperor XLII's answer and your comment on it regarding the -File parameter should cover every aspect of the original question. I'll leave my answer because someone may also find my hint on providing a default value useful. – Educt

Well done Filburt. Your answer caused me to check my script, which already has default specified as the required value $false (I wrote that several years ago and had forgotten all about it) - so I don't even have to specify the problematic boolean parameter on the command line now. Excellent :) – Alinaaline

Answer 5

I think, best way to use/set boolean value as parameter is to use in your PS script it like this:

Param(
    [Parameter(Mandatory=$false)][ValidateSet("true", "false")][string]$deployApp="false"   
)

$deployAppBool = $false
switch($deployPmCmParse.ToLower()) {
    "true" { $deployAppBool = $true }
    default { $deployAppBool = $false }
}

So now you can use it like this:

.\myApp.ps1 -deployAppBool True
.\myApp.ps1 -deployAppBool TRUE
.\myApp.ps1 -deployAppBool true
.\myApp.ps1 -deployAppBool "true"
.\myApp.ps1 -deployAppBool false
#and etc...

So in arguments from cmd you can pass boolean value as simple string :).

Keitt

Answer 6

Running powershell scripts on linux from bash gives the same problem. Solved it almost the same as LarsWA's answer:

Working:

pwsh -f ./test.ps1 -bool:true

Not working:

pwsh -f ./test.ps1 -bool=1
pwsh -f ./test.ps1 -bool=true
pwsh -f ./test.ps1 -bool true
pwsh -f ./test.ps1 {-bool=true}
pwsh -f ./test.ps1 -bool=$true
pwsh -f ./test.ps1 -bool=\$true
pwsh -f ./test.ps1 -bool 1
pwsh -f ./test.ps1 -bool:1

Discussion

same situation here. This is dumb. – Harshman

oh no it was just one : i missedd – Richmond

Answer 7

To summarize and complement the existing answers, as of Windows PowerShell v5.1 (the latest and last version) / PowerShell (Core) 7.3.3:

David Mohundro's answer rightfully points that instead of [bool] parameters you should use [switch] parameters in PowerShell, where the presence vs. absence of the switch name (-Unify specified vs. not specified) implies its value, which makes the original problem go away.

---

However, on occasion you may still need to pass the switch value explicitly, particularly if you're constructing a command line programmatically:

---

In PowerShell Core 7+, the original problem (described in Emperor XLII's answer) has been fixed.

That is, to pass $true explicitly to a [switch] parameter named -Unify you can now write:

pwsh -File .\RunScript.ps1 -Unify:$true  # !! ":" separates name and value, no space

The following values can be used: $false, false, $true, true, but note that passing 0 or 1 does not work.

Note how the switch name is separated from the value with : and there must be no whitespace between the two.

^{Note: If you declare a [bool] parameter instead of a [switch] (which you generally shouldn't), you must use the same syntax. Even though -Unify $false should work, it currently doesn't - see GitHub issue #10838.}

---

In Windows PowerShell, the original problem persists, and - given that Windows PowerShell is no longer actively developed - is unlikely to get fixed.

• The workaround suggested in LarsWA's answer - even though it is based on the since corrected official help topic as of this writing - does not work in v5.1

• Using -Command instead of -File is the only effective workaround:

:: # From cmd.exe
powershell -Command "& .\RunScript.ps1 -Unify:$true" 

With -Command you're effectively passing a piece of PowerShell code, which is then evaluated as usual - and inside PowerShell passing $true and $false works (but not true and false, as now also accepted with -File).

Caveats:

• Using -Command can result in additional interpretation of your arguments, such as if they contain $ chars. (with -File, arguments are literals).

• Using -Command can result in a different exit code.

For details, see this answer and this answer.

Quint

The most complete answer. This one should be marked as an answer here – Lyudmila

I appreciate the sentiment, @Kamarey. It's unlikely that the OP will come back and change what answer is the accepted one, but up-voting this one (which I assume you have done, thank you) will help it become more visible. – Quint

Answer 8

In PowerShell, boolean parameters can be declared by mentioning their type before their variable.

    function GetWeb() {
             param([bool] $includeTags)
    ........
    ........
    }

You can assign value by passing $true | $false

    GetWeb -includeTags $true

Laundromat

Just passing the named input arguments explicitly like that worked a treat. Thanks Ahmed – Wetzell

The question is about calling the PowerShell CLI (powershell.exe) from cmd.exe, invoking a script that already has as [bool] parameter defined. You're answering an unrelated question. – Quint

Answer 9

I had something similar when passing a script to a function with invoke-command. I ran the command in single quotes instead of double quotes, because it then becomes a string literal. 'Set-Mailbox $sourceUser -LitigationHoldEnabled $false -ElcProcessingDisabled $true';

Illa

Answer 10

Based on my test, a default value specification does not work for a parameter that is expected to be a boolean in the Function.

You can use the [switch] type or if you really want to use boolean, you should specify default value at the start of the function like below:

Function nullRules {
    Param
    (
         [Parameter(Mandatory=$false)] $boolWins

    )
   if ([DBNull]::Value.Equals($boolWins)) {$boolWins=$false}
   ....
   ....
}

Tache

Based on mt testing, ([DBNull]::Value.Equals($boolWins)) returns $false whether a value is passed to $boolWins or not. Therefore, the call to set $boolWins to $false if $boolWins is $null is superfluous. If $boolWins is omitted then a default boolean value of $false is automatically assigned. – Rosenda

Answer 11

You can also use 0 for False or 1 for True. It actually suggests that in the error message:

Cannot process argument transformation on parameter 'Unify'. Cannot convert value "System.String" to type "System.Boolean", parameters of this type only accept booleans or numbers, use $true, $false, 1 or 0 instead.

For more info, check out this MSDN article on Boolean Values and Operators.

Blaubok

That does not work. It is expecting integer number 1 or 0, but passing it through -File interprets it as string, thus fails with same error. – Isola

This answer is wrong, as the suggestion doesn't work – Hughie