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

Question

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
)

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

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

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://docs.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

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 :).

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

To summarize and complement the existing answers, as of Windows PowerShell v5.1 / PowerShell Core 7.0.0-preview.4:

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, 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 this GitHub issue.}

---

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 official help topic as of this writing - does not work in v5.1

  • This GitHub issue asks for the documentation to be corrected and also provides a test command that shows the ineffectiveness of the workaround.

• 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.