I have a script that i'd like the user to be able to enter a string or use a file(array) that my script can cycle through.
Can this be done with a parameter?
I'd like to be able to do something like this
script.ps1 -file c:\users\joerod\desktop\listofusers.txt
or
script.ps1 -name "john doe"
Sure, but you will need to pick the default parameterset to use when a positional parameter is used since the type of both parameters is a string e.g.:
[CmdletBinding(DefaultParameterSetName="File")]
param(
[Parameter(Position=0, ParameterSetName="File")]
[string]
$File,
[Parameter(Position=0, ParameterSetName="Name")]
[string]
$Name
)
if ($psCmdlet.ParameterSetName -eq "File") {
... handle file case ...
}
else {
... must be name case ...
}
Where the DefaultParameterSetName is essential is when someone specifies this:
myscript.ps1 foo.txt
If the default parametersetname specified, PowerShell can't tell which parameterset should be used since both position 0 parameters are the same type [string]. There is no way to disambiguate which parameter to place the argument in.
Related
I need to prompt a user to enter the full path of an executable only if it cannot be found in the system PATH.
I have a parameter block like this:
[CmdletBinding()]
param (
[Parameter(Mandatory=$true)] [string]$oc_cli,
)
This determines if the executable exists in PATH:
$oc_in_path = [bool] (Get-Command "oc.exe" -ErrorAction Ignore)
I want to set the $oc_cli parameter as mandatory only if $oc_in_path is FALSE.
I have tried
$oc_in_path = [bool] (Get-Command "oc.exe" -ErrorAction Ignore)
function example-function {
param (
[Parameter(Mandatory=$oc_in_path)] [string]$oc_cli,
)
Write-Host "Do stuff"
}
example-function
which throws error Attribute argument must be a constant or a script block
I have also tried
[CmdletBinding()]
param (
if (! ( [bool] (Get-Command "oc.exe" -ErrorAction Ignore) )) {
[Parameter(Mandatory=$true)] [string]$oc_cli
}
)
How can I set the Mandatory property based on a condition?
Try the following, which relies on being able to specify default parameter values via arbitrary commands, using $(...), the subexpression operator:
[CmdletBinding()]
param (
[Parameter()] # in the absence of property values, this is optional.
[string] $oc_cli = $(
if ($cmd = Get-Command -ea Ignore oc.exe) { # oc.exe found in $env:PATH
$cmd.Path
} else { # prompt user for the location of oc.exe
do {
$userInput = Read-Host 'Specify the path of executable ''oc.exe'''
} until ($cmd = (Get-Command -ea Ignore $userInput))
$cmd.Path
}
)
)
"`$oc_cli: [$oc_cli]"
Note:
The Mandatory property of the Parameter attribute is not used, as it would - in the absence of an argument being passed - unconditionally prompt for an argument (parameter value).
The above would still accept a potentially non-existent $oc_cli argument if passed explicitly; you could use a ValidateScript attribute to prevent hat.
I have a very basic PowerShell script:
Param(
[string]$MyWord
)
function myfunc([string] $MyWord) {
Write-Host "$MyWord"
}
myfunc #PSBoundParameters
This is how I execute it:
PS C:\> .\test.ps1 -MyWord 'hello'
hello
All fine. But I want to set a default value if -MyWord isn't specified.
I tried this:
Param(
[string]$MyWord='hi'
)
function myfunc([string] $MyWord) {
Write-Host "$MyWord"
}
myfunc #PSBoundParameters
But than the output of my script was just empty. It was printing nothing when I did not describe my parameter. (it only showed 'hello' if I specified the parameter).
I also tried:
Param(
[string]$MyWord
)
function myfunc([string] $MyWord) {
[string]$MyWord='hi'
Write-Host "$MyWord"
}
myfunc #PSBoundParameters
But than the output was of course always 'hi' and never 'hello'. Even when I executed the script with the parameter -MyWord 'hello'
Can someone explaining what I'm doing wrong?
When I'm not using the function it is working as expected:
Param(
[string]$MyWord='hi'
)
Write-Host $MyWord
Output:
PS C:\> .\test.ps1 -MyWord 'hallo'
hallo
PS C:\> .\test.ps1
hi
Automatic variable $PSBoundParameters, as the name suggests, contains only bound parameters, where bound means that an actual value was supplied by the caller.
Therefore, a parameter default value does not qualify as binding the associated parameter, so $MyWord with its default value of 'hi' does not become part of $PSBoundParameters.
Note: Arguably, a parameter with a default value should also be considered bound (it is bound by its default value, as opposed to by a caller-supplied value). Either way, it would be convenient to have an automatic variable that includes default values too, so as to enable simple and comprehensive passing through of arguments. A suggestion has been submitted to the PowerShell repository as GitHub issue #3285.
Workarounds
The following solutions assume that you want to pass the default value through, and don't want to simply duplicate the default value in function myfunc (as demonstrated in Ansgar Wiecher's helpful answer), because that creates a maintenance burden.
Regarding function syntax: The following two forms are equivalent (in this case), though you may prefer the latter for consistency and readability.[1]
function myfunc([string] $MyWord = 'hi') { ... }
parameter declaration inside (...) after the function name.
function myfunc { param([string] $MyWord = 'hi') ... }
parameter declaration inside a param(...) block inside the function body.
A simple fix would be to add the default value explicitly to $PSBoundParameters:
Param(
[string]$MyWord = 'hi'
)
function myfunc ([string] $MyWord){
Write-Host "$MyWord"
}
# Add the $MyWord default value to PSBoundParameters.
# If $MyWord was actually bound, this is effectively a no-op.
$PSBoundParameters.MyWord = $MyWord
myfunc #PSBoundParameters
To achieve what you want generically, you must use reflection (introspection):
param(
[alias('foop')]
[string]$MyWord = 'hi'
)
function myfunc ([string] $MyWord) {
Write-Host "$MyWord"
}
# Add all unbound parameters that have default values.
foreach ($paramName in $MyInvocation.MyCommand.Parameters.Keys) {
if (-not $PSBoundParameters.ContainsKey($paramName)) {
$defaultVal = Get-Variable -Scope Local $paramName -ValueOnly
# A default value is identified by either being non-$null or
# by being a [switch] parameter that defaults to $true (which is bad practice).
if (-not ($null -eq $defaultVal -or ($defaultVal -is [switch] -and -not $defaultVal))) {
$PSBoundParameters[$paramName] = $defaultVal
}
}
}
myfunc #PSBoundParameters
[1] The param(...) form is required if you need to use the [CmdletBinding()] attribute with non-default values, as well as in scripts (.ps1). See this answer.
A parameter is bound only if you actually pass it a value, meaning that a parameter's default value does not show up in $PSBoundParameters. If you want to pass script parameters into a function, you must replicate the script parameter set in the function parameter set:
Param(
[string]$MyWord = 'hi'
)
function myfunc([string]$MyWord = 'hi') {
Write-Host "$MyWord"
}
myfunc #PSBoundParameters
Maintaining something like this is easier if you define both parameter sets the same way, though, so I'd put the function parameter definition in a Param() block as well:
Param(
[string]$MyWord = 'hi'
)
function myfunc {
Param(
[string]$MyWord = 'hi'
)
Write-Host "$MyWord"
}
If you want to use "Param" enclose it in the function like this:
function myfunc {
Param(
[string]$MyWord='hi'
)
Write-Host "$MyWord"
}
Very simple way is,
function myfunc([string]$MyWord = "hi") {
Write-Output $MyWord
}
I have two PowerShell scripts, which have switch parameters:
compile-tool1.ps1:
[CmdletBinding()]
param(
[switch]$VHDL2008
)
Write-Host "VHDL-2008 is enabled: $VHDL2008"
compile.ps1:
[CmdletBinding()]
param(
[switch]$VHDL2008
)
if (-not $VHDL2008)
{ compile-tool1.ps1 }
else
{ compile-tool1.ps1 -VHDL2008 }
How can I pass a switch parameter to another PowerShell script, without writing big if..then..else or case statements?
I don't want to convert the parameter $VHDL2008 of compile-tool1.ps1 to type bool, because, both scripts are front-end scripts (used by users). The latter one is a high-level wrapper for multiple compile-tool*.ps1 scripts.
You can specify $true or $false on a switch using the colon-syntax:
compile-tool1.ps1 -VHDL2008:$true
compile-tool1.ps1 -VHDL2008:$false
So just pass the actual value:
compile-tool1.ps1 -VHDL2008:$VHDL2008
Try
compile-tool1.ps1 -VHDL2008:$VHDL2008.IsPresent
Assuming you were iterating on development, it is highly likely that at some point you are going to add other switches and parameters to your main script that are going to be passed down to the next called script. Using the previous responses, you would have to go find each call and rewrite the line each time you add a parameter. In such case, you can avoid the overhead by doing the following,
.\compile-tool1.ps1 $($PSBoundParameters.GetEnumerator() | ForEach-Object {"-$($_.Key) $($_.Value)"})
The automatic variable $PSBoundParameters is a hashtable containing the parameters explicitly passed to the script.
Please note that script.ps1 -SomeSwitch is equivalent to script.ps1 -SomeSwitch $true and script.ps1 is equivalent to script.ps1 -SomeSwitch $false. Hence, including the switch set to false is equivalent to not including it.
According to a power shell team's blog (link below,) since V2 there is a technique called splatting. Basically, you use the automatic variable #PsBoundParameters to forward all the parameters. Details about splatting and the difference between # and $ are explained in the Microsoft Docs article (link below.)
Example:
parent.ps1
#Begin of parent.ps1
param(
[Switch] $MySwitch
)
Import-Module .\child.psm1
Call-Child #psBoundParameters
#End of parent.ps1
child.psm1
# Begin of child.psm1
function Call-Child {
param(
[switch] $MySwitch
)
if ($MySwitch){
Write-Output "`$MySwitch was specified"
} else {
Write-Output "`$MySwitch is missing"
}
}
#End of child.psm1
Now we can call the parent script with or without the switch
PS V:\sof\splatting> .\parent.ps1
$MySwitch is missing
PS V:\sof\splatting> .\parent.ps1 -MySwitch
$MySwitch was specified
PS V:\sof\splatting>
Update
In my original answer, I sourced the children instead of importing it as a module. It appears sourcing another script into the original just makes the parent's variables visible to all children so this will also work:
# Begin of child.ps1
function Call-Child {
if ($MySwitch){
Write-Output "`$MySwitch was specified"
} else {
Write-Output "`$MySwitch is missing"
}
}
#End of child.ps1
with
#Begin of parent.ps1
param(
[Switch] $MySwitch
)
. .\child.ps1
Call-Child # Not even specifying #psBoundParameters
#End of parent.ps1
Maybe, this is not the best way to make a program, nevertheless, this is the way it works.
About Splatting(Microsoft Docs)
How and Why to Use Splatting (passing [switch] parameters)
Another solution. If you declare your parameter with a default value of $false:
[switch] $VHDL2008 = $false
Then the following (the -VHDL2008 option with no value) will set $VHDL2008 to $true:
compile-tool1.ps1 -VHDL2008
If instead you omit the -VHDL2008 option, then this forces $VHDL2008 to use the default $false value:
compile-tool1.ps1
These examples are useful when calling a Powershell script from a bat script, as it is tricky to pass a $true/$false bool from bat to Powershell, because the bat will try to convert the bool to a string, resulting in the error:
Cannot process argument transformation on parameter 'VHDL2008'.
Cannot convert value "System.String" to type "System.Management.Automation.SwitchParameter".
Boolean parameters accept only Boolean values and numbers, such as $True, $False, 1 or 0.
In a PowerShell script, I want to read a CSV file that contains something like this:
Type Title Param1 Param2
---- ----- ------ ------
Type1 Foo type 1 ValueForType1
Type2 Foo type 2 ValueForType2
When type is Type1, I have to call a function named New-FooType1, when type is Type2, the funcation is named New-FooType2, and so on:
function New-FooType1{
param(
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Title,
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Param1
)
Write-Host "New-FooType1 $Title with $Param1"
}
function New-FooType2{
param(
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Title,
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Param2
)
Write-Host "New-FooType2 $Title with $Param2"
}
I'm trying to route the call to either of the functions, using a dynamic invocation:
$csv | % {
$cmdName = "New-Foo$($_.Type)"
Invoke-Command (gcm $cmdName) -InputObject $_
}
However, I always get an error:
Parameter set cannot be resolved using the specified named parameters
As you can see, different type mean different parameters set.
How can I solve this? I would like to avoid manipulating properties manually, because in my real life script, I have a dozen of different types, with up to 6 parameters.
Here is a complete repro sample of the issue:
$csvData = "Type;Title;Param1;Param2`nType1;Foo type 1;ValueForType1;;`nType2;Foo type 2;;ValueForType2"
$csv = ConvertFrom-csv $csvData -Delimiter ';'
$csv | ft -AutoSize
function New-FooType1{
param(
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Title,
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Param1
)
Write-Host "New-FooType1 $Title with $Param1"
}
function New-FooType2{
param(
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Title,
[Parameter(Mandatory=$true, ValueFromPipeline=$true,ValueFromPipelineByPropertyName=$true)]
[string]$Param2
)
Write-Host "New-FooType2 $Title with $Param2"
}
$csv | % {
$cmdName = "New-Foo$($_.Type)"
Invoke-Command (gcm $cmdName) -InputObject $_
}
The expected output of this script is:
New-FooType1 Foo type 1 with ValueForType1
New-FooType2 Foo type 2 with ValueForType2
Use the call operator &:
$CmdName = "New-FooType1"
$Arguments = "type1"
& $CmdName $Arguments
the call operator also supports splatting if you want the arguments bound to specific named parameters:
$Arguments = #{
"title" = "type1"
}
& $CmdName #Arguments
To invoke command by name you should use invoke operator &. Invoke-Command cmdlet support only ScriptBlock and file invocation, and file invocation only supported for remote calls.
For dynamic parameter binding you can use spatting, but in that case you have to convert PSCustomObjects, returned by ConvertFrom-Csv cmdlet, to Hashtable. You also have to strip any extra parameters from Hashtable because splatting will fail if you try to bind non-existing parameter.
Another approach for dynamic parameter binding would be to use binding from pipeline object. It looks like it is what you want to do, since you mark all your parameters with ValueFromPipelineByPropertyName option. And this approach will just ignore any extra property it can not bind to parameter. I recommend you to remove ValueFromPipeline option, because with this option in case of absence of property with parameter name PowerShell will just convert PSCustomObject to string (or to whatever type you use for parameter) and pass it as value for parameter.
So, all you need is to pass object by pipeline and use invoke operator for invocation of command with dynamic name:
$_ | & "New-Foo$($_.Type)"
dont know exactly what your trying to do, but
Invoke-Command (gcm $cmdName) ?
Try invoke-expression $cmdname
I'm writing a PowerShell script that's a wrapper to an .exe. I want to have some optional script params, and pass the rest directly to the exe. Here's a test script:
param (
[Parameter(Mandatory=$False)] [string] $a = "DefaultA"
,[parameter(ValueFromRemainingArguments=$true)][string[]]$ExeParams # must be string[] - otherwise .exe invocation will quote
)
Write-Output ("a=" + ($a) + " ExeParams:") $ExeParams
If I run with the a named param, everything is great:
C:\ > powershell /command \temp\a.ps1 -a A This-should-go-to-exeparams This-also
a=A ExeParams:
This-should-go-to-exeparams
This-also
However, if I try to omit my param, the first unnamed param is assigned to it:
C:\ > powershell /command \temp\a.ps1 This-should-go-to-exeparams This-also
a=This-should-go-to-exeparams ExeParams:
This-also
I would expect:
a=DefaultA ExeParams:
This-should-go-to-exeparams
This-also
I tried adding Position=0 to the param, but that produces the same result.
Is there a way to achieve this?
Maybe a different parameter scheme?
By default, all function parameters are positional. Windows PowerShell assigns position numbers to parameters in the order in which the parameters are declared in the function. To disable this feature, set the value of the PositionalBinding argument of the CmdletBinding attribute to $False.
have a look at How to disable positional parameter binding in PowerShell
function Test-PositionalBinding
{
[CmdletBinding(PositionalBinding=$false)]
param(
$param1,$param2
)
Write-Host param1 is: $param1
Write-Host param2 is: $param2
}
The main answer still works in version 5 (according to comments, it may have been broken for a while in version 2).
There is another option: add Position to the ValueFromRemainingArgs parameter.
Sample CommandWrapper.ps1:
param(
$namedOptional = "default",
[Parameter(ValueFromRemainingArguments = $true, Position=1)]
$cmdArgs
)
write-host "namedOptional: $namedOptional"
& cmd /c echo cmdArgs: #cmdArgs
Sample output:
>commandwrapper hello world
namedOptional: default
cmdArgs: hello world
This appears to follow from PowerShell assigning parameter positions from the first parameter with a Position designated.