Having some problems getting a Start-Job script block to output to a file. The following three lines of code work without any problem:
$about_name = "C:\0\ps_about_name.txt"
$about = get-help about_* | select Name,Synopsis
if (-not (Test-
Path $about_name)) { ($about | select Name | sort Name | Out-String).replace("[Aa]bout_", "") > $about_name }
The file is created in C:\0\
But I need to do a lot of collections like this, so I naturally looked at stacking them in parallel as separate jobs. I followed online examples and so put the last line in the above as a script block invoked by Start-Job:
Start-Job { if (-not (Test-Path $about_name)) { { ($about | select Name | sort Name | Out-String).replace("[Aa]bout_", "") > $about_name } }
The Job is created, goes to status Running, and then to status Completed, but no file is created. Without Start-Job, all works, with Start-Job, nothing... I've tried a lot of variations on this but cannot get it to create the file. Can someone advise what I am doing wrong in this please?
IMO, the simplest way to get around this problem by use of the $using scope modifier.
$about_name = "C:\0\ps_about_name.txt"
$about = get-help about_* | select Name,Synopsis
$sb = { if (-not (Test-Path $using:about_name)) {
$using:about.Name -replace '^about_' | Sort-Object > $using:about_name
}
}
Start-Job -Scriptblock $sb
Explanation:
$using allows you to access local variables in a remote command. This is particularly useful when running Start-Job and Invoke-Command. The syntax is $using:localvariable.
This particular problem is a variable scope issue. Start-Job creates a background job with its own scope. When using -Scriptblock parameter, you are working within that scope. It does not know about variables defined in your current scope/session. Therefore, you must use a technique that will define the variable within the scope, pass in the variable's value, or access the local scope from the script block. You can read more about scopes at About_Scopes.
As an aside, character sets [] are not supported in the .NET .Replace() method. You need to switch to -replace to utilize those. I updated the code to perform the replace using -replace case-insensitively.
HCM's perfectly fine solution uses a technique that passes the value into the job's script block. By defining a parameter within the script block, you can pass a value into that parameter by use of -ArgumentList.
Another option is to just define your variables within the Start-Job script block.
$sb = { $about_name = "C:\0\ps_about_name.txt"
$about = get-help about_* | select Name,Synopsis
if (-not (Test-Path $about_name)) {
$about.Name -replace '^about_' | Sort-Object > $about_name
}
}
Start-Job -Scriptblock $sb
You've got to send your parameters to your job.
This does not work:
$file = "C:\temp\_mytest.txt"
start-job {"_" | out-file $file}
While this does:
$file = "C:\temp\_mytest.txt"
start-job -ArgumentList $file -scriptblock {
Param($file)
"_" | out-file $file
}
Related
I want to use start-job to run a .ps1 script requiring a parameter. Here's the script file:
#Test-Job.ps1
Param (
[Parameter(Mandatory=$True)][String]$input
)
$output = "$input to output"
return $output
and here is how I am running it:
$input = "input"
Start-Job -FilePath 'C:\PowerShell\test_job.ps1' -ArgumentList $input -Name "TestJob"
Get-Job -name "TestJob" | Wait-Job | Receive-Job
Get-Job -name "TestJob" | Remove-Job
Run like this, it returns " to output", so $input is null in the script run by the job.
I've seen other questions similar to this, but they mostly use -Scriptblock in place of -FilePath. Is there a different method for passing parameters to files through Start-Job?
tl;dr
$input is an automatic variable (value supplied by PowerShell) and shouldn't be used as a custom variable.
Simply renaming $input to, say, $InputObject solves your problem.
As Lee_Dailey notes, $input is an automatic variable and shouldn't be assigned to (it is automatically managed by PowerShell to provide an enumerator of pipeline input in non-advanced scripts and functions).
Regrettably and unexpectedly, several automatic variables, including $input, can be assigned to: see this answer.
$input is a particularly insidious example, because if you use it as a parameter variable, any value you pass to it is quietly discarded, because in the context of a function or script $input invariably is an enumerator for any pipeline input.
Here's a simple example to demonstrate the problem:
PS> & { param($input) "[$input]" } 'hi'
# !! No output - the argument was quietly discarded.
That the built-in definition of $input takes precedence can be demonstrated as follows:
PS> 'ho' | & { param($input) "[$input]" } 'hi'
ho # !! pipeline input took precedence
While you can technically get away with using $input as a regular variable (rather than a parameter variable) as long as you don't cross scope boundaries, custom use of $input should still be avoided:
& {
$input = 'foo' # TO BE AVOIDED
"[$input]" # Technically works: -> '[foo]'
& { "[$input]" } # FAILS, due to child scope: -> '[]'
}
Is there any command to list all functions I've created in a script?
Like i created function doXY and function getABC or something like this.
Then I type in the command and it shows:
Function doXY
Function getABC
Would be a cool feature^^
Thanks for all your help.
You can have PowerShell parse your script, and then locate the function definitions in the resulting Abstract Syntax Tree (AST).
Get-Command is probably the easiest way to access the AST:
# Use Get-Command to parse the script
$myScript = Get-Command .\path\to\script.ps1
$scriptAST = $myScript.ScriptBlock.AST
# Search the AST for function definitions
$functionDefinitions = $scriptAST.FindAll({
$args[0] -is [Management.Automation.Language.FunctionDefinitionAst]
}, $false)
# Report function name and line number in the script
$functionDefinitions |ForEach-Object {
Write-Host "Function '$($_.Name)' found on line $($_.StartLineNumber)!"
}
You can also use this to analyze the functions' contents and parameters if necessary.
Where your script is named things.ps1, something like...
cat ./things.ps1 | grep function
For MacOS/Linux or...
cat ./things.ps1 | select-string function
For Windows.
This is a built-in feature as shown in the PowerShell help files.
About_Providers
Similar questions have been asked before. So, this is a potential duplicate of:
How to get a list of custom Powershell functions?
Answers... Using the PSDrive feature
# To get a list of available functions
Get-ChildItem function:\
# To remove a powershell function
# removes `someFunction`
Remove-Item function:\someFunction
Or
Function Get-MyCommands {
Get-Content -Path $profile | Select-String -Pattern "^function.+" | ForEach-Object {
[Regex]::Matches($_, "^function ([a-z.-]+)","IgnoreCase").Groups[1].Value
} | Where-Object { $_ -ine "prompt" } | Sort-Object
}
Or this one
Get List Of Functions From Script
$currentFunctions = Get-ChildItem function:
# dot source your script to load it to the current runspace
. "C:\someScript.ps1"
$scriptFunctions = Get-ChildItem function: | Where-Object { $currentFunctions -notcontains $_ }
$scriptFunctions | ForEach-Object {
& $_.ScriptBlock
}
As for this...
Thanks, this is kind of what i want, but it also shows functions like
A:, B:, Get-Verb, Clear-Host, ...
That is by design. If you want it another way, then you have to code that.
To get name of functions in any script, it has to be loaded into memory first, then you can dot source the definition and get the internals. If you just want the function names, you can use regex to get them.
Or as simple as this...
Function Show-ScriptFunctions
{
[cmdletbinding()]
[Alias('ssf')]
Param
(
[string]$FullPathToScriptFile
)
(Get-Content -Path $FullPathToScriptFile) |
Select-String -Pattern 'function'
}
ssf -FullPathToScriptFile 'D:\Scripts\Format-NumericRange.ps1'
# Results
<#
function Format-NumericRange
function Flush-NumberBuffer
#>
This function will parse all the functions included in a .ps1 file, and then will return objects for each function found.
The output can be piped directly into Invoke-Expression to load the retuned functions into the current scope.
You can also provide an array of desired names, or a Regular Expression to constrain the results.
My use case was I needed a way for loading individual functions from larger scripts, that I don't own, so I could do pester testing.
Note: only tested in PowerShell 7, but I suspect it will work in older versions too.
function Get-Function {
<#
.SYNOPSIS
Returns a named function from a .ps1 file without executing the file
.DESCRIPTION
This is useful where you have a blended file containing functions and executed instructions.
If neither -Names nor -Regex are provided then all functions in the file are returned.
Returned objects can be piped directly into Invoke-Expression which will place them into the current scope.
Returns an array of objects with the following
- .ToString()
- .Name
- .Parameters
- .Body
- .Extent
- .IsFilter
- .IsWorkFlow
- .Parent
.PARAMETER -Names
Array of Strings; Optional
If provided then function objects of these names will be returned
The name must exactly match the provided value
Case Insensitive.
.PARAMETER -Regex
Regular Expression; Optional
If provided then function objects with names that match will be returned
Case Insensitive
.EXAMPLE
Get all the functions names included in the file
Get-Function -name TestA | select name
.EXAMPLE
Import a function into the current scope
Get-Function -name TestA | Invoke-Expression
#>
param (
$File = "c:\fullpath\SomePowerShellScriptFile.ps1"
,
[alias("Name", "FunctionNames", "Functions")]
$Names
,
[alias("NameRegex")]
$Regex
) # end function
# get the script and parse it
$Script = Get-Command /Users/royomi/Documents/dev/javascript/BenderBot_AI/Import-Function.ps1
$AllFunctions = $Script.ScriptBlock.AST.FindAll({$args[0] -is [Management.Automation.Language.FunctionDefinitionAst]}, $false)
# return all requested functions
$AllFunctions | Where-Object { `
( $Names -and $Names -icontains $_.Name ) `
-or ( $Regex -and $Names -imatch $Regex ) `
-or (-not $Names -and -not $Regex) `
} # end where-object
} # end function Get-Function
Is there any way to run parallel programmed functions in PowerShell?
Something like:
Function BuildParallel($configuration)
{
$buildJob = {
param($configuration)
Write-Host "Building with configuration $configuration."
RunBuilder $configuration;
}
$unitJob = {
param()
Write-Host "Running unit."
RunUnitTests;
}
Start-Job $buildJob -ArgumentList $configuration
Start-Job $unitJob
While (Get-Job -State "Running")
{
Start-Sleep 1
}
Get-Job | Receive-Job
Get-Job | Remove-Job
}
Does not work because it complains about not recognizing "RunUnitTests" and "RunBuilder", which are functions declared in the same script file. Apparently this happens because the script block is a new context and does not know anything about the scripts declared in the same file.
I could try to use -InitializationScript in Start-Job, but both RunUnitTests and RunBuilder call more functions declared in the same file or referred from other files, so...
I'm sure there's a way to do this, since it's just modular programming (functions, routines and all that stuff).
You could have the functions in a separate file and import them into the current context wherever needed via dot sourcing. I do this in my Powershell profile, so some of my custom functions are available.
$items = Get-ChildItem "$PSprofilePath\functions"
$items | ForEach-Object {
. $_.FullName
}
If you wanted import one file, it would just be:
. C:\some\path\RunUnitTests.ps1
I'm creating a dynamic ScriptBlock the way below so I can use local functions and variables and easily pass them to remote computers via Invoke-Command. The issue is that since all the text inside Create is enclosed with double quotes, I loose all my syntax highlighting since all editors see the code as one big string.
While this is only a cosmetic issue, I'd like to find a work around that allow my code to be passed without having double quotes. I've tried passing a variable inside Create instead of the actually text, but it does not get interpreted.
function local_admin($a, $b) {
([adsi]"WinNT://localhost/Administrators,group").Add("WinNT://$a/$b,user")
}
$SB = [ScriptBlock]::Create(#"
#Define Function
function local_admin {$Function:local_admin}
local_admin domain username
"#)
Invoke-Command -ComputerName server2 -ScriptBlock $SB
You can pass the function into the remote session using the following example. This allows you to define the ScriptBlock using curly braces instead of as a string.
# Define the function
function foo {
"bar";
}
$sb = {
# Import the function definition into the remote session
[void](New-Item -Path $args[0].PSPath -Value $args[0].Definition);
# Call the function
foo;
};
#(gi function:foo) | select *
Invoke-Command -ComputerName . -ScriptBlock $sb -ArgumentList (Get-Item -Path function:foo);
Here is a modified version of your function. Please take note that the domain and username can be dynamically passed into the remote ScriptBlock using the -ArgumentList parameter. I am using the $args automatic variable to pass objects into the ScriptBlock.
function local_admin($a, $b) {
([adsi]"WinNT://localhost/Administrators,group").Add("WinNT://$a/$b,user")
}
$SB = {
#Define Function
[void](New-Item -Path $args[0].PSPath -Value $args[0].Definition);
# Call the function
local_admin $args[1] $args[2];
}
Invoke-Command -ComputerName server2 -ScriptBlock $SB -ArgumentList (Get-Item -Path function:local_admin), 'domain', 'username';
I have a problem with the Get-Process command in Powershell, when i use it inside a Job.
I would like to get a process by PID, so i am doing the below:
$MyProcess = Get-Process | Where-Object { $_.Id -eq $parentProcessID }
The above, when it is called as a command from a Powershell script, returns me the process expected.
If I use the exact same command inside a Start-Job{} block then it gives me null, even for a process that is running. For example:
Start-Job {
$parentProcessID = $args
$MyProcess = Get-Process | Where-Object { $_.Id -eq $parentProcessID }
if($MyProcess -eq $null)
{
echo "Nothing returned"
}
} -ArgumentList "$parentProcessID"
Is there anything i am missing here? Has anyone run into similar situation before?
Any insights appreciated.
Thanks.
$args is an array, if you still want to use make sure to pick its first element:
$parentProcessID = $args[0]
Also, Get-Process has an Id parameter, there's no need to use the Where-Object cmdlet:
Get-Process -Id $parentProcessID
Another avantage of the Id parameter is that it takes an array of Id's so it would have work if you passes to it the value of $args as is.
You can also use names parameters for the scriptblock instaed of using $args:
Start-Job {
param([int[]]$procid)
$MyProcess = Get-Process -Id $procid
(...)