With my following code seems Write-Host puts out variables in a strange way (for me coming from C# at least).
Code is here
function Run(
[string] $command,
[string] $args
)
{
Write-Host 'from function - command is:' $command '.args is: ' $args
}
$cmd = "ping"
$args = "208.67.222.222"
Write-Host 'from main - command is:' $cmd '.args is: ' $args
Run("ping","208.67.222.222")
Output is here
from main - command is: ping .args is: 208.67.222.222
from function - command is: ping 208.67.222.222 .args is:
How come Write-Host from main works as I expect, but within the function it outputs all variables at the same time? How can I correct this behaviour?
$args in the function is an automatic variable. It is an array that contains all the arguments passed to the function.
Use something besides $args for your IP address variable.
Related
I'm trying to send just the result I want from a called PowerShell script back to the calling script.
So the script testcaller.ps1
$Result = Invoke-Expression "$PSScriptRoot\testcalled"
$LogMessage = "TestCalled ended with Result $Result"
Write-Output $LogMessage
Calls the script testcalled.ps1
$TestMessage = "this is a test"
Write-Output $TestMessage
$Level = 1
exit $Level
When run it produces this...
TestCalled ended with Result this is a test
0
I have two problems. I get the testmessage passed back to my calling script and the level past back is 0 when it should be 1. What I want to see is...
TestCalled ended with Result 1
Given testcalled.ps1
'hello world'
function Say-Hello { 'hello!' }
exit 1
If you want to run this external script from another script you can either dot source it:
The functions, variables, aliases, and drives
that the script creates are created in the scope in which you are
working. After the script runs, you can use the created items and
access their values in your session.
$Result = . "$PSScriptRoot\testcalled.ps1"
$Result # => hello world
Say-Hello # => 'hello!'
$LASTEXITCODE # => 1
Or use the call operator &:
The call operator executes in a child scope.
Meaning that, functions, variables, aliases, and drives will not be available on the current scope.
$Result = & "$PSScriptRoot\testcalled.ps1"
$Result # => hello world
Say-Hello # => SayHello: The term 'SayHello' is not recognized as a name of a cmdlet, function....
$LASTEXITCODE # => 1
As you can see, on both cases, you can use the automatic variable $LASTEXITCODE.
Last, but not least, it is not recommended to use Invoke-Expression. See https://devblogs.microsoft.com/powershell/invoke-expression-considered-harmful/
I am porting a script from bash to PowerShell, and I would like to keep the same support for argument parsing in both. In the bash, one of the possible arguments is -- and I want to also detect that argument in PowerShell. However, nothing I've tried so far has worked. I cannot define it as an argument like param($-) as that causes a compile error. Also, if I decide to completely forego PowerShell argument processing, and just use $args everything appears good, but when I run the function, the -- argument is missing.
Function Test-Function {
Write-Host $args
}
Test-Function -- -args go -here # Prints "-args go -here"
I know about $PSBoundParameters as well, but the value isn't there, because I can't bind a parameter named $-. Are there any other mechanisms here that I can try, or any solution?
For a bit more context, note that me using PowerShell is a side effect. This isn't expected to be used as a normal PowerShell command, I have also written a batch wrapper around this, but the logic of the wrapper is more complex than I wanted to write in batch, so the batch wrapper just calls the PowerShell function, which then does the more complex processing.
I found a way to do so, but instead of double-hyphen you have to pass 3 of them.
This is a simple function, you can change the code as you want:
function Test-Hyphen {
param(
${-}
)
if (${-}) {
write-host "You used triple-hyphen"
} else {
write-host "You didn't use triple-hyphen"
}
}
Sample 1
Test-Hyphen
Output
You didn't use triple-hyphen
Sample 2
Test-Hyphen ---
Output
You used triple-hyphen
As an aside: PowerShell allows a surprising range of variable names, but you have to enclose them in {...} in order for them to be recognized; that is, ${-} technically works, but it doesn't solve your problem.
The challenge is that PowerShell quietly strips -- from the list of arguments - and the only way to preserve that token is you precede it with the PSv3+ stop-parsing symbol, --%, which, however, fundamentally changes how the arguments are passed and is obviously an extra requirement, which is what you're trying to avoid.
Your best bet is to try - suboptimal - workarounds:
Option A: In your batch-file wrapper, translate -- to a special argument that PowerShell does preserve and pass it instead; the PowerShell script will then have to re-translate that special argument to --.
Option B: Perform custom argument parsing in PowerShell:
You can analyze $MyInvocation.Line, which contains the raw command line that invoked your script, and look for the presence of -- there.
Getting this right and making it robust is nontrivial, however.
Here's a reasonably robust approach:
# Don't use `param()` or `$args` - instead, do your own argument parsing:
# Extract the argument list from the invocation command line.
$argList = ($MyInvocation.Line -replace ('^.*' + [regex]::Escape($MyInvocation.InvocationName)) -split '[;|]')[0].Trim()
# Use Invoke-Expression with a Write-Output call to parse the raw argument list,
# performing evaluation and splitting it into an array:
$customArgs = if ($argList) { #(Invoke-Expression "Write-Output -- $argList") } else { #() }
# Print the resulting arguments array for verification:
$i = 0
$customArgs | % { "Arg #$((++$i)): [$_]" }
Note:
There are undoubtedly edge cases where the argument list may not be correctly extracted or where the re-evaluation of the raw arguments causes side effect, but for the majority of cases - especially when called from outside PowerShell - this should do.
While useful here, Invoke-Expression should generally be avoided.
If your script is named foo.ps1 and you invoked it as ./foo.ps1 -- -args go -here, you'd see the following output:
Arg #1: [--]
Arg #2: [-args]
Arg #3: [go]
Arg #4: [-here]
I came up with the following solution, which works well also inside pipelines multi-line expressions. I am using the PowerShell Parser to parse the invocation expression string (while ignoring any incomplete tokens, which might be present at the end of $MyInfocation.Line value) and then Invoke-Expression with Write-Output to get the actual argument values:
# Parse the whole invocation line
$code = [System.Management.Automation.Language.Parser]::ParseInput($MyInvocation.Line.Substring($MyInvocation.OffsetInLine - 1), [ref]$null, [ref]$null)
# Find our invocation expression without redirections
$myline = $code.Find({$args[0].CommandElements}, $true).CommandElements | % { $_.ToString() } | Join-String -Separator ' '
# Get the argument values
$command, $arguments = Invoke-Expression ('Write-Output -- ' + $myline)
# Fine-tune arguments to be always an array
if ( $arguments -is [string] ) { $arguments = #($arguments) }
if ( $arguments -eq $null ) { $arguments = #() }
Please be aware that the original values in the function call are reevaluated in Invoke-Expression, so any local variables might shadow values of the actual arguments. Because of that, you can also use this (almost) one-liner at the top of your function, which prevents the pollution of local variables:
# Parse arguments
$command, $arguments = Invoke-Expression ('Write-Output -- ' + ([System.Management.Automation.Language.Parser]::ParseInput($MyInvocation.Line.Substring($MyInvocation.OffsetInLine - 1), [ref]$null, [ref]$null).Find({$args[0].CommandElements}, $true).CommandElements | % { $_.ToString() } | Join-String -Separator ' '))
# Fine-tune arguments to be always an array
if ( $arguments -is [string] ) { $arguments = #($arguments) }
if ( $arguments -eq $null ) { $arguments = #() }
I have a script tester.ps1; the first thing it does is call a function (defined within the script itself) called main.
I need to pass in the automatic variable $args that was passed into it from the commandline.
How do I do this?
The following doesn't seem to work:
#Requires -Version 5.0
#scriptname: tester.ps1
function main($args) {
Write-Host $args
}
# Entry point
main $args
When I save this tester.ps1 and call it, the function doesn't see the passed-in parameter?
PS> . .\tester.ps1 hello world
From entry point: hello world
From Function:
In your example, simply removing $args from the main function declaration, would be enough to have the output you want.
Though, be aware that if you want to pass parameters by name, you need to call main with the splatting operator #, for example:
#Requires -Version 5.0
#scriptname: tester.ps1
function main($myString, $otherVar) {
Write-Host $myString
}
# Entry point
Write-Host "Not using splatting: " -NoNewline
main $args
Write-Host "Using splatting: " -NoNewline
main #args
Output:
PS> . .\test.ps1 -myString "Hi World" -otherVar foobar
Not using splatting: -myString Hi World -otherVar foobar
Using splatting: Hi World
Find more about the splatting operator # here
Based on Jeroen Mostert's comment*; the solution is below.
Basically I was incorrectly trying to 'overload' or 'shadow' the built-in $arg variable.
I just need to have a param with a different name like this:
#Requires -Version 5.0
function main($my_args) {
write-host "From Function:" $my_args
}
# Entry point
write-host "From entry point:" $args
main $args
> . .\tester.ps1 hello world
From entry point: hello world
From Function: hello world
This question already has an answer here:
Parenthesis Powershell functions
(1 answer)
Closed 7 years ago.
I've been toying around with this dang parameter passing to powershell jobs.
I need to get two variables in the script calling the job, into the job. First I tried using -ArgumentList, and then using $args[0] and $args[1] in the -ScriptBlock that I provided.
function Job-Test([string]$foo, [string]$bar){
Start-Job -ScriptBlock {#need to use the two args in here
} -Name "Test" -ArgumentList $foo, $bar
}
However I realized that -ArgumentList gives these as parameters to -FilePath, so I moved the code in the scriptblock into its own script that required two parameters, and then pointed -FilePath at this script.
function Job-Test([string]$foo, [string]$bar){
$myArray = #($foo,$bar)
Start-Job -FilePath .\Prog\august\jobScript.ps1 -Name 'Test' -ArgumentList $myArray
}
#\Prog\august\jobScript.ps1 :
Param(
[array]$foo
)
#use $foo[0] and $foo[1] here
Still not working. I tried putting the info into an array and then passing only one parameter but still to know avail.
When I say no avail, I am getting the data that I need however it all seems to be compressed into the first element.
For example say I passed in the name of a file as $foo and it's path as $bar, for each method I tried, I would get args[0] as "filename path" and args[1] would be empty.
ie:
function Job-Test([string]$foo, [string]$bar){
$myArray = #($foo,$bar)
Start-Job -FilePath .\Prog\august\jobScript.ps1 -Name 'Test' -ArgumentList $myArray
}
Then I called:
$foo = "hello.txt"
$bar = "c:\users\world"
Job-Test($foo,$bar)
I had jobScript.ps1 simply Out-File the two variables to a log on separate lines and it looked like this:
log.txt:
hello.txt c:\users\world
#(empty line)
where it should have been:
hello.txt
c:\users\world
you don't need to call the function like you would in java. just append the two variables to the end of the function call Job-Test $foo $bar
I'm looking at writing some PowerShell code that can either execute immediately, or produce the commands it would execute as generated scripts.
I'd like to avoid this scenario:
if($Generating){
write-Output "somecommand.exe"
}
else{
somecommand.exe
}
I got looking at ScriptBlocks, which at first looked promising because I can write the contents of the ScriptBlock to the console without executing it. Such as:
$sc = { somecommand.exe }
$sc
somecommand.exe
My specific question is, if my scriptblock contains parameters, can I get them to resolve when I'm writing the scriptblock contents to the console, but WITHOUT invoking the scriptblock?
For example given the following scriptblock:
$b2 = { Param([string]$P) Write-Host "$P" }
When I just type "$b2" at the console and hit enter I see this:
Param([string]$P) Write-Host "$P"
What I'd like to see is this (if the parameter value is "Foo"):
Param([string]$P) Write-Host "Foo"
I realize this can be done when it's invoked, either via "&" or using Invoke(), but would there be any way to get the parameters to resolve without invoking to make my script generation a little more elegant without needing a bunch of conditional statements throughout the code?
In PowerShell v3, you can get the param info via the AST property e.g.:
PS> $sb = {param($a,$b) "a is $a b is $b"}
PS> $sb.Ast.ParamBlock
Attributes Parameters Extent Parent
---------- ---------- ------ ------
{} {$a, $b} param($a,$b) {param($a,$b) "a...
Solution suitable for PowerShell v2:
# given the script block
$b2 = { Param([string]$P) Write-Host "$P" }
# make a function of it and "install" in the current scope
Invoke-Expression "function tmp {$b2}"
# get the function and its parameters
(Get-Command tmp).Parameters
When displaying a here-string with double quotes #" , it expands the variables. For the variables that should'nt expand, escape the variable with a backtick ( ` ).
So try this:
$P = "Foo"
$b2 = #"
{ Param([string]`$P) Write-Host "$P" }
"#
Test:
PS-ADMIN > $b2
{ Param([string]$P) Write-Host "Foo" }
If you want to convert it to scriptblock-type again:
#Convert it into scriptblock
$b3 = [Scriptblock]::Create($b2)
PS-ADMIN > $b3
{ Param([string]$P) Write-Host "Foo" }
PS-ADMIN > $b3.GetType().name
ScriptBlock
Using some of the suggestions I think I've found the best solution for my needs. Consider the following code
function TestFunc
{
Param(
[Parameter(Mandatory=$true)]
[string]$Folder,
[Parameter(Mandatory=$true)]
[string]$Foo
)
$code = #"
Write-Host "This is a folder $Folder"
Write-Host "This is the value of Foo $Foo"
"#
$block = [Scriptblock]::Create($code)
Write-Host "Running the block" -BackgroundColor Green -ForegroundColor Black
&$block
Write-Host "Displaying block code" -BackgroundColor Green -ForegroundColor Black
$block
}
And it's output:
Running the block
This is a folder c:\some\folder
This is the value of Foo FOOFOO
Displaying block code
Write-Host "This is a folder c:\some\folder"
Write-Host "This is the value of Foo FOOFOO"
By doing it this way, I still get all the benefit of keeping my existing functions and their parameters, parameter validation, CBH etc. I can also easily generate the code that the function would execute or just let it execute. Thanks for all the input, it's definitely been a good learning experience.
If you want to express your block as a block, not a string, the following works:
$printable = invoke-expression ('"' + ($block -replace '"', '`"') + '"')
Essentially, you're wrapping everything in quotes and then invoking it as an expression. The -replace call ensures any quotes in the block itself are escaped.
I'm using this in this handy function, which also halts execution if the invoked command failed.
# usage: exec { dir $myDir }
function exec($block)
{
# expand variables in block so it's easier to see what we're doing
$printable = invoke-expression ('"' + ($block -replace '"', '`"').Trim() + '"')
write-host "# $printable" -foregroundcolor gray
& $block
if ($lastExitCode -ne 0)
{
throw "Command failed: $printable in $(pwd) returned $lastExitCode"
}
}