I'm trying to set up a Windows PowerShell alias to run MinGW's g++ executable with certain parameters. However, these parameters need to come after the file name and other arguments. I don't want to go through the hassle of trying to set up a function and all of that. Is there a way to simply say something like:
alias mybuild="g++ {args} -lib1 -lib2 ..."
or something along those lines? I am not all that familiar with PowerShell, and I'm having a difficult time finding a solution. Anyone?
You want to use a function, not an alias, as Roman mentioned. Something like this:
function mybuild { g++ $args -lib1 -lib2 ... }
To try this out, here's a simple example:
PS> function docmd { cmd /c $args there }
PS> docmd echo hello
hello there
PS>
You might also want to put this in your profile in order to have it available whenever you run PowerShell. The name of your profile file is contained in $profile.
There is not such a way built-in. IMHO, a wrapper function is the best way to go so far. But I know that some workarounds were invented, for example:
https://web.archive.org/web/20120213013609/http://huddledmasses.org/powershell-power-user-tips-bash-style-alias-command
To build an function, store it as an alias, and persist the whole thing in your profile for later, use:
$g=[guid]::NewGuid();
echo "function G$g { COMMANDS }; New-Alias -Force ALIAS G$g">>$profile
where you have replaced ALIAS with the alias you want and COMMANDS with the command or string of commands to execute.
Of course, instead of doing that you can (and should!) make an alias for the above by:
echo 'function myAlias {
$g=[guid]::NewGuid();
$alias = $args[0]; $commands = $args[1]
echo "function G$g { $commands }; New-Alias -Force $alias G$g">>$profile
}; New-Alias alias myAlias'>>$profile
Just in case your brain got turned inside out from all the recursion (aliasing of aliases, etc.), after pasting the second code block to your PowerShell (and restarting PowerShell), a simple example of using it is:
alias myEcho 'echo $args[0]'
or without args:
alias myLs 'ls D:\MyFolder'
Iff you don't have a profile yet
The above method will fail if you don't have a profile yet!
In that case, use New-Item -type file -path $profile -force from this answer.
This is a sample function that will do different things based on how it was called:
Function Do-Something {
[CmdletBinding()]
[Alias('DOIT')]
Param(
[string] $option1,
[string] $option2,
[int] $option3)
#$MyInvocation|select *|FL
If ($MyInvocation.InvocationName -eq 'DOIT'){write-host "You told me to do it...so i did!" -ForegroundColor Yellow}
Else {Write-Host "you were boring and said do something..." -ForegroundColor Green}
}
Creating a 'filter' is also an option, a lighter alternative to functions. It processes each element in the pipeline, assigning it the $_ automatic variable. So, for instance:
filter test { Write-Warning "$args $_" }
'foo','bar' | test 'This is'
returns:
WARNING: This is foo
WARNING: This is bar
Related
Forgive me, I am new to PowerShell in general. I'm updating a build process that works on Linux (in bash) to one that will work on Windows in PowerShell.
My goal is to get the version of the game engine currently present on the build system. The default build location is well-known, so we try to execute it and get the version, like so:
$Version = & 'C:\Program Files\LOVE\love.exe' --version
When this executes, the $Version value is empty:
Write-Output $Version
[no output]
$Version -Eq $True
False
If I run my executable directly from the shell, I notice the line is not presented on a newline:
PS C:\Users\robbm\Myproject\Mygame> $Version = & 'C:\Program Files\LOVE\love.exe' --version
PS C:\Users\robbm\Myproject\Mygame> LOVE 11.3 (Mysterious Mysteries)
This makes me suspect there is some strange output behavior with the executable in the first place.
Is this a problem with LÖVE's --version output, or am I misunderstanding something about redirecting outputs in PowerShell? I've tried a few things to capture output, and $Version always seems to end up a nil value, such as:
$Version = & '\\build\love\love.exe' '--version' | Out-String
Write-Output $Version
$Version = (& '\\build\love\love.exe' '--version' | Out-String)
Write-Output $Version
Help is appreciated. As this works for other cmdlets, I'm inclined to believe it might be a function of LÖVE, but I'd appreciate thoughts as to how I could work with this anyway, or any method in which to capture the version it's clearly outputting to the screen when I execute it directly regardless.
EDIT:
LÖVE definitely does something different in regards to running on Windows. Looking at the version printing source, we are working with the aptly-named LOVE_LEGENDARY_CONSOLE_IO_HACK enabled on Windows, which appears to open a new console entirely, perhaps in cmd and write out there.
Doing the suggestions of commenters, I tried doing the .Exception.Message method, but there is none when called like so:
$Version = &('C:\Program Files\LOVE\love.exe' '--version').Exception.Message
So I'm still looking for ways to make this work within the confines of LÖVE hacking together some strange I/O stream.
EDIT2:
Another fun fact, redirection to a file similarly fails:
PS> (&'C:\Program Files\LOVE\love.exe' '--version') 2>&1 > .\love.txt
PS> LOVE 11.3 (Mysterious Mysteries)
PS> cat .\love.txt
[empty]
So this looks to be overly hacky on behalf of LÖVE, not an issue with PowerShell.
After reading your last edit, this probably won't help you, but may help others.
You could try to capture the output like this:
function runCmdAndCaptureOutput(
[Parameter(Mandatory=$true)]
[string] $cmd
) {
[string] $errOut
[string] $stdOut
# Deliberately dropped '$' from vars below.
Invoke-Expression $cmd -ErrorVariable errOut -OutVariable stdOut
if($LASTEXITCODE -ne 0) {
Write-Host -ForegroundColor Red "LASTEXITCODE: $LASTEXITCODE"
throw $LASTEXITCODE
}
return $stdOut
}
$exeCmd = "'C:\Program Files\LOVE\love.exe' --version"
$output = runCmdAndCaptureOutput -cmd $exeCmd
Write-Host $output
Suppose I have the following code in a module (called MyModule.psm1, in the proper place for a module):
function new-function{
$greeting='hello world'
new-item -path function:\ -name write-greeting -value {write-output $greeting} -Options AllScope
write-greeting
}
After importing the module and running new-function I can successfully call the write-greeting function (created by new-function).
When I try to call the write-greeting function outside the scope of the new-function call, it fails because the function does not exist.
I've tried dot-sourcing new-function, but that doesn't help. I've supplied the -option Allscope, but apparently that only includes it in child scopes.
I've also tried explicitly following the new-item call with an export-modulemember write-greeting which doesn't give an error, but also doesn't create the function.
I want to be able to create a function dynamically (i.e. via new-item because the contents and name of the function will vary based on input) from a function inside a module and have the newly created function available to call outside of the module.
Specifically, I want to be able to do this:
Import-module MyModule
New-Function
write-greeting
and see "hello world" as output
Any ideas?
Making the function visible is pretty easy: just change the name of your function in New-Item to have the global: scope modifier:
new-item -path function:\ -name global:write-greeting -value {write-output $greeting} #-Options AllScope
You're going to have a new problem with your example, though, because $greeting will only exist in the new-function scope, which won't exist when you call write-greeting. You're defining the module with an unbound scriptblock, which means it will look for $greeting in its scope (it's not going to find it), then it will look in any parent scopes. It won't see the one from new-function, so the only way you'll get any output is if the module or global scope contain a $greeting variable.
I'm not exactly sure what your real dynamic functions will look like, but the easiest way to work around the new issue is to create a new closure around your scriptblock like this:
new-item -path function:\ -name global:write-greeting -value {write-output $greeting}.GetNewClosure()
That will create a new dynamic module with a copy of the state available at the time. Of course, that creates a new problem in that the function won't go away if you call Remove-Module MyModule. Without more information, I'm not sure if that's a problem for you or not...
You were close with needing to dot source, but you were missing Export-ModuleMember. Here is a complete example:
function new-function
{
$greeting='hello world'
Invoke-Expression "function write-greeting { write-output '$greeting' }"
write-greeting
}
. new-function
Export-ModuleMember -Function write-greeting
You also did not need or want -Scope AllScope.
Using the global: scope qualifier appears to work, but isn't the ideal solution. First, your function could stomp on another function in the global scope, which modules normally shouldn't do. Second, your global function would not be removed if you remove the module. Last - your global function won't be defined in the scope of the module, so if it needed access to non-exported functions or variables in your module, you can't (easily) get at them.
Thanks to the other solutions i was able to come up with a little helper that allows me to add plain script-files as functions and export them for the module in one step.
I have added the following function to my .psm1
function AddModuleFileAsFunction {
param (
[string] $Name,
[switch] $Export
)
$content = Get-Content (Join-Path $PSScriptRoot "$Name.ps1") -Raw
# Write-Host $content
$expression = #"
function $Name {
$content
}
"#
Invoke-Expression $expression
if ($Export) {
Export-ModuleMember -Function $Name
}
}
this allows me to load scripts as functions:
. AddModuleFileAsFunction "Get-WonderfulThings" -Export
( loads Get-WonderfulThings.ps1 body and exports it as function:Get-WonderfulThings )
I have a PowerShell script that I am debugging and would like to redirect all Write-Host statements to a file. Is there an easy way to do that?
Until PowerShell 4.0, Write-Host sends the objects to the host. It does not return any objects.
Beginning with PowerShell 5.0 and newer, Write-Host is a wrapper for Write-Information, which allows to output to the information stream and redirect it with 6>> file_name.
http://technet.microsoft.com/en-us/library/hh849877.aspx
However, if you have a lot of Write-Host statements, replace them all with Write-Log, which lets you decide whether output to console, file or event log, or all three.
Check also:
Add-Content
redirection operators like >, >>, 2>, 2>, 2>&1
Write-Log
Tee-Object
Start-Transcript.
You can create a proxy function for Write-Host which sends objects to the standard output stream instead of merely printing them. I wrote the below cmdlet for just this purpose. It will create a proxy on the fly which lasts only for the duration of the current pipeline.
A full writeup is on my blog here, but I've included the code below. Use the -Quiet switch to suppress the console write.
Usage:
PS> .\SomeScriptWithWriteHost.ps1 | Select-WriteHost | out-file .\data.log # Pipeline usage
PS> Select-WriteHost { .\SomeScriptWithWriteHost.ps1 } | out-file .\data.log # Scriptblock usage (safer)
function Select-WriteHost
{
[CmdletBinding(DefaultParameterSetName = 'FromPipeline')]
param(
[Parameter(ValueFromPipeline = $true, ParameterSetName = 'FromPipeline')]
[object] $InputObject,
[Parameter(Mandatory = $true, ParameterSetName = 'FromScriptblock', Position = 0)]
[ScriptBlock] $ScriptBlock,
[switch] $Quiet
)
begin
{
function Cleanup
{
# Clear out our proxy version of write-host
remove-item function:\write-host -ea 0
}
function ReplaceWriteHost([switch] $Quiet, [string] $Scope)
{
# Create a proxy for write-host
$metaData = New-Object System.Management.Automation.CommandMetaData (Get-Command 'Microsoft.PowerShell.Utility\Write-Host')
$proxy = [System.Management.Automation.ProxyCommand]::create($metaData)
# Change its behavior
$content = if($quiet)
{
# In quiet mode, whack the entire function body,
# simply pass input directly to the pipeline
$proxy -replace '(?s)\bbegin\b.+', '$Object'
}
else
{
# In noisy mode, pass input to the pipeline, but allow
# real Write-Host to process as well
$proxy -replace '(\$steppablePipeline\.Process)', '$Object; $1'
}
# Load our version into the specified scope
Invoke-Expression "function ${scope}:Write-Host { $content }"
}
Cleanup
# If we are running at the end of a pipeline, we need
# to immediately inject our version into global
# scope, so that everybody else in the pipeline
# uses it. This works great, but it is dangerous
# if we don't clean up properly.
if($pscmdlet.ParameterSetName -eq 'FromPipeline')
{
ReplaceWriteHost -Quiet:$quiet -Scope 'global'
}
}
process
{
# If a scriptblock was passed to us, then we can declare
# our version as local scope and let the runtime take
# it out of scope for us. It is much safer, but it
# won't work in the pipeline scenario.
#
# The scriptblock will inherit our version automatically
# as it's in a child scope.
if($pscmdlet.ParameterSetName -eq 'FromScriptBlock')
{
. ReplaceWriteHost -Quiet:$quiet -Scope 'local'
& $scriptblock
}
else
{
# In a pipeline scenario, just pass input along
$InputObject
}
}
end
{
Cleanup
}
}
You can run your script in a secondary PowerShell shell and capture the output like this:
powershell -File 'Your-Script.ps1' > output.log
That worked for me.
Using redirection will cause Write-Host to hang. This is because Write-Host deals with various formatting issues that are specific to the current terminal being used. If you just want your script to have flexibility to output as normal (default to shell, with capability for >, 2>, etc.), use Write-Output.
Otherwise, if you really want to capture the peculiarities of the current terminal, Start-Transcript is a good place to start. Otherwise you'll have to hand-test or write some complicated test suites.
Try adding a asterisk * before the angle bracket > to redirect all streams:
powershell -File Your-Script.ps1 *> output.log
When stream redirection is requested, if no specific stream is indicated then by default only the Success Stream(1>) is redirected. Write-Host is an alias for Write-Information which writes to the Information Stream (6>). To redirect all streams use *>.
Powershell-7.1 supports redirection of multiple output streams:
Success Stream (#1): PowerShell 2.0 Write-Output
Error Stream (#2): PowerShell 2.0 Write-Error
Warning Stream (#3): PowerShell 3.0 Write-Warning
Verbose Stream (#4): PowerShell 3.0 Write-Verbose
Debug Stream (#5): PowerShell 3.0 Write-Debug
Information Stream (#6): PowerShell 5.0 Write-Information
All Streams (*): PowerShell 3.0
This worked for me in my first PowerShell script that I wrote few days back:
function logMsg($msg)
{
Write-Output $msg
Write-Host $msg
}
Usage in a script:
logMsg("My error message")
logMsg("My info message")
PowerShell script execution call:
ps> .\myFirstScript.ps1 >> testOutputFile.txt
It's not exactly answer to this question, but it might help someone trying to achieve both logging to the console and output to some log file, doing what I reached here :)
Define a function called Write-Host. Have it write to a file. You may have some trouble if some invocations use a weird set of arguments. Also, this will only work for invocations that are not Snapin qualified.
If you have just a few Write-Host statements, you can use the "6>>" redirector operator to a file:
Write-Host "Your message." 6>> file_path_or_file_name
This is the "Example 5: Suppress output from Write-Host" provided by Microsoft, modified accordingly to about_Operators.
I just added Start-Transcript at the top of the script and Stop-Transcript at the bottom.
The output file was intended to be named <folder where script resides>-<datestamp>.rtf, but for some reason the trace file was being put where I did not expect it — the desktop!
You should not use Write-Host if you wish to have the messages in a file. It is for writing to the host only.
Instead you should use a logging module, or Set/Add-Content.
I have found the best way to handle this is to have a logging function that will detect if there is a host UI and act accordingly. When the script is executed in interactive mode it will show the details in the host UI, but when it is run via WinRM or in a non-interactive mode it will fall back on the Write-Output so that you can capture it using the > or *> redirection operators
function Log-Info ($msg, $color = "Blue") {
if($host.UI.RawUI.ForegroundColor -ne $null) {
Write-Host "`n[$([datetime]::Now.ToLongTimeString())] $msg" -ForegroundColor $color -BackgroundColor "Gray"
} else {
Write-Output "`r`n[$([datetime]::Now.ToLongTimeString())] $msg"
}
}
In cases where you want to capture the full output with the Write-Host coloring, you can use the Get-ConsoleAsHtml.ps1 script to export the host's scrolling buffer to an HTML or RTF file.
Use Write-Output instead of Write-Host, and redirect it to a file like this:
Deploy.ps1 > mylog.log or Write-Output "Hello World!" > mylog.log
Try using Write-Output instead of Write-Host.
The output goes down the pipeline, but if this is the end of the pipe, it goes to the console.
> Write-Output "test"
test
> Write-Output "test" > foo.txt
> Get-Content foo.txt
test
I'm trying to set up a Windows PowerShell alias to run MinGW's g++ executable with certain parameters. However, these parameters need to come after the file name and other arguments. I don't want to go through the hassle of trying to set up a function and all of that. Is there a way to simply say something like:
alias mybuild="g++ {args} -lib1 -lib2 ..."
or something along those lines? I am not all that familiar with PowerShell, and I'm having a difficult time finding a solution. Anyone?
You want to use a function, not an alias, as Roman mentioned. Something like this:
function mybuild { g++ $args -lib1 -lib2 ... }
To try this out, here's a simple example:
PS> function docmd { cmd /c $args there }
PS> docmd echo hello
hello there
PS>
You might also want to put this in your profile in order to have it available whenever you run PowerShell. The name of your profile file is contained in $profile.
There is not such a way built-in. IMHO, a wrapper function is the best way to go so far. But I know that some workarounds were invented, for example:
https://web.archive.org/web/20120213013609/http://huddledmasses.org/powershell-power-user-tips-bash-style-alias-command
To build an function, store it as an alias, and persist the whole thing in your profile for later, use:
$g=[guid]::NewGuid();
echo "function G$g { COMMANDS }; New-Alias -Force ALIAS G$g">>$profile
where you have replaced ALIAS with the alias you want and COMMANDS with the command or string of commands to execute.
Of course, instead of doing that you can (and should!) make an alias for the above by:
echo 'function myAlias {
$g=[guid]::NewGuid();
$alias = $args[0]; $commands = $args[1]
echo "function G$g { $commands }; New-Alias -Force $alias G$g">>$profile
}; New-Alias alias myAlias'>>$profile
Just in case your brain got turned inside out from all the recursion (aliasing of aliases, etc.), after pasting the second code block to your PowerShell (and restarting PowerShell), a simple example of using it is:
alias myEcho 'echo $args[0]'
or without args:
alias myLs 'ls D:\MyFolder'
Iff you don't have a profile yet
The above method will fail if you don't have a profile yet!
In that case, use New-Item -type file -path $profile -force from this answer.
This is a sample function that will do different things based on how it was called:
Function Do-Something {
[CmdletBinding()]
[Alias('DOIT')]
Param(
[string] $option1,
[string] $option2,
[int] $option3)
#$MyInvocation|select *|FL
If ($MyInvocation.InvocationName -eq 'DOIT'){write-host "You told me to do it...so i did!" -ForegroundColor Yellow}
Else {Write-Host "you were boring and said do something..." -ForegroundColor Green}
}
Creating a 'filter' is also an option, a lighter alternative to functions. It processes each element in the pipeline, assigning it the $_ automatic variable. So, for instance:
filter test { Write-Warning "$args $_" }
'foo','bar' | test 'This is'
returns:
WARNING: This is foo
WARNING: This is bar
Is it possible to test for the existence of a script-scoped variable in PowerShell?
I've been using the PowerShell Community Extensions (PSCX) but I've noticed that if you import the module while Set-PSDebug -Strict is set, an error is produced:
The variable '$SCRIPT:helpCache' cannot be retrieved because it has not been set.
At C:\Users\...\Modules\Pscx\Modules\GetHelp\Pscx.GetHelp.psm1:5 char:24
While investigating how I might fix this, I found this piece of code in Pscx.GetHelp.psm1:
#requires -version 2.0
param([string[]]$PreCacheList)
if ((!$SCRIPT:helpCache) -or $RefreshCache) {
$SCRIPT:helpCache = #{}
}
This is pretty straight forward code; if the cache doesn't exist or needs to be refreshed, create a new, empty cache. The problem is that calling $SCRIPT:helpCache while Set-PSDebug -Strict is in force casues the error because the variable hasn't been defined yet.
Ideally, we could use a Test-Variable cmdlet but such a thing doesn't exist! I thought about looking in the variable: provider but I don't know how to determine the scope of a variable.
So my question is: how can I test for the existence of a variable while Set-PSDebug -Strict is in force, without causing an error?
Use test-path variable:SCRIPT:helpCache
if (!(test-path variable:script:helpCache)) {
$script:helpCache = #{}
}
This works for me without problems.
Checked using this code:
#'
Set-PsDebug -strict
write-host (test-path variable:script:helpCache)
$script:helpCache = "this is test"
write-host (test-path variable:script:helpCache) and value is $script:helpCache
'# | set-content stricttest.ps1
.\stricttest.ps1
Try this trick:
Get-Variable [h]elpCache -Scope Script
It should not throw or emit any errors because we use a wildcard [h]elpCache. On the other hand this kind of a wildcard is a literal name de facto.
You can use Get-Variable with the -Scope parameter. This cmdlet will (by default at least) not return only the variable's value but a PSVariable object and will throw an exception if the variable isn't found:
Get-Variable foo -Scope script