This one is confusing me and wondered if anyone could shed some light on this, maybe also answer 2 parts with this one example?
I have a Powershell script I run like a batch file and I have it output values it has captured from a separate file out to a log. This particular part is not outputting in the transcript where I get the DB version of a database. I have tried different placements of the ", using $DBVersion on it's own and this is a simple way to show what I have trouble with. e.g.:
## Read the DBs Extended properties
Function Get-DB_Version {
Param (
$SQLInstance,
$DBName
)
Invoke-Sqlcmd -ServerInstance $SQLInstance -Database $DBName -Query "SELECT value FROM fn_listextendedproperty(default, default, default, default, default, default, default) WHERE name = 'version'"
}
**Other Variables used are also pre-set above here **
## Get DB version
$DBVersion = Get-DB_Version -SQLInstance $SQLInstance -DBName $DBName
Start-Transcript -Path "$LogOutput\$LogName" -IncludeInvocationHeader -Append
Write-Information "
**** DEBUG INFO ****
Write-Host "Debug:"$DBVersion.value
Write-Information "Debug:"$DBVersion.value
Read-Host -Prompt "PAUSE" # This is so I can visually see the console seeing only the write-host is there as expected.
Stop-Transcript
In my log file I get the output:
Debug: 2.16.51443.5147
INFO: Debug:
This shows me that the variable contains a value as the write-host outputs it, however when use Write-Information it does not show anything in the log, All other variables I use do show, why would $DBVersion.value or $DBVersion not show anything please?
Also the second part is, why do I have to use:
$DBVersion.value
Outside of the write-host "" quotes?
Many thank in Advance
As #abraham said in the comments. All I had to do, to have the variable inside of the quotes (my question 2) was use the sub-expression operator $() to expand the value inside the quotes: Write-Host "Debug: $($DBVersion.value)". The same goes for your Write-Information.
Doing this alone also resolved my original question of why Write-Information didn't output anything into the transaction logs and I did NOT need to change the $InformationPreference.
Related
We have a bunch of different powershell tools that we use for build/deploy and other development and admin activity in my team. Mostly these are calling other Powershell scripts and Cmdlets but there are some x86 command line apps also (e.g. msbuild)
They largely all are setup to output verbose output. I do that so that I can troubleshoot retrospectively when something goes wrong in the team
However the team have asked to have less noisy output to the console. I still want the verbose output to be available retrospectively
So it feels like I need something like a continuous loop of the last 100k rows of verbose activity. Including any console input and output written to a file - regardless of the -verbose setting that the developer applied
Is there anything like this available in Powershell?
I know about redirection but I'm not sure how it can solve this problem as it seems that you have to match the stdout with the redirect even if you use Tee-Object - also it wouldn't capture inputs.
Eager to learn some hidden secrets or elegant creative solutions! :)
UPDATE: as mentioned redirect is not a practical solution. I've created a request https://github.com/PowerShell/PowerShell/issues/17482
An article that addresses this topic is about_Redirection. Each output stream has a numeric identifier - the range is 1 to 6. The referenced article has a table showing the mapping between the ID's and streams.
Write-Host's ID is 6, so if you wanted everything to go to a log file except that, you can try redirecting all streams except 6:
PS:> Start-VeryNoiseyOperation -Debug 1>C:\mylogs\noisey.log 2>&1 3>&1 4>&1 5>&1
This example is redirecting all streams generated by the Write-____ cmdlets, except Write-Host and Write-Information. To send all streams to the log file, you can use *>C:\mylogs\noisey.log.
If you want to experiment, you can run this function with different combos of redirection to see the effect.
PS:> function Foo {
[CmdletBinding()]param()
Write-Output #{message = "my printed object"} # 1
Write-Error "This is an error message." # 2
Write-Warning "This is a warning message." # 3
Write-Verbose "This is a verbose message." # 4
Write-Debug "This is a debug message." # 5
Write-Host "This is a host message." # 6
}
PS:> $log = New-TemporaryFile
PS:> $logPath = $log.FullName
PS:>
PS:> Foo -Debug -Verbose # Print everything.
:
PS:> Foo -Debug -Verbose 1>$logPath # Send object stream to file.
:
PS:> Get-Content $logPath # Object should print to console.
:
PS:> Foo -Debug -Verbose 1>$logPath 2>&1 # Try different combos.
: # see effect on console output #
PS:> Get-Content $logPath
: # see log content #
i just started with Powershell and have already a problem.
I am using the API from OpenWeathermap (https://openweathermap.org/) to create something like a weather-bot.
I am using this function from the API:
Write-WeatherCurrent -City $place -ApiKey $ApiKey -Units metric
Where the Output something like this (if I fill the Variables):
10.2°C (☁️ few clouds) in london
So I want this Output to save in a File. I already tried with the Commands Out-File and >>. But it only outputs in the Terminal and the File is empty. I am not sure, but is it because of "Write"-WeatherCurrent?
I would be happy if anybody could help me :D
Thank you
Write-WeatherCurrent uses Write-Host to write the output directly to the host console buffer.
If you're using PowerShell 5.0 or newer, you can capture the Write-Host output to a variable with the InformationVariable common parameter:
Write-WeatherCurrent -City $place -ApiKey $ApiKey -Units metric -InformationVariable weatherInfo
$weatherInfo now contains the string output and you can write it to file:
$weatherInfo |Out-File path\to\file.txt
If the target command doesn't expose common parameters, another option is to merge the Information stream into the standard output stream:
$weatherInfo = Write-WeatherCurrent -City $place -ApiKey $ApiKey -Units metric 6>&1 # "stream 6" is the Information stream
What is the difference between Write-Host and Write-Output in PowerShell?
Like...
Write-Host "Hello World";
Write-Output "Hello World";
In a nutshell, Write-Host writes to the console itself. Think of it as a MsgBox in VBScript. Write-Output, on the other hand, writes to the pipeline, so the next command can accept it as its input. You are not required to use Write-Output in order to write objects, as Write-Output is implicitly called for you.
PS> Get-Service
would be the same as:
PS> Get-Service | Write-Output
Write-Output sends the output to the pipeline. From there it can be piped to another cmdlet or assigned to a variable.
Write-Host sends it directly to the console.
$a = 'Testing Write-OutPut' | Write-Output
$b = 'Testing Write-Host' | Write-Host
Get-Variable a,b
Outputs:
Testing Write-Host
Name Value
---- -----
a Testing Write-OutPut
b
If you don't tell Powershell what to do with the output to the pipeline by assigning it to a variable or piping it to anoher command, then it gets sent to out-default, which is normally the console so the end result appears the same.
Write-Output sends the data as an object through the pipeline. In the Questions example it will just pass a string.
Write-Host is host dependent. In the console Write-Host is essentially doing [console]::WriteLine.
See this for more info.
Another difference between Write-Host and Write-Output:
Write-Host displays the message on the screen, but it does not write it to the log
Write-Output writes a message to the log, but it does not display it on the screen.
And Write-Host is considered as harmful. You can see a detailed explanation in Write-Host Considered Harmful.
You can understand the difference between the two cmds with below example:
Write-host "msgtxt" | Get-Service
On running above, you will get output as "msgtxt"
Write-output "msgtxt" | Get-Service
On running above, you will receive an error since msgtxt is not the name of any service.( In ideal condition) (Since you are writing it to a pipeline and it is being passed as input to Get-Service)
One more thing about Write-Host vs Write-Output: inline String concatenation may not work as expected.
$sampleText = "World"
Write-Host "Hello" $sampleText
returns
Hello World
but
$sampleText = "World"
Write-Output "Hello" $sampleText
returns
Hello
World
This would encourage Write-Output with a variable (and use of concatenation) holding the entire string at once.
$hw = "Hello " + $sampleText
Write-Output $hw
Is there any sane, reliable contract that dictates whether Write-Host is supported in a given PowerShell host implementation, in a script that could be run against any reasonable host implementation?
(Assume that I understand the difference between Write-Host and Write-Output/Write-Verbose and that I definitely do want Write-Host semantics, if supported, for this specific human-readable text.)
I thought about trying to interrogate the $Host variable, or $Host.UI/$Host.UI.RawUI but the only pertinent differences I am spotting are:
in $Host.Name:
The Windows powershell.exe commandline has $Host.Name = 'ConsoleHost'
ISE has $Host.Name = 'Windows PowerShell ISE Host'
SQL Server Agent job steps have $Host.Name = 'Default Host'
I have none of the non-Windows versions installed, but I expect they are different
in $Host.UI.RawUI:
The Windows powershell.exe commandline returns values for all properties of $Host.UI.RawUI
ISE returns no value (or $null) for some properties of $Host.UI.RawUI, e.g. $Host.UI.RawUI.CursorSize
SQL Server Agent job steps return no values for all of $Host.UI.RawUI
Again, I can't check in any of the other platforms
Maintaining a list of $Host.Name values that support Write-Host seems like it would be bit of a burden, especially with PowerShell being cross-platform now. I would reasonably want the script to be able to be called from any host and just do the right thing.
Background
I have written a script that can be reasonably run from within the PowerShell command prompt, from within the ISE or from within a SQL Server Agent job. The output of this script is entirely textual, for human reading. When run from the command prompt or ISE, the output is colorized using Write-Host.
SQL Server jobs can be set up in two different ways, and both support capturing the output into the SQL Server Agent log viewer:
via a CmdExec step, which is simple command-line execution, where the Job Step command text is an executable and its arguments, so you invoke the powershell.exe executable. Captured output is the stdout/sterr of the process:
powershell.exe -Command x:\pathto\script.ps1 -Arg1 -Arg2 -Etc
via a PowerShell step, where the Job Step command text is raw PS script interpreted by its own embedded PowerShell host implementation. Captured output is whatever is written via Write-Output or Write-Error:
#whatever
Do-WhateverPowershellCommandYouWant
x:\pathto\script.ps1 -Arg1 -Arg2 -Etc
Due to some other foibles of the SQL Server host implementation, I find that you can emit output using either Write-Output or Write-Error, but not both. If the job step fails (i.e. if you throw or Write-Error 'foo' -EA 'Stop'), you only get the error stream in the log and, if it succeeds, you only get the output stream in the log.
Additionally, the embedded PS implementation does not support Write-Host. Up to at least SQL Server 2016, Write-Host throws a System.Management.Automation.Host.HostException with the message A command that prompts the user failed because the host program or the command type does not support user interaction.
To support all of my use-cases, so far, I took to using a custom function Write-Message which was essentially set up like (simplified):
$script:can_write_host = $true
$script:has_errors = $false
$script:message_stream = New-Object Text.StringBuilder
function Write-Message {
Param($message, [Switch]$iserror)
if ($script:can_write_host) {
$private:color = if ($iserror) { 'Red' } else { 'White' }
try { Write-Host $message -ForegroundColor $private:color }
catch [Management.Automation.Host.HostException] { $script:can_write_host = $false }
}
if (-not $script:can_write_host) {
$script:message_stream.AppendLine($message) | Out-Null
}
if ($iserror) { $script:has_errors = $true }
}
try {
<# MAIN SCRIPT BODY RUNS HERE #>
}
catch {
Write-Message -Message ("Unhandled error: " + ($_ | Format-List | Out-String)) -IsError
}
finally {
if (-not $script:can_write_host) {
if ($script:has_errors) { Write-Error ($script:message_stream.ToString()) -EA 'Stop' }
else { Write-Output ($script:message_stream.ToString()) }
}
}
As of SQL Server 2019 (perhaps earlier), it appears Write-Host no longer throws an exception in the embedded SQL Server Agent PS host, but is instead a no-op that emits nothing to either output or error streams. Since there is no exception, my script's Write-Message function can no longer reliably detect whether it should use Write-Host or StringBuilder.AppendLine.
The basic workaround for SQL Server Agent jobs is to use the more-mature CmdExec step type (where Write-Output and Write-Host both get captured as stdout), but I do prefer the PowerShell step type for (among other reasons) its ability to split the command reliably across multiple lines, so I am keen to see if there is a more-holistic, PowerShell-based approach to solve the problem of whether Write-Host does anything useful for the host I am in.
Just check if your host is UserInteractive or an service type environment.
$script:can_write_host = [Environment]::UserInteractive
Another way to track the output of a script in real time is to push that output to a log file and then monitor it in real time using trace32. This is just a workaround, but it might work out for you.
Add-Content -Path "C:\Users\username\Documents\PS_log.log" -Value $variablewithvalue
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