Powershell starting a process within a loop - powershell

I am trying to write a load balanced powershell publishing script and have seem to hit a roadblock. The foreach loop below will spin up a process to deploy using MSDeploy given the arguments.
foreach ($server in $ServersToDeploy) {
# Spin up a new process
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = $MSDeploy
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = $arguments
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$p.WaitForExit()
$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()
# Output
if ($stderr) {
throw $stderr + ("Exit Code: " + $p.ExitCode)
}
Write-Host $stdout
}
On the first run, it will run the script and execute MSDeploy with the proper arguments, but powershell would indefinitely wait for the first process to exit, but the publish seems to have executed successfully for both servers because when I re-run the command, the process executes quickly and properly for both servers with no changes.
This makes me think that this might be a timing issue, because when the publish goes through fast, it seems to work but when it's slow, it hangs on the first iteration of the publish.

Move the ReadToEnd calls above the WaitForExit
...
$p.Start() | Out-Null
$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()
$p.WaitForExit()
...

Related

WRSA.exe is throwing exitcode 2 while running through powershell

I have Webroot installed in my machine and I wrote a powershell script to automate the silentscan of the specific location.
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = "C:\Program Files (x86)\Webroot\WRSA.exe"
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = "-silentscan=C:\Program files"
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start()
$p.WaitForExit()
$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()
$exitcode = $p.ExitCode
Write-Output $Exitcode
WRSA.exe file was executed properly, but as a result it is showing 2 as an Exit code. is it correct exit code or is there any issue in the script?
Arguments that you pass are not escaped, try:
$pinfo.Arguments = ' -silentscan="C:\Program files" '

How to get output from Start-Process [duplicate]

Is there a bug in PowerShell's Start-Process command when accessing the StandardError and StandardOutput properties?
If I run the following I get no output:
$process = Start-Process -FilePath ping -ArgumentList localhost -NoNewWindow -PassThru -Wait
$process.StandardOutput
$process.StandardError
But if I redirect the output to a file I get the expected result:
$process = Start-Process -FilePath ping -ArgumentList localhost -NoNewWindow -PassThru -Wait -RedirectStandardOutput stdout.txt -RedirectStandardError stderr.txt
That's how Start-Process was designed for some reason. Here's a way to get it without sending to file:
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = "ping.exe"
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = "localhost"
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$p.WaitForExit()
$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()
Write-Host "stdout: $stdout"
Write-Host "stderr: $stderr"
Write-Host "exit code: " + $p.ExitCode
In the code given in the question, I think that reading the ExitCode property of the initiation variable should work.
$process = Start-Process -FilePath ping -ArgumentList localhost -NoNewWindow -PassThru -Wait
$process.ExitCode
Note that (as in your example) you need to add the -PassThru and -Wait parameters (this caught me out for a while).
IMPORTANT:
We have been using the function as provided above by LPG.
However, this contains a bug you might encounter when you start a process that generates a lot of output. Due to this you might end up with a deadlock when using this function. Instead use the adapted version below:
Function Execute-Command ($commandTitle, $commandPath, $commandArguments)
{
Try {
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = $commandPath
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = $commandArguments
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
[pscustomobject]#{
commandTitle = $commandTitle
stdout = $p.StandardOutput.ReadToEnd()
stderr = $p.StandardError.ReadToEnd()
ExitCode = $p.ExitCode
}
$p.WaitForExit()
}
Catch {
exit
}
}
Further information on this issue can be found at MSDN:
A deadlock condition can result if the parent process calls p.WaitForExit before p.StandardError.ReadToEnd and the child process writes enough text to fill the redirected stream. The parent process would wait indefinitely for the child process to exit. The child process would wait indefinitely for the parent to read from the full StandardError stream.
I also had this issue and ended up using Andy's code to create a function to clean things up when multiple commands need to be run.
It'll return stderr, stdout, and exit codes as objects. One thing to note: the function won't accept .\ in the path; full paths must be used.
Function Execute-Command ($commandTitle, $commandPath, $commandArguments)
{
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = $commandPath
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = $commandArguments
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$p.WaitForExit()
[pscustomobject]#{
commandTitle = $commandTitle
stdout = $p.StandardOutput.ReadToEnd()
stderr = $p.StandardError.ReadToEnd()
ExitCode = $p.ExitCode
}
}
Here's how to use it:
$DisableACMonitorTimeOut = Execute-Command -commandTitle "Disable Monitor Timeout" -commandPath "C:\Windows\System32\powercfg.exe" -commandArguments " -x monitor-timeout-ac 0"
I really had troubles with those examples from Andy Arismendi and from LPG. You should always use:
$stdout = $p.StandardOutput.ReadToEnd()
before calling
$p.WaitForExit()
A full example is:
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = "ping.exe"
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = "localhost"
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()
$p.WaitForExit()
Write-Host "stdout: $stdout"
Write-Host "stderr: $stderr"
Write-Host "exit code: " + $p.ExitCode
Here's a kludgy way to get the output from another powershell process (serialized):
start-process -wait -nonewwindow powershell 'ps | Export-Clixml out.xml'
import-clixml out.xml
Let me emphasize -nonewwindow to get the standardoutput and standarderror, at least on the local screen:
start-process -wait cmd '/c dir' -nonewwindow
Volume in drive C is Windows
Volume Serial Number is 2AC6-626F
Directory of C:\users\me\foo
11/24/2022 11:40 AM <DIR> .
11/24/2022 11:40 AM <DIR> ..
11/24/2022 11:40 AM 330 file.json
1 File(s) 330 bytes
2 Dir(s) 25,042,915,328 bytes free
start-process -wait cmd '/c dir foo' -nonewwindow
Volume in drive C is Windows
Volume Serial Number is 2AC6-626F
Directory of C:\users\me\foo
File Not Found
Here's what I cooked up based on the examples posted by others on this thread. This version will hide the console window and provided options for output display.
function Invoke-Process {
[CmdletBinding(SupportsShouldProcess)]
param
(
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]$FilePath,
[Parameter()]
[ValidateNotNullOrEmpty()]
[string]$ArgumentList,
[ValidateSet("Full","StdOut","StdErr","ExitCode","None")]
[string]$DisplayLevel
)
$ErrorActionPreference = 'Stop'
try {
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = $FilePath
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.WindowStyle = 'Hidden'
$pinfo.CreateNoWindow = $true
$pinfo.Arguments = $ArgumentList
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$result = [pscustomobject]#{
Title = ($MyInvocation.MyCommand).Name
Command = $FilePath
Arguments = $ArgumentList
StdOut = $p.StandardOutput.ReadToEnd()
StdErr = $p.StandardError.ReadToEnd()
ExitCode = $p.ExitCode
}
$p.WaitForExit()
if (-not([string]::IsNullOrEmpty($DisplayLevel))) {
switch($DisplayLevel) {
"Full" { return $result; break }
"StdOut" { return $result.StdOut; break }
"StdErr" { return $result.StdErr; break }
"ExitCode" { return $result.ExitCode; break }
}
}
}
catch {
exit
}
}
Example: Invoke-Process -FilePath "FQPN" -ArgumentList "ARGS" -DisplayLevel Full
To get both stdout and stderr, I use:
Function GetProgramOutput([string]$exe, [string]$arguments)
{
$process = New-Object -TypeName System.Diagnostics.Process
$process.StartInfo.FileName = $exe
$process.StartInfo.Arguments = $arguments
$process.StartInfo.UseShellExecute = $false
$process.StartInfo.RedirectStandardOutput = $true
$process.StartInfo.RedirectStandardError = $true
$process.Start()
$output = $process.StandardOutput.ReadToEnd()
$err = $process.StandardError.ReadToEnd()
$process.WaitForExit()
$output
$err
}
$exe = "cmd"
$arguments = '/c echo hello 1>&2' #this writes 'hello' to stderr
$runResult = (GetProgramOutput $exe $arguments)
$stdout = $runResult[-2]
$stderr = $runResult[-1]
[System.Console]::WriteLine("Standard out: " + $stdout)
[System.Console]::WriteLine("Standard error: " + $stderr)
Improved Answer - as long as you're OK with Start-Job instead of Start-Process
It turns out that the STDOUT and STDERR are accumulated in string arrays $job.ChildJobs[0].Output and $job.ChildJobs[0].Erroras the script runs. So you can poll these values and write them out periodically. Somewhat of a hack maybe, but it works.
It's not a stream though, so you have to manually keep track of the starting index into the array.
This code is simpler than my original answer, and at the end you have the entire STDOUT in $job.ChildJobs[0].Output. And as a little bonus for this demo, the calling script is PS7 and the background job is PS5.
$scriptBlock = {
Param ([int]$param1, [int]$param2)
$PSVersionTable
Start-Sleep -Seconds 1
$param1 + $param2
}
$parameters = #{
ScriptBlock = $scriptBlock
ArgumentList = 1, 2
PSVersion = 5.1 # <-- remove this line for PS7
}
$timeoutSec = 5
$job = Start-Job #parameters
$job.ChildJobs[0].Output
$index = $job.ChildJobs[0].Output.Count
while ($job.JobStateInfo.State -eq [System.Management.Automation.JobState]::Running) {
Start-Sleep -Milliseconds 200
$job.ChildJobs[0].Output[$index]
$index = $job.ChildJobs[0].Output.Count
if (([DateTime]::Now - $job.PSBeginTime).TotalSeconds -gt $timeoutSec) {
throw "Job timed out."
}
}
As pointed out, my original answer can interleave the output. This is a limitation of event handling in PowerShell. It's not a fixable problem.
Original Answer, don't use - just leaving it here for interest
If there's a timeout, ReadToEnd() is not an option. You could do some fancy looping, but IMO the 'cleanest' way to do this is to ignore the streams. Hook the OutputDataReceived/ErrorDataReceived events instead, collecting the output. This approach also avoids the threading issues mentioned by others.
This is straightforward in C#, but it's tricky and verbose in Powershell. In particular, add_OutputDataReceived is not available for some reason. (Not sure if this is a bug or a feature, at least this seems to be the case in PowerShell 5.1.) To work around it you can use Register-ObjectEvent.
$stdout = New-Object System.Text.StringBuilder
$stderr = New-Object System.Text.StringBuilder
$proc = [System.Diagnostics.Process]#{
StartInfo = #{
FileName = 'ping.exe'
Arguments = 'google.com'
RedirectStandardOutput = $true
RedirectStandardError = $true
UseShellExecute = $false
WorkingDirectory = $PSScriptRoot
}
}
$stdoutEvent = Register-ObjectEvent $proc -EventName OutputDataReceived -MessageData $stdout -Action {
$Event.MessageData.AppendLine($Event.SourceEventArgs.Data)
}
$stderrEvent = Register-ObjectEvent $proc -EventName ErrorDataReceived -MessageData $stderr -Action {
$Event.MessageData.AppendLine($Event.SourceEventArgs.Data)
}
$proc.Start() | Out-Null
$proc.BeginOutputReadLine()
$proc.BeginErrorReadLine()
Wait-Process -Id $proc.Id -TimeoutSec 5
if ($proc.HasExited) {
$exitCode = $proc.ExitCode
}
else {
Stop-Process -Force -Id $proc.Id
$exitCode = -1
}
# Be sure to unregister. You have been warned.
Unregister-Event $stdoutEvent.Id
Unregister-Event $stderrEvent.Id
Write-Output $stdout.ToString()
Write-Output $stderr.ToString()
Write-Output "Exit code: $exitCode"
The code shown is the happy path (stderr is empty)
To test the timeout path, set -TimeoutSec to .5
To test the sad path (stderr has content), set FileName to 'cmd' and Arguments to /C asdf
Here is my version of function that is returning standard System.Diagnostics.Process with 3 new properties
Function Execute-Command ($commandTitle, $commandPath, $commandArguments)
{
Try {
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = $commandPath
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.WindowStyle = 'Hidden'
$pinfo.CreateNoWindow = $True
$pinfo.Arguments = $commandArguments
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()
$p.WaitForExit()
$p | Add-Member "commandTitle" $commandTitle
$p | Add-Member "stdout" $stdout
$p | Add-Member "stderr" $stderr
}
Catch {
}
$p
}
You may want to also consider using the & operator combined with --% instead of start-process - that lets you easily pipe and process the command and/or error output.
put the escape parameter into a variable
put the arguments into a variable
$deploy= "C:\Program Files\IIS\Microsoft Web Deploy V3\msdeploy.exe"
$esc = '--%'
$arguments ="-source:package='c:\temp\pkg.zip' -verb:sync"
$output = & $deploy $esc $arguments
That passes the parameters to the executable without interference and let me get around the issues with start-process.
Combine Stderr and Stdout into one variable:
$output = & $deploy $esc $arguments 2>&1
Get separate variables for Stderr and Stdout
$err = $( $output = & $deploy $esc $arguments) 2>&1

Explicitly calling program create new window and doesn't work

I need to obtain the version of Maven's binary but using an explicit call to the program bring up a secondary windows and doesn't work.
In this case, it spawns a new window and returns nothing:
# spawns a new window with an error
# wanted to be more explicit in my call to the program
Write-Host "Maven..."
$x = & 'C:\path\to\maven\bin\mvn' '-version' 2>&1
Write-Host "out: "$x
In this case, it works as intended, but I have to assume the environment variable is configured:
# works as intended
# implies path is set
Write-Host "Maven..."
$x = & 'mvn' '-version' 2>&1
Write-Host "out: "$x
Any reasons why this is happening? Ideally, I'd like the first method to work.
Edit #1
Been trying the following, using Start-Process (from Capturing standard out and error with Start-Process)
Try {
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = "C:\path\to\maven\bin\mvn"
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = "-version"
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$stdout = $p.StandardOutput.ReadToEnd()
#$stderr = $p.StandardError.ReadToEnd()
#$exitCode = $p.ExitCode
$p.WaitForExit()
Write-host "out: "$stdout
}
Catch {
Write-Host $_.Exception.Message
}
I get this error:
Exception calling "Start" with "0" argument(s): "The specified
executable is not a valid application for this OS platfor m."

Redirect stderr only, keep stdout directed to console using System.Diagnostics.Process

I am using System.Diagnostics.Process as it allows me to get the error code and associated error.
However, when I set StartInfo.RedirectStandardOutput = $false output is not echoed to my console window, so currently I am forced to add an extra by-ref argument $stdout and echo it from the calling function.
This is not ideal as some commands may generate a huge amount of text, and I am worried about buffer overflows.
Any way that I can still use similar System.Diagnostics.Process code below, still capture errors to string, but let output flow to console normally without redirection to stdout?
function Run([string] $runCommand,[string] $runArguments,[ref] [string] $stderr)
{
$p = New-Object System.Diagnostics.Process
$p.StartInfo = New-Object System.Diagnostics.ProcessStartInfo;
$p.StartInfo.FileName = $runCommand
$p.StartInfo.Arguments = $runArguments
$p.StartInfo.CreateNoWindow = $true
$p.StartInfo.RedirectStandardError = $true
$p.StartInfo.RedirectStandardOutput = $false
$p.StartInfo.UseShellExecute = $false
$p.Start() | Out-Null
$p.WaitForExit()
$code = $p.ExitCode
$stderr.value = $p.StandardError.ReadToEnd()
# what I have been doing is using a stdout by-ref variable and echoing out contents
# $stdout.value = $p.StandardOutput.ReadToEnd()
return $code
}
You may not need to use the System.Diagnostics.Process object. Just execute the EXE and scoop up the info like this:
$stdout = .\foo.exe 2> fooerr.txt
Get-Content fooerr.txt
return $LastExitCode

Running a process using New-Object hides it

I have a need to grab the stdout from an external program and bring it back into Powershell. I found and am using the answer provided by #Andy Arismendi from this question ( Redirection of standard and error output appending to the same log-file).
The snippet below works great for me, however the external executable runs silently in the background. Is there a way to prevent it from hiding?
$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = "myjob.bat"
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = ""
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo
$p.Start() | Out-Null
$p.WaitForExit()
$output = $p.StandardOutput.ReadToEnd()
$output += $p.StandardError.ReadToEnd()
$output | Out-File $myLog -Append
Yes, you can set UseShellExecute to true, but you cannot redirect the input and output streams, then.