using powershell invoke-expression to run code output - powershell

I have been doing a lot of reading on invoke-expression (also known as iex) and I'm having trouble getting it to work for me.
My understanding is, it will run any powershell code you give to it. However, when I run my tests on it, it does not run the code.
Example:
## testcode.ps1
$myvar = "i am here"
if ($myvar -ne $null) {
"($myvar) variable is Full"
} else {
"($myvar) variable is Empty"
}
Now, if I cat(gc) this file and I pass it to iex, it outputs a bunch of errors. Same thing happens when I save the code into a variable and then feed the variable to iex. Neither works.
Despite the fact that I've tried numerous examples, I feel there's something minor I'm doing wrong that I'm hoping someone can point out for me.
I'm new to Windows scripting, so please bear with me. These are the results of the tests I performed:
First Test:
PS C:\Users\J> gc C:\Users\J\testcode.ps1 | iex
Invoke-Expression : Cannot bind argument to parameter 'Command' because it is an empty string.
At line:1 char:31
+ cat C:\Users\J\testcode.ps1 | iex
+ ~~~
+ CategoryInfo : InvalidData: (:PSObject) [Invoke-Expression], ParameterBindingValidationException
+ FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,Microsoft.PowerShell.Commands.InvokeExpressionCommand
iex : At line:1 char:23
+ if ($myvar -ne $null) {
+ ~
Missing closing '}' in statement block or type definition.
At line:1 char:31
+ cat C:\Users\J\testcode.ps1 | iex
+ ~~~
+ CategoryInfo : ParserError: (:) [Invoke-Expression], ParseException
+ FullyQualifiedErrorId : MissingEndCurlyBrace,Microsoft.PowerShell.Commands.InvokeExpressionCommand
Second Test:
PS C:\Users\J> $scriptBlock = gc C:\Users\J\testcode.ps1
PS C:\Users\J>
PS C:\Users\J> iex -Command "$scriptBlock"
iex : At line:1 char:23
+ $myvar = "i am here" if ($myvar -ne $null) { "($myvar) variable ...
+ ~~
Unexpected token 'if' in expression or statement.
At line:1 char:1
+ iex -Command "$scriptBlock"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : ParserError: (:) [Invoke-Expression], ParseException
+ FullyQualifiedErrorId : UnexpectedToken,Microsoft.PowerShell.Commands.InvokeExpressionCommand
PS C:\Users\J>
I'm aware that I can just run the file containing the code. However, I need help figuring out how iex works and what it is I'm doing wrong.
Please kindly advise.

First things first:
Invoke-Expression should generally be avoided and used only as a last resort, due to its security risks. In short: avoid it, if possible, given that superior alternatives are usually available. If there truly is no alternative, only ever use it on input you either provided yourself or fully trust - see this answer.
For the record: in the case at hand, the superior alternative is to directly invoke the script file:
# Prepend `& `, if the script file path is quoted or references a variable.
C:\Users\J\testcode.ps1
Invoke-Expression (iex) accepts multiple strings via the pipeline, and evaluates each individually, as a self-contained script.
Therefore, you must provide the contents of your script as a whole, as a single string, which is what Get-Content's (gc's) -Raw switch does[1]:
Get-Content -Raw C:\Users\J\testcode.ps1 | Invoke-Expression
Alternatively, pass the script-file contents as an argument:
Invoke-Expression (Get-Content -Raw C:\Users\J\testcode.ps1)
Note that passing the string to evaluate as an argument truly only accepts a single string, so the command would fail without -Raw.
[1] By default, the Get-Content cmdlet reads a file line by line, passing each line through the pipeline as it is being read.

$myvar = "I'm Here"
#Using Invoke-Expression - Accepts a STRING as Input
$SBCode = 'if ($Null -ne $myvar) {"($myvar) variable is Full"}' +
'else {"`$myvar variable is Empty"}'
Clear-Host
"Before Invoke-Expression `$myvar = $myvar"
$Result = Invoke-Expression $SBCode
"Invoke-Expression Returns: $Result"
#Using Invoke-Command - Accepts Script Block as Input
$SBCode = {
if ($myvar -ne $null) {
"($myvar) variable is Full"
}
else {
"`$myvar variable is Empty"
}
} #End $SBCode Script Block
"Before Invoke-Command `$myvar = $myvar"
$Result = Invoke-Command -ScriptBlock $SBCode
"Invoke-Command Returns: $Result"
Results:
Before Invoke-Expression $myvar = I'm Here
Invoke-Expression Returns: (I'm Here) variable is Full
Before Invoke-Command $myvar = I'm Here
Invoke-Command Returns: (I'm Here) variable is Full
# After changing $MyVar = $Null
Before Invoke-Expression $myvar =
Invoke-Expression Returns: $myvar variable is Empty
Before Invoke-Command $myvar =
Invoke-Command Returns: $myvar variable is Empty
HTH

You can use out-string to convert output into string.
cat C:\Users\J\testcode.ps1 | out-string | Invoke-Expression

Related

String comparison not working in powershell

I am trying an if else condition in powershell using string comparison. I tried as per documentation using -eq operator. But getting below error. Here "Build.Reason" is a predefined variable. Not sure why its looking for cmdlet name for variable.
Write-Host "$(Build.Reason)"
if ($(Build.Reason) -eq "Manual" ) {
$temp = "https://url/api/qualitygates/project_status?&pullRequest=$(Build.Reason)"
Write-Host "Manual"
} else {
Write-Host "CI"
}
Error
"C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -NoLogo -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command ". 'D:\a\_temp\d7af16d6-ce3e-4dec-a636-9447962fdac4.ps1'"
Manual
Manual : The term 'Manual' is not recognized as the name of a cmdlet, function, script file, or operable program.
Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At D:\a\_temp\d7af16d6-ce3e-4dec-a636-9447962fdac4.ps1:7 char:5
+ if (Manual -eq "Manual" ) {
+ ~~~~~~
+ CategoryInfo : ObjectNotFound: (Manual:String) [], ParentContainsErrorRecordException
+ FullyQualifiedErrorId : CommandNotFoundException
It looks like $(Build.Reason) is a macro-style value provide by a CI system (it is not a PowerShell construct), which is expanded to become a literal part of the code before PowerShell sees it.
Therefore, if this value is to be treated as a string in the resulting PowerShell code, you need to quote it; e.g.:
if ("$(Build.Reason)" -eq "Manual") { # ...
Note that if there's a chance that $(Build.Reason) expands to a value with embedded " characters, they would have to be escaped as `". Similarly, if the value contains embedded $ chars., single-quoting should be used, which may then require escaping embedded single quotes as ''.
If this escaping cannot be performed at the source, you can use a verbatim here-string:
if (#'
$(Build.Reason)
'# -eq 'Manual') { # ...
Important: The closing '# must always be at the very beginning of the line.

powershell : pipe get-content to ps1 file with parameters

I'm trying to write a script which uses the powershell cmdlet get-content tail and inserts the new lines into the sql server table. i can't get the syntax to pipe the tail to the sqlinsert.ps1 file that handles the table insert.
i'm looking for help on how to pipe "get-content tail" to a sqlinsert.ps1 file to do a sql database insert statement using the following :
$startTime = get-date
Write-Host "\\iisserver\logs\Logs-$("{0:yyyyMMdd}" -f (get-date)).txt"
get-content "\\iisserver\logs\Logs-$("{0:yyyyMMdd}" -f (get-date)).txt" -tail 1 -wait | & "sqlinsert.ps1" -stmp $("{0:yyyy-MM-dd hh:mm:ss.fff}" -f (get-date)) -method "Error" -msg $_
# % { "$_ read at $(Get-Date -Format "hh:mm:ss")" }
in the sqlinsert.ps1 :
param ([string]$stmp, [string]$method, [string]$msg )
$Connection = New-Object System.Data.SQLClient.SQLConnection
$Connection.ConnectionString = "server='$serverName';database='$databaseName';User ID = $uid; Password = $pwd;"
$Command = New-Object System.Data.SQLClient.SQLCommand
$Command.Connection = $Connection
$sql = "insert into [tbl_iiserrors] (errstamp, method, msg) values (#stmp , #method, #msg) "
.
.
.
error i get:
& : The term 'sqlinsert.ps1' is not recognized as the name of a
cmdlet, function, script file, or operable program. Check the spelling
of the name, or if a path was included, verify that the path is
correct and try again. At C:\Temp\ob\iislog\tst_tail.ps1:3 char:95
... Mdd}" -f (get-date)).txt" -tail 1 -wait | & "sqlinsert.ps1" -stmp $ ...
~~~~~~~~~~~~~~~
CategoryInfo : ObjectNotFound: (sqlinsert.ps1:String) [], CommandNotFoundException
FullyQualifiedErrorId : CommandNotFoundException
Suggestion [3,General]: The command sqlinsert.ps1 was not found, but
does exist in the current location. Windows PowerShell does not load
commands from the current location by default. If you trust this
command, instead type: ".\sqlinsert.ps1". See "get-help
about_Command_Precedence" for more details.
The sqlinsert.ps1 works when i run it from powershell command :
PS c:\temp> .\sqlinsert -stmp 2020-11-20 00:00:00 -method 'eek' -msg 'uh hello'
In order to bind pipeline input to a parameter, you need to decorate it with a [Parameter] attribute and specify that it accepts pipeline input, like this:
param (
[string]$stmp,
[string]$method,
[Parameter(ValueFromPipeline = $true)]
[string]$msg
)
See the about_Functions_Advanced_Parameters help file for more details about how to modify the behavior of parameters
By design, for security reasons, PowerShell requires you to signal the intent to execute a script located in the current directory explicitly, using a path - .\sqlinsert.ps1 - rather than a mere file name - sqlinsert.ps1; that is what the suggestion following the error message is trying to tell you.
Note that you only need &, the call operator, if the script path is quoted and/or contains variable references - and .\sqlinsert.ps1 doesn't require quoting.
You can only use the automatic $_ variable, which represents the current input object from the pipeline inside a script block ({ ... }), such as one passed to the ForEach-Object cmdlet, which invokes that block for each object received via the pipeline.
Re the content of your script: Inside expandable strings ("..."), you cannot use # to refer to variables to be expanded (interpolated); use regular, $-prefixed variable references or $(...), the subexpression operator to embed expressions; also, it looks like you're inserting string values into the SQL table, so you'll have to enclose the expanded variable values in embedded '...'
$startTime = get-date
Get-Content "\\iisserver\logs\Logs-$("{0:yyyyMMdd}" -f (get-date)).txt" -Tail 1 -Wait |
ForEach-Object {
.\sqlinsert.ps1 -stmp ("{0:yyyy-MM-dd hh:mm:ss.fff}" -f (get-date)) -method "Error" -msg $_
}
The alternative to using a ForEach-Object call is to modify your script to directly receive its -msg argument from the pipeline, as shown in Mathias' answer, in which case you must omit the -msg $_ argument from your script call:
Get-Content ... |
.\sqlinsert.ps1 -stmp ("{0:yyyy-MM-dd hh:mm:ss.fff}" -f (get-date)) -method "Error"

PowerShell Split-Job empty pipe element not allowed

I would really like to use the function Split-Job to throttle or run the same script block in parallel, so it goes quicker. This is especially useful when I need to launch multiple times the same copy command on different input.
The code can be found here and always spits out the following error:
An empty pipe element is not allowed.
+ CategoryInfo : ParserError: (:) [], ParentContainsErrorRecordException
+ FullyQualifiedErrorId : EmptyPipeElement
I know the problem is within this function, but I can't seem to solve it:
function Init ($InputQueue){
# Create the shared thread-safe queue and fill it with the input objects
$Queue = [Collections.Queue]::Synchronized([Collections.Queue]#($InputQueue))
$QueueLength = $Queue.Count
# Do not create more runspaces than input objects
if ($MaxPipelines -gt $QueueLength) {$MaxPipelines = $QueueLength}
# Create the script to be run by each runspace
$Script = "Set-Location '$PWD'; "
$Script += {
$SplitJobQueue = $($Input)
& {
trap {continue}
while ($SplitJobQueue.Count) {$SplitJobQueue.Dequeue()}
} |
}.ToString() + $Scriptblock
# Create an array to keep track of the set of pipelines
$Pipelines = New-Object System.Collections.ArrayList
# Collect the functions and aliases to import
$ImportItems = ($Function -replace '^','Function:') +
($Alias -replace '^','Alias:') |
Get-Item | select PSPath, Definition
$stopwatch = New-Object System.Diagnostics.Stopwatch
$stopwatch.Start()
}
Thank you for your help. Because this little function might help me out a lot if it would just work.
In this section:
$Script += {
$SplitJobQueue = $($Input)
& {
trap {continue}
while ($SplitJobQueue.Count) {$SplitJobQueue.Dequeue()}
} |
}.ToString() + $Scriptblock
There doesn't appear to be any reason for that pipe to be there.

PowerShell: Manage errors with Invoke-Expression

I try to figure how to determine if a command throw with Invoke-Expression fail.
Even the variable $?, $LASTEXITCODE or the -ErrorVariable don't help me.
For example :
PS C:\> $cmd="cat c:\xxx.txt"
Call $cmd with Invoke-Expression
PS C:\> Invoke-Expression $cmd -ErrorVariable err
Get-Content : Cannot find path 'C:\xxx.txt' because it does not exist.
At line:1 char:4
+ cat <<<< c:\xxx.txt
+ CategoryInfo : ObjectNotFound: (C:\xxx.txt:String) [Get-Content], ItemNotFoundExcep
tion
+ FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetContentCommand
The $? is True
PS C:\> $?
True
The $LASTEXITCODE is 0
PS C:\> $LASTEXITCODE
0
And the $err is empty
PS C:\> $err
PS C:\>
The only way I found is to redirect STD_ERR in a file and test if this file is empty
PS C:\> Invoke-Expression $cmd 2>err.txt
PS C:\> cat err.txt
Get-Content : Cannot find path 'C:\xxx.txt' because it does not exist.
At line:1 char:4
+ cat <<<< c:\xxx.txt
+ CategoryInfo : ObjectNotFound: (C:\xxx.txt:String) [Get-Content], ItemNotFoundExcep
tion
+ FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetContentCommand
Is it the only and best way to do this ?
I was going crazy trying to make capturing the STDERR stream to a variable work. I finally solved it. There is a quirk in the invoke-expression command that makes the whole 2&>1 redirect fail, but if you omit the 1 it does the right thing.
function runDOScmd($cmd, $cmdargs)
{
# record the current ErrorActionPreference
$ep_restore = $ErrorActionPreference
# set the ErrorActionPreference
$ErrorActionPreference="SilentlyContinue"
# initialize the output vars
$errout = $stdout = ""
# After hours of tweak and run I stumbled on this solution
$null = iex "& $cmd $cmdargs 2>''" -ErrorVariable errout -OutVariable stdout
<# these are two apostrophes after the >
From what I can tell, in order to catch the stderr stream you need to try to redirect it,
the -ErrorVariable param won't get anything unless you do. It seems that powershell
intercepts the redirected stream, but it must be redirected first.
#>
# restore the ErrorActionPreference
$ErrorActionPreference=$ep_restore
# I do this because I am only interested in the message portion
# $errout is actually a full ErrorRecord object
$errrpt = ""
if($errout)
{
$errrpt = $errout[0].Exception
}
# return a 3 member arraylist with the results.
$LASTEXITCODE, $stdout, $errrpt
}
It sounds like you're trying to capture the error output of a native in a variable without also capturing stdout. If capturing stdout was acceptable, you'd use 2>&1.
Redirecting to a file might be the simplest. Using Invoke-Expression for it's -ErrorVariable parameter almost seems like a good idea, but Invoke-Expression has many problems and I usually discourage it.
Another option will look a little cumbersome, but it can be factored into a function. The idea is to merge output streams using 2>&1, but then split them again based on the type of the object. It might look like this:
function Split-Streams
{
param([Parameter(ValueFromPipeline=$true)]$InputObject)
begin
{
$stdOut = #()
$stdErr = #()
}
process
{
if ($InputObject -is [System.Management.Automation.ErrorRecord])
{
# This works well with native commands but maybe not as well
# for other commands that might write non-strings
$stdErr += $InputObject.TargetObject
}
else
{
$stdOut += $InputObject
}
}
end
{
,$stdOut
,$stdErr
}
}
$o, $e = cat.exe c:\xxx.txt 2>&1 | Split-Streams

trim input from reg query

Windows XP machine:
reg query "\\COMPUTER_NAME\HKLM\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\WinLogon" /v DefaultUserName
output of: DefaultUserName REG_SZ ajstepanik
.
Windows 7 machine
reg query "\\COMPUTER_NAME\HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI" /v LastLoggedOnUser
output of: LastLoggedOnUser REG_SZ GHS_NTDOMAIN\ajstepanik
.
.
I was wondering if it were possible to trim this down so I would be left with GHS_NTDOMAIN\ajstepanik ... or even better, if I could just get the username which in this example, is ajstepanik
The reason for pulling the name and storing it, is that I can take that and plug it into other commands.
.
.
EDIT for additional help (win7):
$reg1 = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey('LocalMachine', $tag1)
$key1 = $reg1.OpenSubKey('Microsoft\Windows\CurrentVersion\Authentication\LogonUI')
$user1 = $key1.GetValue('LastLoggedOnUser') -replace '^.*?\\'
echo $user1
returns error:
You cannot call a method on a null-valued expression.
At C:\Users\ajstepanik\Desktop\test.ps1:30 char:1
+ $user1 = $key1.GetValue('LastLoggedOnUser') -replace '^.*?\\'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
I'd drop reg.exe entirely and read the remote registry like this:
$rhost = 'COMPUTER_NAME'
$reg = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey('LocalMachine', $rhost)
$key = $reg.OpenSubKey('SOFTWARE\Microsoft\Windows NT\CurrentVersion\WinLogon')
$user = $key.GetValue('DefaultUserName') -replace '^.*?\\'
It's a cleaner approach, since GetValue already produces the actual value. You don't have to parse it out of some other string before you can do things with it.
Seems simple enough:
(reg query "\\%tag%\HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI" /v LastLoggedOnUser).split('\')[1]
It's giving you back a string. Just split it at the backslash. and take the second element.
You can use Microsoft .NET Framework types to query the registry remotely, and get an object result. Check out the Remote Registry module for PowerShell: http://archive.msdn.microsoft.com/PSRemoteRegistry
That being said, you can parse the output of your command above, like so:
$Output = reg query "\\%tag%\HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Authentication\LogonUI" /v LastLoggedOnUser
$Output -join '' -match '\w+\\\w+$';
$matches[0];
If you want to take it one step further, you can parse the domain and username via regex "named groups" like so:
$output -join '' -match '(?<domain>\w+)\\(?<username>\w+)$';
$matches.username;
$matches.domain;