Error handling

Error handling is useful to decipher which line of code is not working correctly. Once the issue occurs, you can either stop, continue, break or prompt from that error. You are able to create your own error message for the script block as well. The implementation of error handling is great for logging ,etc. Powershell also does not have terminating error by default, so error handling helps a lot.

When writing try/catch scriptblock, it is recommended to output error under catch block with $.exception.message or with error variable such as $error. Admin can also adjust the $ErrorActionPreference to silently continue, break or stop script block once error is triggered.

Error actions:

The “Stop” Error Action halts script execution upon encountering an error. For instance:

“Continue” serves as the default Error Action, displaying errors while enabling the script to proceed:

With “SilentlyContinue,” error messages remain concealed, allowing the script to continue unabated:

“Ignore” behaves similarly to “SilentlyContinue” but refrains from recording errors in `$Error`:

“Inquire” prompts user interaction when an error occurs, presenting choices for action:

$ErrorActionPreference # View the current error action
$ErrorActionPreference ="stop" # To set the error action 
$ErrorActionPreference ="Break"

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Error handling format

Code in the Try block is executed, and if an error occurs, execution is transferred to the Catch block. The Finally block runs irrespective of whether an error occurred or not, making it ideal for cleanup operations

try {insert scriptblock

}catch{
     insert error message
}

try {
    # Code that might throw an error
    Get-Content -Path "C:\NonExistentFile.txt"
}
catch {
    # Handle the error
    Write-Error "An error occurred: $_"
}
finally {
    # Cleanup code
    Write-Output "End of error handling"
}

Note: -erroraction can break/continue/ignore/stop the script if an error triggers

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Example – Retrieve the content of a file and try to replace a string, if the file does not exist, output something in the catch scriptblock

try{
$file = 'C:\Sli929 Repository\tester\Test.txt'
$content = Get-Content -path $file -ErrorAction Break  #erroraction -break/stop/continue/ etc..
$content -replace ("\bBob\b",'zzz')
  }Catch{ 
    Write-output "Please double check the filepath"
         } 

Result

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Error handling format:

Another method to catch error is the “Finally” block after “Catch”

Try{}  #what the scriptblock is trying to do
Catch{} #catch error and display custom error message
Finally{} #Useful for database, api, remote  connections after its closed. It will execute even after catch is triggered. Error or no error


try{
    $file = 'C:\Sli929 Repository\tester\Test.txt'
    $content = Get-Content -path $file -ErrorAction Stop
    do {
    $value = $content | Select-String ('Bob')
    Write-Host $value
    Write-Host "Total number of string is" $value.Count 
    
    }
    while ($value.Contains('Bob'))
}
Catch {Write-Host $_.Exception.Message
        Write-Host "check scriptblock"}
Finally {Write-Host "Error check - ending script"}

Output:

Output with error: (The catch scriptblock kicks in with “Check script block” output and lists the error in white font instead of red from the $_.Exception.Message). The finally script block ends the script.