How and why did I start a blog? (plus error type in try-catch)
Well, I’m heavily influenced by Doug Finke, Jeff Hicks, Mike F Robbins, Andrew Pla and many others, and those learned experts often mention that a personal blog is a great way to help you remember your own tips and tricks during your learning journey with anything that you learn. Just write a blog for yourself, so that is my inspiration.
How to identify the right catch specification for your try-catch blocks.
try {
# Generate the error
Get-Command not_a_command -ErrorAction Stop
} catch {
$error[0] | Select Exception
$error[0] | % Exception
$error[0] | % CategoryInfo
$error[0] | % CategoryInfo | % Reason
$error[0].Exception.GetType().FullName # top tip
$error[0] | % FullyQualifiedErrorId
}
The code in the catch block shows various ways to inspect the error. You see more, pipe from $error[0] to Get-Member like this: $error[0] | Get-Member
What is $error[0] ?
$error[0] an automatic variable. For more details, check the about_automatic_variables documentation
Top tip
I show you $error[0].Exception.GetType().FullName.
The Get-Command not_a_command that I use above generates an ErrorRecord, because the term ‘not_a_command’ is not recognized as the name of a cmdlet, function, or operable program.
The ErrorRecord exception type is “CommandNotFoundException”, but to catch that exception by type it is not enough to use “CommandNotFoundException”.
So, what should you use?
That answer can be found by reading the System.RuntimeType FullName for the Exception.
This value is provided by $error[0].Exception.GetType().FullName and it’s value is System.Management.Automation.CommandNotFoundException
Here is an example of how you can use that type information to Catch that exception.
try {
# Generate the error
Get-Command not_a_command -ErrorAction Stop
}
catch [System.Management.Automation.CommandNotFoundException] {
"A CommandNotFoundException was thrown"
}
Play around with the code above, see how commenting out -ErrorAction Stop denies the explicit catch handling.