Скачать или смотреть How to Write-Output a PowerShell Process Object's ExitCode

Learn how to properly output the ExitCode from a PowerShell process object using simple techniques. Find solutions to your scripting problems in PowerShell.
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How to Write-Output a PowerShell Process Object's ExitCode

Using PowerShell to execute processes and capture their ExitCodes can sometimes lead to confusing error messages. Many users find themselves stuck when trying to output the ExitCode from their scripts. If you've ever faced the challenge of seeing errors while trying to print the ExitCode, you’re not alone. In this guide, we'll diagnose the problem and explore the elegant solution.

Understanding the Problem

When executing a command through PowerShell with Start-Process, you might attempt to access properties of the resulting process. For instance, when you try to retrieve the ExitCode of a process, it's crucial to ensure you're handling the data types correctly.

In one specific scenario, a user created a simple CMD batch file and a PowerShell script to execute it, but encountered an error message that read:

[[See Video to Reveal this Text or Code Snippet]]

The Script Overview

The PowerShell script is structured as follows:

[[See Video to Reveal this Text or Code Snippet]]

This script successfully outputs the operation of the CMD batch file, but fails on the last line because of the way the ExitCode is being referenced.

The Solution

The issue arises from PowerShell's handling of data types, particularly when properties that return "AnyType" are involved. To fix the problem, you should wrap the reference to the ExitCode property in a sub-expression. The sub-expression operator $() allows PowerShell to evaluate and properly convert the output into a format it can handle.

Corrected Code

Here's how to modify the problematic line:

[[See Video to Reveal this Text or Code Snippet]]

Why Does This Work?

By using $():

Evaluation: PowerShell executes the code within the parentheses, ensuring that it returns a value of a known type.

String Conversion: Once evaluated, the value is treated as a string, which resolves any type-related errors.

Summary

The ability to output an ExitCode in PowerShell can be straightforward if you remember this simple tip: always use a sub-expression for properties that may have ambiguous types.

By adjusting your code to use $($process.ExitCode), you ensure that PowerShell properly evaluates the value before trying to print it, leading to clear and correct output.

Here's the final output you should see:

[[See Video to Reveal this Text or Code Snippet]]

With this approach, you can confidently manage process exit codes in your PowerShell scripts and avoid common pitfalls. Happy scripting!