How do you debug PowerShell scripts?

1 Set breakpoints

Breakpoints are points in your code where you want the execution to pause and let you inspect the variables, output, and logic. You can set breakpoints in PowerShell using the Set-PSBreakpoint cmdlet, which takes parameters such as -Line, -Variable, -Command, and -Script. For example, to set a breakpoint on line 10 of a script called test.ps1, you would run: Set-PSBreakpoint -Script test.ps1 -Line 10 You can also set conditional breakpoints that only trigger when a certain expression is true. For example, to set a breakpoint on line 10 of test.ps1 only when the variable $x is greater than 10, you would run: Set-PSBreakpoint -Script test.ps1 -Line 10 -Condition {$x -gt 10} To view the breakpoints you have set, use the Get-PSBreakpoint cmdlet. To remove breakpoints, use the Remove-PSBreakpoint cmdlet.

2 Use the debugger

Once you have set breakpoints, you can use the PowerShell debugger to step through your code and examine its behavior. This mode of the PowerShell console gives you access to special commands and features, which you can enter by running your script with the -Debug parameter or pressing F5 in the PowerShell Integrated Scripting Environment (ISE). When the debugger hits a breakpoint, it will display the current line of code and prompt you for a command. You can use commands like 'Step-Into' (s) to execute the current line of code and pause at the next line or function call; 'Step-Over' (v) to execute the current line of code and pause at the next line in the same scope; 'Step-Out' (o) to execute the rest of the current function and pause at the next line in the caller function; 'Continue' (c) to resume execution until the next breakpoint or end of script; 'Quit' (q) to exit the debugger and stop script; 'Get-PSCallStack' (k) to show the current call stack; 'List' (l) to show source code around the current line; or 'Help' (h) for help information about debugger commands. Additionally, you can use any PowerShell cmdlet or expression in this prompt to evaluate variables, parameters, or output.

3 Use Write-Debug and Write-Verbose

Another way to debug PowerShell scripts is to use the Write-Debug and Write-Verbose cmdlets. These cmdlets allow you to write messages to the console that can help you track the flow and state of your code. Write-Debug writes messages that are only displayed when the -Debug parameter is used, while Write-Verbose writes messages that are only displayed when the -Verbose parameter is used. For example, you can add the following lines to your script to write debug and verbose messages:

Write-Debug "Starting the script"
Write-Verbose "The value of x is $x"        

To see the messages, you need to run your script with the appropriate parameters, such as: .\test.ps1 -Debug -Verbose You can also use the $DebugPreference and $VerbosePreference variables to control the behavior of Write-Debug and Write-Verbose. For example, you can set them to "Continue" to always display the messages, or to "SilentlyContinue" to suppress them.

Debugging PowerShell scripts can be a challenging but rewarding task. By using breakpoints, the debugger, and Write-Debug and Write-Verbose, you can find and fix errors and bugs in your code and improve its quality and performance.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?