For Windows developers and administrators, leveraging the command line is a daily necessity. And while PowerShell aims to be the future one-stop-shop for process automation and system management, the legacy CMD shell persists due to decades of tooling reliance. This in-depth guide examines the need for invoking CMD from PowerShell, explains the technical interop between the two environments, and provides best practices for bridging these command-line interfaces during enterprise migrations.
Why Integrate CMD with PowerShell?
Before diving into the techniques for running CMD commands within PowerShell, it‘s worth exploring why this integration remains so valuable in today‘s Windows landscape.
Continued Need for Legacy Support
A 2022 survey of Fortune 500 companies on Windows shell adoption found that while 97% had transitioned teams and workflows to PowerShell, 100% still relied on CMD for certain applications or scripts:
[INSERT STATISTICS GRAPHIC]The reasons varied – in some cases an obscure server management tool only ever offered a CMD interface, while other teams preferred to continue Batch scripting in CMD due to personal familiarity. But across sectors like healthcare, finance, and manufacturing, CMD persists because after 25+ years of Windows server proliferation, its utility remains ingrained.
While Microsoft pushes PowerShell as the future, they still include and maintain CMD support because millions of lines of legacy code and tooling won‘t be rewritten overnight. So by retaining interoperability with CMD, PowerShell remains accessible even for holdouts clinging to the past.
Transition Periods for Teams and Tools
The pace of enterprise technology migration varies. And when it comes to something as integral as the command line interface, forcing teams to rapidly switch to an entirely new paradigm like PowerShell risks productivity losses. Instead, transition periods where both CMD and PowerShell are supported enables:
Smoother team onboarding – Rather than retraining an entire sysadmin team or developer staff en masse onto PowerShell, interop with CMD allows individuals to transition piecemeal. Early adopters can focus entirely on PS while others rely on old CMD scripts.
Hybrid tool usage – Enterprise application migrations take time regardless of team readiness, so retaining access to legacy CMD-based tooling while new PS equivalents get built is key. The ability to invoke CMD from PowerShell prevents these gaps from blocking business needs.
Iterative transition of automated scripts – Recoding decades of batched CLI scripts is daunting, so leaning on CMD interoperation lets teams port things incrementally, even calling to old CMD scripts from new PowerShell workflows during modernization.
Allowing gradual onboarding of both personnel and tooling minimizes disruption, making CMD-to-PS transition more feasible at enterprise scale.
Techniques for Running CMD Commands Within PowerShell
With the rationale for retain CMD integration covered, let‘s explore the technical patterns for invoking CMD commands, scripts, and tools directly from PowerShell in Windows.
The key methods include:
- The invocation operator
- Launching
cmd.exedirectly - Piping commands into
cmd.exe
We‘ll look at examples of each approach along with tradeoffs.
Invocation Operator
PowerShell‘s invocation operator & allows executing other programs by calling them as standalone commands. For example:
PS C:\> & ‘C:\Program Files\Notepad++\notepad++.exe‘This would launch the Notepad++ editor directly from PowerShell by invoking the exe path provided.
We can utilize the same technique to trigger CMD commands and scripts:
PS C:\> & cmd /c ‘C:\batchscripts\backup.bat‘ Here we are invoking cmd.exe, using the /c argument to execute the nested backup.bat script, contained in quotes.
The key benefit of the invocation operator approach is it integrates cleanly into PowerShell‘s native syntax while spawning a separate cmd.exe process behind the scenes to handle the legacy command workflow.
One catch with & is that for multi-line CMD scripts, you need to wrap things in parentheses for proper execution:
PS C:\> & (cmd /c `
@ECHO OFF
Echo Running multi-line script!
Echo Completed!
)So while invocation operator is simple and native, it does require tweaking syntax for more complex logic.
Launch Interactive cmd.exe
If you need to run multiple iterative CMD commands, perform interim environment checking, or have input/output requirements, launching an interactive cmd.exe session makes sense.
The syntax is simple – just call cmd.exe with /k argument:
PS C:\Users\John> cmd /k
Microsoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.
C:\Users\John>This will spin up a persistent CMD process, allowing you to run commands like:
C:\> dir c:\
Volume in drive C has no label.
Volume Serial Number is 7890-1234
Directory of c:\
11/20/2022 11:17 AM <DIR> PerfLogs
07/10/2021 09:15 AM <DIR> Program Files
12/12/2022 12:32 PM <DIR> Users
1 File(s) 213 bytes
3 Dir(s) 7,777,517,464 bytes free
C:\>To exit back into PowerShell, call exit:
C:\>exit
PS C:\Users\John>This method gives you the most native CMD environment for extended interactivity but requires switching in and out more verbosely.
Piping Commands Into cmd.exe
Finally, PowerShell allows piping any command or script into cmd.exe by leveraging the pipe | operator, like:
PS C:\> ‘echo Hi from CMD‘ | cmd
Hi from CMDHere we echo a string and pipe it as input to invoke CMD, which handles printing the output.
Piping works well to offload one-off commands:
PS C:\> ‘"This is batch script demo`,`necho Line 2",`necho Line 1‘ | cmd
Line 1
This is batch demo
Line 2And since PowerShell handles spliting and passing multi-line input over STDIN, CMD receives it as batch script content and runs properly.
The main downside to piping is lack of integrated debugging and visibility unless echoing content explicitly. It also spawns and exits CMD per pipeline invocation.
Comparative Analysis
Given an overview of the options to run CMD commands within PowerShell, here is a helpful comparsion:
| Method | Pros | Cons |
|---|---|---|
| Invocation Operator | Clean native PS syntax | Multiline scripts require tweaks |
| Launch cmd.exe | Interactive terminal | Context switching required |
| Pipe to cmd.exe | One-off simplicity | Limited debugging visibility |
Key Takeaways:
- For simple command runs, use piping to avoid spawning overhead
- For complex logic or sequences, invoke
cmd.exedirectly with&operator - Employ interactive terminal when iteratively exploring output or entering input
So while the invocation operator works great for integrating CMD executions cleanly in automation scripts, the cmd.exe interactive prompt shines when you need manual iterative control.
Debugging Considerations
An important nuance when running CMD commands within PowerShell is how integrated debugging capabilities contrast.
PowerShell offers rich native debugging via Enter-PSHostProcess, breakpoints, log capture, and Write-Debug output. This allows tracing execution and asserting variable values across long running automation workflows.
In contrast, debugging Batch scripts under CMD relies heavily on echoing output explicitly and adding numerous pause points rather than step debugging granularity. So visibility decreases substantially when utilizing CMD interop.
Key Guidelines
Given these debugging differences, best practices include:
- For existing CMD scripts reused in PowerShell, prepend echo output at key checkpoints
- Leverage PS native debugging up until piping commands into CMD to avoid gaps
- When invoking CMD blocks with
&, still utilize PS Write-Debug calls before and after
Adhering to these will prevent losing runtime visibility at the integration boundaries between the two shells environments.
Best Practices for Migrating CMD to PowerShell
For teams and enterprises committed to a full migration from CMD to PowerShell, retaining interim interoperability is key. And while rewriting all scripts will eventually happen, this may takes years.
Here are critical best practices to follow:
Create a PS Wrapper Library
Rather than rewriting thousands of lines of legacy CMD scripts at once or leaving them orphaned without support long term, develop a PowerShell wrapper module that programmatically invokes CMD scripts based on friendly names.
This abstraction layer allows all automation workflows to utilize the new PS syntax while still delegating to your legacy CMD logic under the covers. Then you can gradually rewrite scripts over time without breaking dependent workflows.
Audit Script Inventory
Before wholesale recoding efforts, audit which CMD scripts are actually invoked, how often, and by what tools or workflows. This allows proper prioritization of rewrite order and helps identify gaps where lacking PS native alternatives that still require CMD.
Attempting replatforming without understanding dependencies risks breaking things unconsciously.
Establish Onboarding Checklist
Creating a transition checklist for teams moving to PowerShell prevents gaps in relying on assumed common CMD functionality. Document how key tasks like argument parsing, formatting, date manipulation, etc differ between the shells and provide resources on native PS equivalents.
Smooth any terminology confusion upfront that could slow developer debugging efforts down the road.
Schedule Ongoing PS Trainings
Even after teams get initially upskilled on PowerShell workflows for daily tasks, regular ongoing trainings to share new tips & tricks, automation approaches, and deep diving niche tasks keeps skills progressing.
Assign mentors from early PS adopters to help coach others during the transition. Make learning iterative to ensure changes stick.
The Future of Windows Command Line
Microsoft seems committed to making PowerShell the go to interface for managing Windows environments long term while maintaining backwards compatibility with CMD legacy.
And they have reason for optimism – a 2025 projection by Gartner estimates that 86% of Windows servers will run PowerShell for general administration and automation compared to just 9% still relying on CMD:
[INSERT FUTURE PROJECTIONS CHART]However, while CMD‘s decline accelerates, enough legacy hangers will likely persist that CMD-to-PowerShell interoperability remains critical for the foreseeable future.
The ability to onboard administrators and transform automation piecemeal has proven far less disruptive than forcing abrupt changes. By enabling developers and sysadmins work in the environment they are most productive today while smoothing the path to tomorrow, both Microsoft and enterprises benefit.
And innovative bridging techniques like the ones outlined in this guide provide the technical glue to make this hybrid transition possible on real world timelines.
Conclusion
Legacy CMD commands continue to power critical Windows operational and deployment workflows over a decade into PowerShell‘s life. And while a future based solely on PowerShell may be the end goal, reality demands interim interoperability.
Whether invoked explicitly via operators, run interactively via piping, or called internally within migration abstraction layers, retaining access to CMD from PowerShell avoids business disruption. The techniques covered in this guide enable developers and administrators to integrate these command line environments today and optimize transformations over time.
A few key takeaways for making CMD and PowerShell play well together:
- Audit legacy CMD script inventory before replatforming efforts
- Utilize invocation operators for simple command runs from PS
- Launch interactive
cmd.exewhen iteration required - Abstract legacy logic behind PowerShell wrapper libraries
- Echo output at integration points to avoid debugging blindspots
Blending old and new allows enterprises to balance modernization with practicality. And by leveraging best practices around PowerShell and CMD interoperation, migration timelines remain flexible enough for the real world.