SKILL.md
Windows Shell Reliability Patterns
Best practices for running commands on Windows via PowerShell and CMD.
When to Use
Use this skill when developing or debugging scripts and automation that run on Windows systems, especially when involving file paths, character encoding, or standard CLI tools.
1. Encoding & Redirection
CRITICAL: Redirection Differences Across PowerShell Versions
Older Windows PowerShell releases can rewrite native-command output in ways that break later processing. PowerShell 7.4+ preserves the byte stream when redirecting stdout, so only apply the UTF-8 conversion workaround when you are dealing with older shell behavior or a log file that is already unreadable.
| Problem | Symptom | Solution | |
|---|---|---|---|
dotnet > log.txt |
view_file fails in older Windows PowerShell |
`Get-Content log.txt | Set-Content -Encoding utf8 log_utf8.txt` |
npm run > log.txt |
Need a UTF-8 text log with errors included | `npm run ... 2>&1 | Out-File -Encoding UTF8 log.txt` |
Rule: Prefer native redirection as-is on PowerShell 7.4+, and use explicit UTF-8 conversion only when older Windows PowerShell redirection produces an unreadable log.
2. Handling Paths & Spaces
CRITICAL: Quoting
Windows paths often contain spaces.
| ❌ Wrong | ✅ Correct |
|---|---|
dotnet build src/my project/file.fsproj |
dotnet build "src/my project/file.fsproj" |
& C:\Path With Spaces\bin.exe |
& "C:\Path With Spaces\bin.exe" |
Rule: Always quote absolute and relative paths that may contain spaces.
The Call Operator (&)
In PowerShell, if an executable path starts with a quote, you MUST use the & operator.
Pattern:
& "C:\Program Files\dotnet\dotnet.exe" build ...3. Common Binary & Cmdlet Pitfalls
| Action | ❌ CMD Style | ✅ PowerShell Choice |
|---|---|---|
| Delete | del /f /q file |
Remove-Item -Force file |
| Copy | copy a b |
Copy-Item a b |
| Move | move a b |
Move-Item a b |
| Make Dir | mkdir folder |
New-Item -ItemType Directory -Path folder |
Tip: Using CLI aliases like ls, cat, and cp in PowerShell is usually fine, but using full cmdlets in scripts is more robust.
4. Dotnet CLI Reliability
Build Speed & Consistency
| Context | Command | Why |
|---|---|---|
| Fast Iteration | dotnet build --no-restore |
Skips redundant nuget restore. |
| Clean Build | dotnet build --no-incremental |
Ensures no stale artifacts. |
| Background | Start-Process dotnet -ArgumentList 'run' -RedirectStandardOutput output.txt -RedirectStandardError error.txt |
Launches the app without blocking the shell and keeps logs. |
5. Environment Variables
| Shell | Syntax |
|---|---|
| PowerShell | $env:VARIABLE_NAME |
| CMD | %VARIABLE_NAME% |
6. Long Paths
Windows has a 260-character path limit by default.
Fix: If you hit long path errors, use the extended path prefix: \\?\C:\Very\Long\Path\...
7. Troubleshooting Shell Errors
| Error | Likely Cause | Fix | |
|---|---|---|---|
The term 'xxx' is not recognized |
Path not in $env:PATH | Use absolute path or fix PATH. | |
Access to the path is denied |
File in use or permissions | Stop process or run as Admin. | |
Encoding mismatch |
Older shell redirection rewrote the output | Re-export the file as UTF-8 or capture with `2>&1 | Out-File -Encoding UTF8`. |
Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.