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Published on: 2019-02-05

Powershell Best Practices

Estimated time to read: 3 minutes

An aggregation of various recommendations

  • Start script with a standard set of comments such as name, date, purpose, etc.
  • Use #Requires to set minimum PS version required, modules, etc.
  • Use Set-StrictMode -Version Latest to prevent the use of unitialised variables (similar to Option Explicit in VBScript)
  • Use simple but meaningful variable names. Camel Case is "the best practice"
  • Use code signing
  • Don't use aliases, use full cmdlet anmes and named parameters
  • Don't use backticks
  • Filter left, format right
  • Add .exe for any external commands/apps being called
  • Use structured error handling (with Try, Catch, Finally/Trap)
  • Use cmdletBinding and add support for -Whatif, Verbose, Debug
  • Use Advanced Functions
  • Use Verb-Noun naming for functions, etc. For the Verbs, use a standard verb (Get-Verb lists these)
  • Use standard parameter naming (ie. ComputerName is good, Machine or Server is bad) and set to a default value if relevant/possible (ie. $ComputerName = $ENV:ComputerName)
  • A function should do thing
  • A function should return an object or an array of objects, not formatted text
  • Avoid using the Return keyword. Functions automatically return output to the calling process via the pipeline
  • Use write-output over write-host (write-host only writes to the host, not the pipeline)
  • Use comment-based help

  • Use Test-Connection to check if a target is online

  • Use full cmdlet names

  • Use named parameters
  • Avoid write-host
  • Use CIM cmdlet (not WMI cmdlet)
  • For Verb-Noun, use a singular form
  • Use approved verbs
  • Use Whatif/Confirm parameters
  • Use custom folding regions
  • Use Set-StrictMode
  • Avoid Out-Null
  • Specify the extension for applications (ie. .exe)
  • Execute scripts with -NoProfile Parameter
  • Check parameters with PSBoundParameters (PSBoundParamters is a hashtable of parameters passed to a script of function)

  • Use #Requires

  • Use approved verbs for commands (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/approved-verbs-for-windows-powershell-commands?view=powershell-7.1)

  • Don’t use special characters in cmdlet names (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#cmdlet-names-characters-that-cannot-be-used-rd02)
  • Don’t use common parameter names for your parameters (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/common-parameter-names?view=powershell-7.1)
  • Support “Confirm” reqests. If the cmdlet modifies the system, it should allow the use of confirmation (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.* 1#support-confirmation-requests-rd04)
  • Support “Force” parameter for interactive sessions (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#support-force-parameter-for-interactive-sessions-rd05)
  • Document the objects that are written to the pipeline/outputted by your cmdlet (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#document-output-objects-rd06)
  • Derive from the Cmdlet or PSCmdlet Classes (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#derive-from-the-cmdlet-or-pscmdlet-classes-rc01)
  • Specify the Cmdlet Attribute (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#specify-the-cmdlet-attribute-rc02)
  • Override an Input Processing Method (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#override-an-input-processing-method-rc03)
  • Specify the OutputType Attribute (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#specify-the-outputtype-attribute-rc04)
  • Do Not Retain Handles to Output Objects (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#do-not-retain-handles-to-output-objects-rc05)
  • Handle Errors Robustly (https://docs.microsoft.com/en-us/powershell/scripting/developer/cmdlet/required-development-guidelines?view=powershell-7.1#handle-errors-robustly-rc06)

References

  • https://blogs.technet.microsoft.com/pstips/2014/06/17/powershell-scripting-best-practices/
  • http://powershell-guru.com/best-practices/