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Using tab-completion in the shell

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PowerShell provides completions on input to provide hints, enable discovery, and speed up input entry. Command names, parameter names, argument values and file paths can all be completed by pressing the Tab key.

The Tab key is the default key binding on Windows. PSReadLine also provides a MenuComplete function that's bound to Ctrl+Space. The MenuComplete function displays a list of matching completions below the command line.

These keybindings can be changed using PSReadLine cmdlets or the application that's hosting PowerShell. Keybindings can be different on non-Windows platforms. For more information, see about_PSReadLine_Functions.

Built-in tab completion features

PowerShell has enabled tab completion for many aspects of the command line experience.

Filename completion

To fill in a filename or path from the available choices automatically, type part of the name and press the Tab key. PowerShell automatically expands the name to the first match that it finds. Pressing the Tab key again cycles through all the available choices with each key press.

Command and parameter name completion

The tab expansion of cmdlet names is slightly different. To use tab expansion on a cmdlet name, type the entire first part of the name (the verb) and the hyphen that follows it. You can fill in more of the name for a partial match. For example, if you type get-co and then press the Tab key, PowerShell automatically expands this to the Get-Command cmdlet (notice that it also changes the case of letters to their standard form). If you press Tab key again, PowerShell replaces this with the only other matching cmdlet name, Get-Content. Tab completion also works to resolve PowerShell aliases and native executables.

The following graphic shows examples of tab and menu completion.

Tab and menu completion examples

Other tab completion enhancements

Each new version of PowerShell includes improvements to tab completion that fix bugs and improve usability.

PowerShell 7.0

  • Tab completion resolves variable assignments that are enums or are type constrained
  • Tab completion expands abbreviated cmdlets and functions. For example, i-psdf<tab> returns Import-PowerShellDataFile

PowerShell 7.2

  • Fix tab completion for unlocalized about* topics
  • Fix splatting being treated as positional parameter in completions
  • Add completions for Comment-based Help keywords
  • Add completion for #requires statements
  • Add tab completion for View parameter of Format-* cmdlets
  • Add support for class-based argument completers

PowerShell 7.3

  • Fix tab completion within the script block specified for the ValidateScriptAttribute
  • Added tab completion for loop labels after break and continue
  • Improve Hashtable completion in multiple scenarios
    • Parameter splatting
    • Arguments parameter for Invoke-CimMethod
    • FilterHashtable parameter for Get-WinEvent
    • Property parameter for the CIM cmdlets
    • Removes duplicates from member completion scenarios
  • Support forward slashes in network share (UNC path) completion
  • Improve member auto completion
  • Prioritize ValidateSet completions over enums for parameters
  • Add type inference support for generic methods with type parameters
  • Improve type inference and completions
    • Allows methods to be shown in completion results for ForEach-Object -MemberName
    • Prevents completion on expressions that return void like ([void](""))
    • Allows non-default Class constructors to show up when class completion is based on the AST

Other ways to enhance tab completion of command parameters

Built-in tab expansion is controlled by the internal function TabExpansion or TabExpansion2. It's possible to create functions or modules that replace the default behavior of these functions. You can find examples in the PowerShell Gallery by searching for the TabExpansion keyword.

Using the ValidateSet or ArgumentCompletions attributes with parameters

The ArgumentCompletions attribute allows you to add tab completion values to a specific parameter. The ArgumentCompletions attribute is similar to ValidateSet. Both attributes takes a list of values to be presented when the user presses Tab after the parameter name. However, unlike ValidateSet, the values aren't validated.

For more information, see:

Using the ArgumentCompleter attribute or Register-ArgumentCompleter with parameters

An argument completer is a script block or function that provides dynamic tab completion for parameter values.

The ArgumentCompleter attribute allows you to register a function that provides tab completion values to for the parameter. The argument completer function must be available to the function containing the parameter with the ArgumentCompleter attribute. Usually, the function is defined in the same script or module.

For more information, see ArgumentCompleter.

The Register-ArgumentCompleter cmdlet registers a script block as an argument completer function at run time for any command you specify. This allows you to define argument completers outside of the script or module or for native commands. For more information, see Register-ArgumentCompleter.

Predictive IntelliSense in PSReadLine

PSReadLine 2.1.0 introduced the Predictive IntelliSense feature. Predictive IntelliSense provides suggestions for full commands based on items from your PSReadLine history.

PSReadLine 2.2.2 extends the power of Predictive IntelliSense by adding support for plug-in modules that use advanced logic to provide suggestions for full commands. The Az.Tools.Predictor module was the first plug-in for Predictive IntelliSense. It uses Machine Learning to predict what Azure PowerShell command you want to run and the parameters you want to use.

For more information, see Using predictors.