Powershell: What’s the difference between Alias and Function?

by

  • An alias in PowerShell allows you to define an alternative name for another command.

    • Unlike in POSIX-compatible shells such as bash, you cannot include pass-through arguments in its definition – you need a function for that.

    • The typical use case is to define a short alternative name for convenience of interactive invocation; for instance, PowerShell has a built in gc alias for its Get-Content cmdlet. PowerShell even recommends a naming convention for aliases, based on official short alias prefixes for its approved verbs, such as the g for the Get verb in the given example.

    • Another, problematic use is to define aliases named for a different shell’s commands; for instance, PowerShell has a built in dir alias for its Get-ChildItem, named for cmd.exe‘s (Command Prompt’s) internal dir command. While that may be somewhat helpful while transitioning from cmd.exe, it only works in very simple invocations, and quickly becomes problematic due to PowerShell’s fundamentally different command-line syntax and differing parameter names.

    • Another, unproblematic use is to define an alias for an external executable whose directory isn’t listed in the path ($env:PATH); e.g., if you want to execute c:\path\to\foo.exe as just foo without having to add c:\path\to to $env:PATH, you can use Set-Alias foo c:\path\to\foo.exe.

    • Unlike in POSIX-compatible shells such as bash, aliases are (invariably) usable in scripts (*.ps1 files), but their use in scripts is discouraged in the interest of robustness and long-term stability.

  • A function, as is to be expected, is a named unit of code that can accept arguments and can perform arbitrary operations.

    • A function is what you need to use if you want to wrap existing commands, by hard-coding pass-through arguments and / or providing custom logic around the invocation of the wrapped command – see this answer.

As for whether it makes sense to define an alias for a function, if implementation of your command requires a function (due to requiring more than just a simple name mapping):

  • If all you need is one (short) name for your command, you can define your function directly with that name – no alias needed.

  • By contrast, if your function needs a long name, especially an advanced (cmdlet-like) function that adheres to PowerShell’s verb-noun naming convention (e.g., Invoke-Foo), and you also want a short name for interactive convenience (e.g., foo), you’ll have to also define an alias for that function with that short name (e.g., Set-Alias foo Invoke-Foo).

More Related Contents:

  1. How to run a PowerShell script without displaying a window?
  2. How to run a PowerShell script
  3. How to run a PowerShell script within a Windows batch file
  4. How do I get the current username in Windows PowerShell?
  5. PowerShell: Setting an environment variable for a single command only
  6. How to do password-less login using plink? [closed]
  7. How can you find and replace text in a file using the Windows command-line environment?
  8. Using UTF-8 Encoding (CHCP 65001) in Command Prompt / Windows Powershell (Windows 10)
  9. Aliases in Windows command prompt
  10. How to run a PowerShell script from a batch file
  11. Can Windows’ built-in ZIP compression be scripted?
  12. $LastExitCode=0, but $?=False in PowerShell. Redirecting stderr to stdout gives NativeCommandError
  13. Is there replacement for cat on Windows
  14. Windows batch file file download from a URL
  15. Setting a windows batch file variable to the day of the week
  16. Unix tail equivalent command in Windows Powershell
  17. How to create batch file in Windows using “start” with a path and command with spaces
  18. Capture program stdout and stderr to separate variables
  19. Convert a small PS script into a long line in a .BATch file
  20. Running cURL on 64 bit Windows
  21. How does PowerShell treat “.” in paths?
  22. How do you successfully change execution policy and enable execution of PowerShell scripts
  23. Cannot remove item, The Directory is not empty
  24. PowerShell stripping double quotes from command line arguments
  25. Get Folder Size from Windows Command Line
  26. Start a detached background process in PowerShell
  27. Windows Script Host Error: Invalid character – Code:800A03F6 – Source: Microsoft JScript compilation error
  28. What’s the environment variable for the path to the desktop?
  29. powershell : changing the culture of current session
  30. IE Enable/Disable Proxy Settings via Registry

Leave a Comment