Powershell：别名和Function有什么区别？

Question

Im setting up my powershell profile to create aliases of commonly used commands. On Microsoft's documentation it says, if I want to make an alias for a command with parameters, I should make the value of the alias a Function that does that. . However, when I type the name of the function in the command line it works just as well as an alias.

In other words, in the above picture, if I typed CD32 it would behave the same as if I typed Go in the command line

So my question is: Why do I use aliases pointing to functions when I could just have a function? Are there feature differences between the two?

Answer 1

• 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 ); eg, 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 .

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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 (eg, Invoke-Foo ), and you also want a short name for interactive convenience (eg, foo ), you'll have to also define an alias for that function with that short name (eg, Set-Alias foo Invoke-Foo ).