[MrQuincle]

Can you explain me a bit the difference if you mind (I don't know much about Windows).

In Linux/Unix I can also pipe audio to /dev/audio for example. And image processing through a sequence of steps by pipes is quite often done. Are these objects coming with default metaparameters to make piping easier? Or are there other things implemented that might be cool?

[tatterdemalion]

I have never used PowerShell, so I don't know a lot about the details. But PowerShell pipes .NET objects from one command to the next, which are not just bytestreams but are objects, with methods and such. It's fundamentally different.

In UNIX, you have bytes, and the underlying system doesn't know what they represent. Most tools assume they're ASCII or UTF-8 (or whatever) encoded text, but that's all they agree on. In practice, you're working almost always working with structured data - tables or lists or mappings - but you have to remember that for the output of this program, you want to cut on '=' and take -f4, and first you need to pipe it through head and tail to clean up some junk output[1], and this other thing for that program, and whatever.

[1] This is a way to get the `time` field from the output of `ping`.

[integraton]

> It's fundamentally different.

That's because the object pipeline is functionally analogous to function chaining within a single runtime like in Python or Ruby, not streaming data between arbitrary executables like in Unix pipelines.

This would be a lot clearer if PowerShell advocates compared it to things that it's actually functionally analogous to, but they are trying to position it as a Unix shell competitor.

[useerup]

> That's because the object pipeline is functionally analogous to function chaining within a single runtime like in Python or Ruby

No it is not. See my response below.

[integraton]

PowerShell's object pipeline only exists within the PowerShell/.NET runtime and is functionally analogous to method/function chaining in languages like JavaScript and Ruby. The object pipeline does not exist outside of the PowerShell/.NET runtime.

Pipelines in Unix shells use OS-level functionality to connect standard streams of data, often encoded as text, between arbitrary executables written in any language.

The reason this is confusing is because one of the main tactics used in PowerShell promotion is to disingenuously compare PowerShell's "object pipeline" to Unix pipelines in order to try to make it appear to be more novel than it is, when they should be comparing it to what it's functionally equivalent to, which is function chaining within a single runtime.

[useerup]

> which is function chaining within a single runtime

If PowerShells pipelines are merely equivalent to function chaining, then you should have no problem replicating the following very simple pipeline with function chaining in Ruby, Python or JavaScript:

    cat log.txt -wait | sls "error"

In case you need an explanation for what it is doing: It continously monitors the log.txt file for new lines, and selects those that contains the substring "error".

But I am curious: Why is it important whether the pipelines could be implemented using function chaining or not? PowerShell is a shell where I interact with the system through commands. Yes - those commands are not the typical Unix executables - but they act as commands within the shell

Is your problem that it is not a Unix shell? You could equally well say that Unix shell pipelines are just processes connected by file descriptors. That is factually correct but does not represent the true utility of pipelines.

PowerShell pipelines are not file descriptors. PowerShell commands do not execute in separate processes. But PowerShell commands are versatile and can be combined in a way analogous to Unix shell pipelines where the output of one command is consumed and acted upon by the next command.

The object of a operating system command line shell is to expose the operating system features to the user of the shell. Why does it matter whether it uses Unix file descriptors. Even if PowerShell pipelines were equivalent to "just" chained functions, why does it matter?

I get the point that you need the .NET runtime to run PowerShell, because it is implemented using .NET. At what point do we consider a runtime part of the operating system. When it is intrinsically distributed with the operating system and cannot be uninstalled?

[kbenson]

To underscore how the idea of a UNIX shell working on file descriptors between executables isn't really important, it's worth nothing that bash allows piping between it's built in commands/keywords. Not only can you pipe the aggregates output from a for, if or while construct, you can pipe the output of bash builtins such as bg, fg and disown.

[kazinator]

"objects" means data structures. It means you can have some structure with fields, or list or array or whatever as the output of one command, and input of the next one, so the next one doesn't have to do character-level parsing.

Of course, this kind of piping is present in nice languages that precede the PowerShell.

A one page Lisp macro will give you a left-to-right syntactic sugar for filtering. Clojure has a threading operator, Ruby has cascades of dots: object.{ blah }.foo().bar() ... and so on.

[tatterdemalion]

This is not what "objects" means (objects have methods), and .NET objects are a much higher level abstraction than structured data.