This isn’t a Linux thing, it’s a bash thing. The <() syntax isn’t using a named pipe — it is creating an anonymous pipe. But you can replicate the same functions with named pipes.
A quick search says that Windows has support for named pipes as an IPC mechanism [1], but I’ve never used them. But this is a Windows API. I am not aware for any way to do this with plain cmd.exe. You’re not the first to ask though... [2]
Even the echo example hints, that the created pipe has a name
Well, the echo example shows that the pipe is reified at /dev/fd/63 (or /dev/fd/62 for the other pipe).
That's not a named pipe. It's a file descriptor identified by the integer that defines it, accessed under the /dev/fd listing of all file descriptors.
So, to sort of answer your questions:
How does diff know to read from those two pipes?
They're two different pipes. Diff takes two arguments. Each argument is one of the pipes.
(implied) Is there such a thing as an anonymous pipe, in any context?
Not if you consider /dev/fd/id-of-pipe to be a name. The operating system lists them all there. But usually you would use a named pipe if you wanted to be able to know the name, so that you could find it again if you didn't already have a reference to it. If you jammed your finger into my chest, I would be there, and my physical form would block the passage of your finger analogously to how an anonymous pipe nevertheless exists as an entry (two entries?) in /dev/fd. But that wouldn't tell you my name in the conventional sense, even though it would be a valid and unambiguous way to refer to me.
Comments
This isn’t a Linux thing, it’s a bash thing. The <() syntax isn’t using a named pipe — it is creating an anonymous pipe. But you can replicate the same functions with named pipes.
A quick search says that Windows has support for named pipes as an IPC mechanism [1], but I’ve never used them. But this is a Windows API. I am not aware for any way to do this with plain cmd.exe. You’re not the first to ask though... [2]
[1] https://docs.microsoft.com/en-us/windows/win32/ipc/named-pip...
[2] https://superuser.com/questions/430466/in-windows-can-i-redi...
Are you sure? How does diff know to read from those two pipes?
Even the echo example hints, that the created pipe has a name, and that name is then simply passed as the argument to the command.
Well, the echo example shows that the pipe is reified at /dev/fd/63 (or /dev/fd/62 for the other pipe).
That's not a named pipe. It's a file descriptor identified by the integer that defines it, accessed under the /dev/fd listing of all file descriptors.
So, to sort of answer your questions:
They're two different pipes. Diff takes two arguments. Each argument is one of the pipes.
Not if you consider /dev/fd/id-of-pipe to be a name. The operating system lists them all there. But usually you would use a named pipe if you wanted to be able to know the name, so that you could find it again if you didn't already have a reference to it. If you jammed your finger into my chest, I would be there, and my physical form would block the passage of your finger analogously to how an anonymous pipe nevertheless exists as an entry (two entries?) in /dev/fd. But that wouldn't tell you my name in the conventional sense, even though it would be a valid and unambiguous way to refer to me.