How do languages ​​running on a VM write to the console?

Question

Operating Systems

I wanted to know how console output works under the hood. I know that data is simply written to stdout, but two questions arise here: 1. How do programs find this very stdout? 2. How do they write data to it?

I would like to know how it works exactly in the case of languages ​​like Java or C #, because with low-level languages ​​everything is more or less clear (I heard that in unix-like systems this stdout is in / dev / fd / 1 and write data into it using the POSIX API).

Answer 1

stdout is just a handle that opens the console.
For each console program, three descriptors with numbers 0, 1, 2 (stdin, stdout, stderr) are opened, where they can write.
/dev/fd/1
No, fd is just a file descriptor/1
, the correct path would be /proc/process_id/fd/1
i.e. each process has its own stdout.
Well, more. It doesn't matter what language. This is about the operating system architecture, not the language.

Answer 2

how it works exactly in the case of languages ​​like Java or C#

This is hidden in library functions and the programmer may not think about how it works. You call the standard output function and it does all the work. Examples:
https://ru.wikipedia.org/wiki/Printf
https://prog-cpp.ru/cpp-std/

you can write data to it using the POSIX API

It may be possible. But in fact, everyone uses the same library functions.