How to transfer a large array of data between processes?

Question

C++ / C#

Prompt a library/method with which it is possible to exchange data between processes (under different users) for Linux.
The program will execute functionality: run a child process under another user, and transfer files there. In this case, the child process may have an error, which the process will report to the parent. More than one transfer can occur in parallel.
I have a file stream, if it were to be passed directly to the child process, so that it would not eat a lot of resources and be pretty fast.
What tell me?

Answer 1

You can use NamedPipeClientStream and NamedPipeServerStream - this is probably the fastest/lightweight way.

Answer 2

Use sockets. Universal way for all OS.
And in addition, Linux has an IPC socket
https://ru.wikipedia.org/wiki/Unix_domain_socket