I'm trying to understand how the below works in Linux:

What happens when you fork() from one of the created threads?

• what happens to other threads?

What happens when you fork() from the main thread (the thread/process calling fork)?

• What happens if the main thread/process has multiple threads running? Does all the threads get duplicated too?

In both the above cases, where is the SIGCHLD signal sent to when the forked child process terminates?