You have assumptions you may not realize that you have.
When a parent creates a child
1. if the child "stays" as a child it can communicate to the parent via pipes, shared memory - ipc in general is possible. Sometimes the child stdout is the parent's same stdout (shared) with the parent. There no requirement that it be done one way or another. The parent should call wait() on the child process and then take correct action depending on the return from the child (exit()).
2. The child calls setsid() and becomes the head of its very own process. It can still talk to the parent if it is coded to do that, but when the process ends, the parent has gone on to do other things and had not called wait() on the child.
3. a daemon is a special version of #2. The child turns off connections to stdin, stdout, stderr. These processes are often called services. Normally they do not engage in IPC with the parent.
4. Sometimes a child can be #1, #2, or #3 but it uses signals to/from the parent to interoperate.
Shells mostly use #1 - you type the
ls command, it does it's thing, writes to stdout, then calls exit. The status of the child is available to the parent shell in the
$? variable.
I've simplified this for understanding. Someone else may not feel my choices were the best. In any event - You should really consider learning what
https://www.tldp.org/LDP/tlk/ipc/ipc.html has to say. And learn it reasonably well.
