Programmatically check if a process is being run in the background

Question

2 questions:

1) Is there any Linux/Posix API to know if a process has been invoked as a background process?

linux> myprogram &

Answer 1

A process is in the background if its parent shell process isn't suspended (waiting), which you can check through the PID.

To put a process in the background (detach it completely from the shell at runtime), you use the daemon(3) function.