Notes on all the different ways that processes can be related to one another.
When one process creates another using the fork(2) system call, the former is recorded as the parent of the latter, while the latter becomes a child of the former. Significance of parent/child relationship:
A process group is a set of processex all sharing the same process group ID. This is the ID of the process that created the group.
A session is a set of processes all spawned (directly or indirectly) by the same session leader. A login shell is a session leader, and all processes it spawns in response to user commands are (at least initially) part of that same session. Any process can make itself into the leader of a new session by calling setsid(2), though it is probably a good idea to detach from its ControllingTerminal first.
4 pages link to ProcessRelationships:
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