-.It NOTE_TRACK
-Follow a process across
-.Fn fork
-calls. The parent process will return with NOTE_TRACK set in the
-.Va fflags
-field, while the child process will return with NOTE_CHILD set in
-.Va fflags
-and the parent PID in
-.Va data .
-.It NOTE_TRACKERR
-This flag is returned if the system was unable to attach an event to
-the child process, usually due to resource limitations.