sched_rr_get_interval writes into the timespec structure pointed to by tp the round robin time quantum for the process identified by pid. If pid is zero, the time quantum for the calling process is written into *tp. The identified process should be running under the SCHED_RR scheduling policy.
The round robin time quantum value is not alterable under Linux 1.3.81.
POSIX systems on which sched_rr_get_interval is available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.
On success, sched_rr_get_interval returns 0. On error, -1 is returned, and errno is set appropriately.