.It Li _SC_ASYNCHRONOUS_IO

Return 1 if the system supports Asynchronous I/O facilities as described in

.St -p1003.1 ,

otherwise \-1.

.It Li _SC_MAPPED_FILES

Return 1 if the system supports memory mapped files, otherwise \-1.

.It Li _SC_MEMLOCK

Return 1 if the system supports process memory locking, otherwise \-1.

.It Li _SC_MEMLOCK_RANGE

Return 1 if the system supports range memory locking, otherwise \-1.

.It Li _SC_MEMORY_PROTECTION

Return 1 if the system supports memory protection, otherwise \-1.

.It Li _SC_MESSAGE_PASSING

Return 1 if the system supports POSIX message queues, otherwise \-1.

.It Li _SC_PRIORITIZED_IO

Return 1 if the system supports POSIX prioritized I/O, otherwise \-1.

.It Li _SC_PRIORITY_SCHEDULING

Return 1 if the system supports POSIX priority scheduling, otherwise \-1.

.It Li _SC_REALTIME_SIGNALS

Return 1 if the system supports POSIX realtime signals, otherwise \-1.

.It Li _SC_SEMAPHORES

Return 1 if the system supports POSIX semaphores, otherwise \-1.

.It Li _SC_FSYNC

Return 1 if the system supports file synchronization, otherwise \-1.

.It Li _SC_RAW_SOCKETS

Return 1 if the system supports

.Dv SOCK_RAW

style raw sockets, otherwise \-1.

.It Li _SC_SHARED_MEMORY_OBJECTS

Return 1 if the system supports POSIX shared memory objects, otherwise \-1.

.It Li _SC_SYNCHRONIZED_IO

Return 1 if the system supports POSIX synchronized I/O, otherwise \-1.

.It Li _SC_TIMERS

Return 1 if the system supports POSIX timers, otherwise \-1.

.It Li _SC_IPV6

Return 1 if the system supports Internet Protocol version 6, otherwise \-1.

.It Li _SC_AIO_LISTIO_MAX

The maximum number of POSIX asynchronous I/O operations supported.

.It Li _SC_AIO_MAX

The maximum number of outstanding asynchronous I/O operations supported.

.It Li _SC_AIO_PRIO_DELTA_MAX

The maximum amount by which a process can decrease its asynchronous

I/O priority level from its own scheduling priority.

.It Li _SC_DELAYTIMER_MAX

The maximum number of timer expiration overruns permitted for each process.

.It Li _SC_MQ_OPEN_MAX

The maximum number of open POSIX message queues which a process may hold.

.It Li _SC_PAGESIZE

The system memory page size.

.It Li _SC_PAGE_SIZE

This is a synonym for

.Dv _SC_PAGESIZE .

.It Li _SC_RTSIG_MAX

The number of the highest POSIX realtime signal supported.

.It Li _SC_SEM_NSEMS_MAX

The maximum number of POSIX semaphores that a process may have.

.It Li _SC_SEM_VALUE_MAX

The maximum value that a POSIX semaphore may have.

.It Li _SC_SIGQUEUE_MAX

The maximum number of POSIX queued signals that a process may send and

have pending at receiver(s) at any given time.

.It Li _SC_TIMER_MAX

The maximum number of POSIX timers that a process may request.

.It Li _SC_NPROCESSORS_ONLN

The number of processors that are online and running in the system.

.It Li _SC_NPROCESSORS_CONF

The number of processors that are configured, but not

necessarily running, in the system.

.It Li _SC_IOV_MAX

The maximum number of iovec structures that one process may use with the

.Fn readv

and

.Fn writev

functions.

.It Li _SC_ATEXIT_MAX

The maximum number of functions that a process may register with the

.Fn atexit

function.