# posixoptions

## NAME



           posixoptions - optional parts of the POSIX standard
    


## DESCRIPTION



           The POSIX standard (the information below is from POSIX.1-2001)
           describes a set of behaviors and interfaces for a compliant
           system.  However, many interfaces are optional and there are
           feature test macros to test the availability of interfaces at
           compile time, and functions sysconf(3), fpathconf(3), pathconf(3),
           confstr(3) to do this at run time.  From shell scripts one can use
           **getconf**(1).  For more detail, see sysconf(3).
    
           We give the name of the POSIX abbreviation, the option, the name
           of the sysconf(3) parameter used to inquire about the option, and
           possibly a very short description.  Much more precise detail can
           be found in the POSIX standard itself, versions of which can
           nowadays be accessed freely on the web.
    
       **ADV - _POSIX_ADVISORY_INFO - _SC_ADVISORY_INFO**
           The following advisory functions are present:
    
               _posix_fadvise_()
               _posix_fallocate_()
               _posix_memalign_()
               _posix_madvise_()
    
       **AIO - _POSIX_ASYNCHRONOUS_IO - _SC_ASYNCHRONOUS_IO**
           The header _< aio.h>_ is present.  The following functions are
           present:
    
               _aio_cancel_()
               _aio_error_()
               _aio_fsync_()
               _aio_read_()
               _aio_return_()
               _aio_suspend_()
               _aio_write_()
               _lio_listio_()
    
       **BAR - _POSIX_BARRIERS - _SC_BARRIERS**
           This option implies the **_POSIX_THREADS** and
           **_POSIX_THREAD_SAFE_FUNCTIONS** options.  The following functions are
           present:
    
               _pthread_barrier_destroy_()
               _pthread_barrier_init_()
               _pthread_barrier_wait_()
               _pthread_barrierattr_destroy_()
               _pthread_barrierattr_init_()
    
       **--- - POSIX_CHOWN_RESTRICTED**
           If this option is in effect (as it always is under POSIX.1-2001),
           then only root may change the owner of a file, and nonroot can set
           the group of a file only to one of the groups it belongs to.  This
           affects the following functions:
    
               _chown_()
               _fchown_()
    
       **CS - _POSIX_CLOCK_SELECTION - _SC_CLOCK_SELECTION**
           This option implies the **_POSIX_TIMERS** option.  The following
           functions are present:
    
               _pthread_condattr_getclock_()
               _pthread_condattr_setclock_()
               _clock_nanosleep_()
    
           If **CLOCK_REALTIME** is changed by the function _clock_settime_(), then
           this affects all timers set for an absolute time.
    
       **CPT - _POSIX_CPUTIME - _SC_CPUTIME**
           The **CLOCK_PROCESS_CPUTIME_ID** clock ID is supported.  The initial
           value of this clock is 0 for each process.  This option implies
           the **_POSIX_TIMERS** option.  The function _clock_getcpuclockid_() is
           present.
    
       **--- - _POSIX_FILE_LOCKING - _SC_FILE_LOCKING**
           This option has been deleted.  Not in final XPG6.
    
       **FSC - _POSIX_FSYNC - _SC_FSYNC**
           The function _fsync_() is present.
    
       **IP6 - _POSIX_IPV6 - _SC_IPV6**
           Internet Protocol Version 6 is supported.
    
       **--- - _POSIX_JOB_CONTROL - _SC_JOB_CONTROL**
           If this option is in effect (as it always is under POSIX.1-2001),
           then the system implements POSIX-style job control, and the
           following functions are present:
    
               _setpgid_()
               _tcdrain_()
               _tcflush_()
               _tcgetpgrp_()
               _tcsendbreak_()
               _tcsetattr_()
               _tcsetpgrp_()
    
       **MF - _POSIX_MAPPED_FILES - _SC_MAPPED_FILES**
           Shared memory is supported.  The include file _< sys/mman.h>_ is
           present.  The following functions are present:
    
               _mmap_()
               _msync_()
               _munmap_()
    
       **ML - _POSIX_MEMLOCK - _SC_MEMLOCK**
           Shared memory can be locked into core.  The following functions
           are present:
    
               _mlockall_()
               _munlockall_()
    
       **MR/MLR - _POSIX_MEMLOCK_RANGE - _SC_MEMLOCK_RANGE**
           More precisely, ranges can be locked into core.  The following
           functions are present:
    
               _mlock_()
               _munlock_()
    
       **MPR - _POSIX_MEMORY_PROTECTION - _SC_MEMORY_PROTECTION**
           The function _mprotect_() is present.
    
       **MSG - _POSIX_MESSAGE_PASSING - _SC_MESSAGE_PASSING**
           The include file _< mqueue.h>_ is present.  The following functions
           are present:
    
               _mq_close_()
               _mq_getattr_()
               _mq_notify_()
               _mq_open_()
               _mq_receive_()
               _mq_send_()
               _mq_setattr_()
               _mq_unlink_()
    
       **MON - _POSIX_MONOTONIC_CLOCK - _SC_MONOTONIC_CLOCK**
           **CLOCK_MONOTONIC** is supported.  This option implies the
           **_POSIX_TIMERS** option.  The following functions are affected:
    
               _aio_suspend_()
               _clock_getres_()
               _clock_gettime_()
               _clock_settime_()
               _timer_create_()
    
       **--- - _POSIX_MULTI_PROCESS - _SC_MULTI_PROCESS**
           This option has been deleted.  Not in final XPG6.
    
       **--- - _POSIX_NO_TRUNC**
           If this option is in effect (as it always is under POSIX.1-2001),
           then pathname components longer than **NAME_MAX** are not truncated,
           but give an error.  This property may be dependent on the path
           prefix of the component.
    
       **PIO - _POSIX_PRIORITIZED_IO - _SC_PRIORITIZED_IO**
           This option says that one can specify priorities for asynchronous
           I/O.  This affects the functions
    
               _aio_read_()
               _aio_write_()
    
       **PS - _POSIX_PRIORITY_SCHEDULING - _SC_PRIORITY_SCHEDULING**
           The include file _< sched.h>_ is present.  The following functions
           are present:
    
               _sched_get_priority_max_()
               _sched_get_priority_min_()
               _sched_getparam_()
               _sched_getscheduler_()
               _sched_rr_get_interval_()
               _sched_setparam_()
               _sched_setscheduler_()
               _sched_yield_()
    
           If also **_POSIX_SPAWN** is in effect, then the following functions
           are present:
    
               _posix_spawnattr_getschedparam_()
               _posix_spawnattr_getschedpolicy_()
               _posix_spawnattr_setschedparam_()
               _posix_spawnattr_setschedpolicy_()
    
       **RS - _POSIX_RAW_SOCKETS**
           Raw sockets are supported.  The following functions are affected:
    
               _getsockopt_()
               _setsockopt_()
    
       **--- - _POSIX_READER_WRITER_LOCKS - _SC_READER_WRITER_LOCKS**
           This option implies the **_POSIX_THREADS** option.  Conversely, under
           POSIX.1-2001 the **_POSIX_THREADS** option implies this option.
    
           The following functions are present:
    
               _pthread_rwlock_destroy_()
               _pthread_rwlock_init_()
               _pthread_rwlock_rdlock_()
               _pthread_rwlock_tryrdlock_()
               _pthread_rwlock_trywrlock_()
               _pthread_rwlock_unlock_()
               _pthread_rwlock_wrlock_()
               _pthread_rwlockattr_destroy_()
               _pthread_rwlockattr_init_()
    
       **RTS - _POSIX_REALTIME_SIGNALS - _SC_REALTIME_SIGNALS**
           Realtime signals are supported.  The following functions are
           present:
    
               _sigqueue_()
               _sigtimedwait_()
               _sigwaitinfo_()
    
       **--- - _POSIX_REGEXP - _SC_REGEXP**
           If this option is in effect (as it always is under POSIX.1-2001),
           then POSIX regular expressions are supported and the following
           functions are present:
    
               _regcomp_()
               _regerror_()
               _regexec_()
               _regfree_()
    
       **--- - _POSIX_SAVED_IDS - _SC_SAVED_IDS**
           If this option is in effect (as it always is under POSIX.1-2001),
           then a process has a saved set-user-ID and a saved set-group-ID.
           The following functions are affected:
    
               _exec_()
               _kill_()
               _seteuid_()
               _setegid_()
               _setgid_()
               _setuid_()
    
       **SEM - _POSIX_SEMAPHORES - _SC_SEMAPHORES**
           The include file _< semaphore.h>_ is present.  The following
           functions are present:
    
               _sem_close_()
               _sem_destroy_()
               _sem_getvalue_()
               _sem_init_()
               _sem_open_()
               _sem_post_()
               _sem_trywait_()
               _sem_unlink_()
               _sem_wait_()
    
       **SHM - _POSIX_SHARED_MEMORY_OBJECTS - _SC_SHARED_MEMORY_OBJECTS**
           The following functions are present:
    
               _mmap_()
               _munmap_()
               _shm_open_()
               _shm_unlink_()
    
       **--- - _POSIX_SHELL - _SC_SHELL**
           If this option is in effect (as it always is under POSIX.1-2001),
           the function _system_() is present.
    
       **SPN - _POSIX_SPAWN - _SC_SPAWN**
           This option describes support for process creation in a context
           where it is difficult or impossible to use _fork_(), for example,
           because no MMU is present.
    
           If **_POSIX_SPAWN** is in effect, then the include file _< spawn.h>_ and
           the following functions are present:
    
               _posix_spawn_()
               _posix_spawn_file_actions_addclose_()
               _posix_spawn_file_actions_adddup2_()
               _posix_spawn_file_actions_addopen_()
               _posix_spawn_file_actions_destroy_()
               _posix_spawn_file_actions_init_()
               _posix_spawnattr_destroy_()
               _posix_spawnattr_getsigdefault_()
               _posix_spawnattr_getflags_()
               _posix_spawnattr_getpgroup_()
               _posix_spawnattr_getsigmask_()
               _posix_spawnattr_init_()
               _posix_spawnattr_setsigdefault_()
               _posix_spawnattr_setflags_()
               _posix_spawnattr_setpgroup_()
               _posix_spawnattr_setsigmask_()
               _posix_spawnp_()
    
           If also **_POSIX_PRIORITY_SCHEDULING** is in effect, then the
           following functions are present:
    
               _posix_spawnattr_getschedparam_()
               _posix_spawnattr_getschedpolicy_()
               _posix_spawnattr_setschedparam_()
               _posix_spawnattr_setschedpolicy_()
    
       **SPI - _POSIX_SPIN_LOCKS - _SC_SPIN_LOCKS**
           This option implies the **_POSIX_THREADS** and
           **_POSIX_THREAD_SAFE_FUNCTIONS** options.  The following functions are
           present:
    
               _pthread_spin_destroy_()
               _pthread_spin_init_()
               _pthread_spin_lock_()
               _pthread_spin_trylock_()
               _pthread_spin_unlock_()
    
       **SS - _POSIX_SPORADIC_SERVER - _SC_SPORADIC_SERVER**
           The scheduling policy **SCHED_SPORADIC** is supported.  This option
           implies the **_POSIX_PRIORITY_SCHEDULING** option.  The following
           functions are affected:
    
               _sched_setparam_()
               _sched_setscheduler_()
    
       **SIO - _POSIX_SYNCHRONIZED_IO - _SC_SYNCHRONIZED_IO**
           The following functions are affected:
    
               _open_()
               _msync_()
               _fsync_()
               _fdatasync_()
    
       **TSA - _POSIX_THREAD_ATTR_STACKADDR - _SC_THREAD_ATTR_STACKADDR**
           The following functions are affected:
    
               _pthread_attr_getstack_()
               _pthread_attr_getstackaddr_()
               _pthread_attr_setstack_()
               _pthread_attr_setstackaddr_()
    
       **TSS - _POSIX_THREAD_ATTR_STACKSIZE - _SC_THREAD_ATTR_STACKSIZE**
           The following functions are affected:
    
               _pthread_attr_getstack_()
               _pthread_attr_getstacksize_()
               _pthread_attr_setstack_()
               _pthread_attr_setstacksize_()
    
       **TCT - _POSIX_THREAD_CPUTIME - _SC_THREAD_CPUTIME**
           The clockID CLOCK_THREAD_CPUTIME_ID is supported.  This option
           implies the **_POSIX_TIMERS** option.  The following functions are
           affected:
    
               _pthread_getcpuclockid_()
               _clock_getres_()
               _clock_gettime_()
               _clock_settime_()
               _timer_create_()
    
       **TPI - _POSIX_THREAD_PRIO_INHERIT - _SC_THREAD_PRIO_INHERIT**
           The following functions are affected:
    
               _pthread_mutexattr_getprotocol_()
               _pthread_mutexattr_setprotocol_()
    
       **TPP - _POSIX_THREAD_PRIO_PROTECT - _SC_THREAD_PRIO_PROTECT**
           The following functions are affected:
    
               _pthread_mutex_getprioceiling_()
               _pthread_mutex_setprioceiling_()
               _pthread_mutexattr_getprioceiling_()
               _pthread_mutexattr_getprotocol_()
               _pthread_mutexattr_setprioceiling_()
               _pthread_mutexattr_setprotocol_()
    
       **TPS - _POSIX_THREAD_PRIORITY_SCHEDULING -**
           **_SC_THREAD_PRIORITY_SCHEDULING**
           If this option is in effect, the different threads inside a
           process can run with different priorities and/or different
           schedulers.  The following functions are affected:
    
               _pthread_attr_getinheritsched_()
               _pthread_attr_getschedpolicy_()
               _pthread_attr_getscope_()
               _pthread_attr_setinheritsched_()
               _pthread_attr_setschedpolicy_()
               _pthread_attr_setscope_()
               _pthread_getschedparam_()
               _pthread_setschedparam_()
               _pthread_setschedprio_()
    
       **TSH - _POSIX_THREAD_PROCESS_SHARED - _SC_THREAD_PROCESS_SHARED**
           The following functions are affected:
    
               _pthread_barrierattr_getpshared_()
               _pthread_barrierattr_setpshared_()
               _pthread_condattr_getpshared_()
               _pthread_condattr_setpshared_()
               _pthread_mutexattr_getpshared_()
               _pthread_mutexattr_setpshared_()
               _pthread_rwlockattr_getpshared_()
               _pthread_rwlockattr_setpshared_()
    
       **TSF - _POSIX_THREAD_SAFE_FUNCTIONS - _SC_THREAD_SAFE_FUNCTIONS**
           The following functions are affected:
    
               _readdir_r_()
               _getgrgid_r_()
               _getgrnam_r_()
               _getpwnam_r_()
               _getpwuid_r_()
               _flockfile_()
               _ftrylockfile_()
               _funlockfile_()
               _getc_unlocked_()
               _getchar_unlocked_()
               _putc_unlocked_()
               _putchar_unlocked_()
               _rand_r_()
               _strerror_r_()
               _strtok_r_()
               _asctime_r_()
               _ctime_r_()
               _gmtime_r_()
               _localtime_r_()
    
       **TSP - _POSIX_THREAD_SPORADIC_SERVER - _SC_THREAD_SPORADIC_SERVER**
           This option implies the **_POSIX_THREAD_PRIORITY_SCHEDULING** option.
           The following functions are affected:
    
               _sched_getparam_()
               _sched_setparam_()
               _sched_setscheduler_()
    
       **THR - _POSIX_THREADS - _SC_THREADS**
           Basic support for POSIX threads is available.  The following
           functions are present:
    
               _pthread_atfork_()
               _pthread_attr_destroy_()
               _pthread_attr_getdetachstate_()
               _pthread_attr_getschedparam_()
               _pthread_attr_init_()
               _pthread_attr_setdetachstate_()
               _pthread_attr_setschedparam_()
               _pthread_cancel_()
               _pthread_cleanup_push_()
               _pthread_cleanup_pop_()
               _pthread_cond_broadcast_()
               _pthread_cond_destroy_()
               _pthread_cond_init_()
               _pthread_cond_signal_()
               _pthread_cond_timedwait_()
               _pthread_cond_wait_()
               _pthread_condattr_destroy_()
               _pthread_condattr_init_()
               _pthread_create_()
               _pthread_detach_()
               _pthread_equal_()
               _pthread_exit_()
               _pthread_getspecific_()
               _pthread_join_()
               _pthread_key_create_()
               _pthread_key_delete_()
               _pthread_mutex_destroy_()
               _pthread_mutex_init_()
               _pthread_mutex_lock_()
               _pthread_mutex_trylock_()
               _pthread_mutex_unlock_()
               _pthread_mutexattr_destroy_()
               _pthread_mutexattr_init_()
               _pthread_once_()
               _pthread_rwlock_destroy_()
               _pthread_rwlock_init_()
               _pthread_rwlock_rdlock_()
               _pthread_rwlock_tryrdlock_()
               _pthread_rwlock_trywrlock_()
               _pthread_rwlock_unlock_()
               _pthread_rwlock_wrlock_()
               _pthread_rwlockattr_destroy_()
               _pthread_rwlockattr_init_()
               _pthread_self_()
               _pthread_setcancelstate_()
               _pthread_setcanceltype_()
               _pthread_setspecific_()
               _pthread_testcancel_()
    
       **TMO - _POSIX_TIMEOUTS - _SC_TIMEOUTS**
           The following functions are present:
    
               _mq_timedreceive_()
               _mq_timedsend_()
               _pthread_mutex_timedlock_()
               _pthread_rwlock_timedrdlock_()
               _pthread_rwlock_timedwrlock_()
               _sem_timedwait_()
               _posix_trace_timedgetnext_event_()
    
       **TMR - _POSIX_TIMERS - _SC_TIMERS**
           The following functions are present:
    
               _clock_getres_()
               _clock_gettime_()
               _clock_settime_()
               _nanosleep_()
               _timer_create_()
               _timer_delete_()
               _timer_gettime_()
               _timer_getoverrun_()
               _timer_settime_()
    
       **TRC - _POSIX_TRACE - _SC_TRACE**
           POSIX tracing is available.  The following functions are present:
    
               _posix_trace_attr_destroy_()
               _posix_trace_attr_getclockres_()
               _posix_trace_attr_getcreatetime_()
               _posix_trace_attr_getgenversion_()
               _posix_trace_attr_getmaxdatasize_()
               _posix_trace_attr_getmaxsystemeventsize_()
               _posix_trace_attr_getmaxusereventsize_()
               _posix_trace_attr_getname_()
               _posix_trace_attr_getstreamfullpolicy_()
               _posix_trace_attr_getstreamsize_()
               _posix_trace_attr_init_()
               _posix_trace_attr_setmaxdatasize_()
               _posix_trace_attr_setname_()
               _posix_trace_attr_setstreamsize_()
               _posix_trace_attr_setstreamfullpolicy_()
               _posix_trace_clear_()
               _posix_trace_create_()
               _posix_trace_event_()
               _posix_trace_eventid_equal_()
               _posix_trace_eventid_get_name_()
               _posix_trace_eventid_open_()
               _posix_trace_eventtypelist_getnext_id_()
               _posix_trace_eventtypelist_rewind_()
               _posix_trace_flush_()
               _posix_trace_get_attr_()
               _posix_trace_get_status_()
               _posix_trace_getnext_event_()
               _posix_trace_shutdown_()
               _posix_trace_start_()
               _posix_trace_stop_()
               _posix_trace_trygetnext_event_()
    
       **TEF - _POSIX_TRACE_EVENT_FILTER - _SC_TRACE_EVENT_FILTER**
           This option implies the **_POSIX_TRACE** option.  The following
           functions are present:
    
               _posix_trace_eventset_add_()
               _posix_trace_eventset_del_()
               _posix_trace_eventset_empty_()
               _posix_trace_eventset_fill_()
               _posix_trace_eventset_ismember_()
               _posix_trace_get_filter_()
               _posix_trace_set_filter_()
               _posix_trace_trid_eventid_open_()
    
       **TRI - _POSIX_TRACE_INHERIT - _SC_TRACE_INHERIT**
           Tracing children of the traced process is supported.  This option
           implies the **_POSIX_TRACE** option.  The following functions are
           present:
    
               _posix_trace_attr_getinherited_()
               _posix_trace_attr_setinherited_()
    
       **TRL - _POSIX_TRACE_LOG - _SC_TRACE_LOG**
           This option implies the **_POSIX_TRACE** option.  The following
           functions are present:
    
               _posix_trace_attr_getlogfullpolicy_()
               _posix_trace_attr_getlogsize_()
               _posix_trace_attr_setlogfullpolicy_()
               _posix_trace_attr_setlogsize_()
               _posix_trace_close_()
               _posix_trace_create_withlog_()
               _posix_trace_open_()
               _posix_trace_rewind_()
    
       **TYM - _POSIX_TYPED_MEMORY_OBJECTS - _SC_TYPED_MEMORY_OBJECT**
           The following functions are present:
    
               _posix_mem_offset_()
               _posix_typed_mem_get_info_()
               _posix_typed_mem_open_()
    
       **--- - _POSIX_VDISABLE**
           Always present (probably 0).  Value to set a changeable special
           control character to indicate that it is disabled.
    


## X/OPEN SYSTEM INTERFACE EXTENSIONS



       **XSI - _XOPEN_CRYPT - _SC_XOPEN_CRYPT**
           The following functions are present:
    
               _crypt_()
               _encrypt_()
               _setkey_()
    
       **XSI - _XOPEN_REALTIME - _SC_XOPEN_REALTIME**
           This option implies the following options:
    
           **_POSIX_ASYNCHRONOUS_IO** ==**200112L**
           **_POSIX_FSYNC**
           **_POSIX_MAPPED_FILES**
           **_POSIX_MEMLOCK** ==**200112L**
           **_POSIX_MEMLOCK_RANGE** ==**200112L**
           **_POSIX_MEMORY_PROTECTION**
           **_POSIX_MESSAGE_PASSING** ==**200112L**
           **_POSIX_PRIORITIZED_IO**
           **_POSIX_PRIORITY_SCHEDULING** ==**200112L**
           **_POSIX_REALTIME_SIGNALS** ==**200112L**
           **_POSIX_SEMAPHORES** ==**200112L**
           **_POSIX_SHARED_MEMORY_OBJECTS** ==**200112L**
           **_POSIX_SYNCHRONIZED_IO** ==**200112L**
           **_POSIX_TIMERS** ==**200112L**
    
       **ADV - --- - ---**
           The Advanced Realtime option group implies that the following
           options are all defined to 200112L:
    
           **_POSIX_ADVISORY_INFO**
           **_POSIX_CLOCK_SELECTION**
                  (implies **_POSIX_TIMERS**)
           **_POSIX_CPUTIME**
                  (implies **_POSIX_TIMERS**)
           **_POSIX_MONOTONIC_CLOCK**
                  (implies **_POSIX_TIMERS**)
           **_POSIX_SPAWN**
           **_POSIX_SPORADIC_SERVER**
                  (implies **_POSIX_PRIORITY_SCHEDULING**)
           **_POSIX_TIMEOUTS**
           **_POSIX_TYPED_MEMORY_OBJECTS**
    
       **XSI - _XOPEN_REALTIME_THREADS - _SC_XOPEN_REALTIME_THREADS**
           This option implies that the following options are all defined to
           200112L:
    
           **_POSIX_THREAD_PRIO_INHERIT**
           **_POSIX_THREAD_PRIO_PROTECT**
           **_POSIX_THREAD_PRIORITY_SCHEDULING**
    
       **ADVANCED REALTIME THREADS - --- - ---**
           This option implies that the following options are all defined to
           200112L:
    
           **_POSIX_BARRIERS**
                  (implies **_POSIX_THREADS** , **_POSIX_THREAD_SAFE_FUNCTIONS**)
           **_POSIX_SPIN_LOCKS**
                  (implies **_POSIX_THREADS** , **_POSIX_THREAD_SAFE_FUNCTIONS**)
           **_POSIX_THREAD_CPUTIME**
                  (implies **_POSIX_TIMERS**)
           **_POSIX_THREAD_SPORADIC_SERVER**
                  (implies **_POSIX_THREAD_PRIORITY_SCHEDULING**)
    
       **TRACING - --- - ---**
           This option implies that the following options are all defined to
           200112L:
    
           **_POSIX_TRACE**
           **_POSIX_TRACE_EVENT_FILTER**
           **_POSIX_TRACE_LOG**
           **_POSIX_TRACE_INHERIT**
    
       **STREAMS - _XOPEN_STREAMS - _SC_XOPEN_STREAMS**
           The following functions are present:
    
               _fattach_()
               _fdetach_()
               _getmsg_()
               _getpmsg_()
               _ioctl_()
               _isastream_()
               _putmsg_()
               _putpmsg_()
    
       **XSI - _XOPEN_LEGACY - _SC_XOPEN_LEGACY**
           Functions included in the legacy option group were previously
           mandatory, but are now optional in this version.  The following
           functions are present:
    
               _bcmp_()
               _bcopy_()
               _bzero_()
               _ecvt_()
               _fcvt_()
               _ftime_()
               _gcvt_()
               _getwd_()
               _index_()
               _mktemp_()
               _rindex_()
               _utimes_()
               _wcswcs_()
    
       **XSI - _XOPEN_UNIX - _SC_XOPEN_UNIX**
           The following functions are present:
    
               _mmap_()
               _munmap_()
               _msync_()
    
           This option implies the following options:
    
           **_POSIX_FSYNC**
           **_POSIX_MAPPED_FILES**
           **_POSIX_MEMORY_PROTECTION**
           **_POSIX_THREAD_ATTR_STACKADDR**
           **_POSIX_THREAD_ATTR_STACKSIZE**
           **_POSIX_THREAD_PROCESS_SHARED**
           **_POSIX_THREAD_SAFE_FUNCTIONS**
           **_POSIX_THREADS**
    
           This option may imply the following options from the XSI option
           groups:
    
           Encryption (**_XOPEN_CRYPT**)
           Realtime (**_XOPEN_REALTIME**)
           Advanced Realtime (**ADB**)
           Realtime Threads (**_XOPEN_REALTIME_THREADS**)
           Advanced Realtime Threads (**ADVANCED REALTIME THREADS**)
           Tracing (**TRACING**)
           XSI Streams (**STREAMS**)
           Legacy (**_XOPEN_LEGACY**)
    


* * *