POSIXOPTIONS(7)

NAME
posixoptions - optional parts of the POSIX standard

DESCRIPTION
The POSIX standard (the information below is from POSIX 1003.1-2001) describes a set of behaviours 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() 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 advisory functions
posix_fadvise(),
posix_fallocate(),
posix_memalign(),
posix_madvise()
are present.

  AIO - _POSIX_ASYNCHRONOUS_IO - _SC_ASYNCHRONOUS_IO
The header <aio.h> is present. The functions
aio_cancel(),
aio_error(),
aio_fsync(),
aio_read(),
aio_return(),
aio_suspend(),
aio_write(),
lio_listio()
are present.

  BAR - _POSIX_BARRIERS - _SC_BARRIERS
This option implies the _POSIX_THREADS and _POSIX_THREAD_SAFE_FUNCTIONS options. The functions
pthread_barrier_destroy(),
pthread_barrier_init(),
pthread_barrier_wait(),
pthread_barrierattr_destroy(),
pthread_barrierattr_init()
are present.

  --- - POSIX_CHOWN_RESTRICTED
If this option is in effect (as it always is under POSIX 1003.1-2001) then only root may change the owner of a file, and non-root can only set the group of a file to one of the groups it belongs to. This affects the functions chown(), fchown().

  CS - _POSIX_CLOCK_SELECTION - _SC_CLOCK_SELECTION
This option implies the _POSIX_TIMERS option. The functions
pthread_condattr_getclock(),
pthread_condattr_setclock(),
clock_nanosleep()
are present. 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 clockID CLOCK_PROCESS_CPUTIME_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 1003.1-2001) then the system implements POSIX - style job control, and the functions
setpgid(),
tcdrain(),
tcflush(),
tcgetpgrp(),
tcsendbreak(),
tcsetattr(),
tcsetpgrp()
are present.

  MF - _POSIX_MAPPED_FILES - _SC_MAPPED_FILES
Shared memory is supported. The include file <sys/mman.h> is present. The functions mmap(), msync(), munmap() are present.

  ML - _POSIX_MEMLOCK - _SC_MEMLOCK
Shared memory can be locked into core. The functions mlockall(), munlockall() are present.

  MR/MLR - _POSIX_MEMLOCK_RANGE - _SC_MEMLOCK_RANGE
More precisely, ranges can be locked into core. The functions mlock(), munlock() are present.

  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 functions
mq_close(),
mq_getattr(),
mq_notify(),
mq_open(),
mq_receive(),
mq_send(),
mq_setattr(),
mq_unlink()
are present.

  MON - _POSIX_MONOTONIC_CLOCK - _SC_MONOTONIC_CLOCK
CLOCK_MONOTONIC is supported.
This option implies the _POSIX_TIMERS option.
Affected functions are
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 1003.1-2001) 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 functions
sched_get_priority_max(),
sched_get_priority_min(),
sched_getparam(),
sched_getscheduler(),
sched_rr_get_interval(),
sched_setparam(),
sched_setscheduler(),
sched_yield()
are present. If also _POSIX_SPAWN is in effect, then the functions
posix_spawnattr_getschedparam(),
posix_spawnattr_getschedpolicy(),
posix_spawnattr_setschedparam(),
posix_spawnattr_setschedpolicy()
are present.

  RS - _POSIX_RAW_SOCKETS
Raw sockets are supported. Affected functions are getsockopt(), setsockopt().

  --- - _POSIX_READER_WRITER_LOCKS - _SC_READER_WRITER_LOCKS
This option implies the _POSIX_THREADS option. Conversely, under POSIX 1003.1-2001 the _POSIX_THREADS option implies this option.
The functions
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()
are present.

  RTS - _POSIX_REALTIME_SIGNALS - _SC_REALTIME_SIGNALS
Realtime signals are supported. The functions
sigqueue(),
sigtimedwait(),
sigwaitinfo()
are present.

  --- - _POSIX_REGEXP - _SC_REGEXP
If this option is in effect (as it always is under POSIX 1003.1-2001) then POSIX regular expressions are supported and the functions
regcomp(),
regerror(),
regexec(),
regfree()
are present.

  --- - _POSIX_SAVED_IDS - _SC_SAVED_IDS
If this option is in effect (as it always is under POSIX 1003.1-2001) then a process has a saved set-user-ID and a saved set-group-ID. Affected functions are
exec(),
kill(),
seteuid(),
setegid(),
setgid(),
setuid().

  SEM - _POSIX_SEMAPHORES - _SC_SEMAPHORES
The include file <semaphore.h> is present. The functions
sem_close(),
sem_destroy(),
sem_getvalue(),
sem_init(),
sem_open(),
sem_post(),
sem_trywait(),
sem_unlink(),
sem_wait()
are present.

  SHM - _POSIX_SHARED_MEMORY_OBJECTS - _SC_SHARED_MEMORY_OBJECTS
The functions
mmap(),
munmap(),
shm_open(),
shm_unlink()
are present.

  --- - _POSIX_SHELL - _SC_SHELL
If this option is in effect (as it always is under POSIX 1003.1-2001), 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(), e.g. because no MMU is present. If _POSIX_SPAWN is in effect, then the include file <spawn.h> and the functions
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()
are present. If also _POSIX_PRIORITY_SCHEDULING is in effect, then the functions
posix_spawnattr_getschedparam(),
posix_spawnattr_getschedpolicy(),
posix_spawnattr_setschedparam(),
posix_spawnattr_setschedpolicy()
are present.

  SPI - _POSIX_SPIN_LOCKS - _SC_SPIN_LOCKS
This option implies the _POSIX_THREADS and _POSIX_THREAD_SAFE_FUNCTIONS options. The functions
pthread_spin_destroy(),
pthread_spin_init(),
pthread_spin_lock(),
pthread_spin_trylock(),
pthread_spin_unlock()
are present.

  SS - _POSIX_SPORADIC_SERVER - _SC_SPORADIC_SERVER
The scheduling policy SCHED_SPORADIC is supported. This option implies the _POSIX_PRIORITY_SCHEDULING option. Affected functions are
sched_setparam(),
sched_setscheduler().

  SIO - _POSIX_SYNCHRONIZED_IO - _SC_SYNCHRONIZED_IO
Affected functions are open(), msync(), fsync(), fdatasync().

  TSA - _POSIX_THREAD_ATTR_STACKADDR - _SC_THREAD_ATTR_STACKADDR
Affected functions are
pthread_attr_getstack(),
pthread_attr_getstackaddr(),
pthread_attr_setstack(),
pthread_attr_setstackaddr().

  TSS - _POSIX_THREAD_ATTR_STACKSIZE - _SC_THREAD_ATTR_STACKSIZE
Affected functions are
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. Affected functions are
pthread_getcpuclockid(),
clock_getres(),
clock_gettime(),
clock_settime(),
timer_create().

  TPI - _POSIX_THREAD_PRIO_INHERIT - _SC_THREAD_PRIO_INHERIT
Affected functions are
pthread_mutexattr_getprotocol(),
pthread_mutexattr_setprotocol().

  TPP - _POSIX_THREAD_PRIO_PROTECT - _SC_THREAD_PRIO_PROTECT
Affected functions are
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. Affected functions are
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
Affected functions are
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
Affected functions are
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. Affected functions are
sched_getparam(),
sched_setparam(),
sched_setscheduler().

  THR - _POSIX_THREADS - _SC_THREADS
Basic support for POSIX threads is available. The functions
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()
are present.

  TMO - _POSIX_TIMEOUTS - _SC_TIMEOUTS
The functions
mq_timedreceive(),
mq_timedsend(),
pthread_mutex_timedlock(),
pthread_rwlock_timedrdlock(),
pthread_rwlock_timedwrlock(),
sem_timedwait(),
posix_trace_timedgetnext_event()
are present.

  TMR - _POSIX_TIMERS - _SC_TIMERS
The functions
clock_getres(),
clock_gettime(),
clock_settime(),
nanosleep(),
timer_create(),
timer_delete(),
timer_gettime(),
timer_getoverrun(),
timer_settime()
are present.

  TRC - _POSIX_TRACE - _SC_TRACE
POSIX tracing is available. The functions
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()
are present.

  TEF - _POSIX_TRACE_EVENT_FILTER - _SC_TRACE_EVENT_FILTER
This option implies the _POSIX_TRACE option. The functions
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()
are present.

  TRI - _POSIX_TRACE_INHERIT - _SC_TRACE_INHERIT
Tracing children of the traced process is supported. This option implies the _POSIX_TRACE option. The functions
posix_trace_attr_getinherited(),
posix_trace_attr_setinherited()
are present.

  TRL - _POSIX_TRACE_LOG - _SC_TRACE_LOG
This option implies the _POSIX_TRACE option. The functions
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()
are present.

  TYM - _POSIX_TYPED_MEMORY_OBJECTS - _SC_TYPED_MEMORY_OBJECT
The functions
posix_mem_offset(),
posix_typed_mem_get_info(),
posix_typed_mem_open()
are present.

  --- - _POSIX_VDISABLE
Always present (probably 0). Value to set a changeable special control character to to indicate that it is disabled.

XOPEN EXTENSIONS
_XOPEN_CRYPT, _XOPEN_LEGACY, _XOPEN_REALTIME, _XOPEN_REALTIME_THREADS, _XOPEN_UNIX.

SEE ALSO
sysconf(3)