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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()
           getcwd()
           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)

SEE ALSO

       sysconf(3), standards(7)

COLOPHON

       This  page  is  part of release 4.16 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at https://www.kernel.org/doc/man-pages/.

                                            2018-04-30                            POSIXOPTIONS(7)