NAME | DESCRIPTION | X/OPEN SYSTEM INTERFACE EXTENSIONS | SEE ALSO | COLOPHON

POSIXOPTIONS(7)           Linux Programmer's Manual          POSIXOPTIONS(7)

NAME         top

       posixoptions - optional parts of the POSIX standard

DESCRIPTION         top

       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         top

   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         top

       sysconf(3), standards(7)

COLOPHON         top

       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)

Pages that refer to this page: sysconf(3)standards(7)