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📖 NAME

posixoptions - optional parts of the POSIX standard

🚀 Quick Reference

Use Case	Option Constant	sysconf Parameter
Check advisory info support	_POSIX_ADVISORY_INFO	_SC_ADVISORY_INFO
Check asynchronous I/O support	_POSIX_ASYNCHRONOUS_IO	_SC_ASYNCHRONOUS_IO
Check barrier support	_POSIX_BARRIERS	_SC_BARRIERS
Check clock selection support	_POSIX_CLOCK_SELECTION	_SC_CLOCK_SELECTION
Check CPU time support	_POSIX_CPUTIME	_SC_CPUTIME
Check fsync support	_POSIX_FSYNC	_SC_FSYNC
Check IPv6 support	_POSIX_IPV6	_SC_IPV6
Check job control support	_POSIX_JOB_CONTROL	_SC_JOB_CONTROL
Check mapped files support	_POSIX_MAPPED_FILES	_SC_MAPPED_FILES
Check memory locking support	_POSIX_MEMLOCK	_SC_MEMLOCK
Check memory locking range support	_POSIX_MEMLOCK_RANGE	_SC_MEMLOCK_RANGE
Check memory protection support	_POSIX_MEMORY_PROTECTION	_SC_MEMORY_PROTECTION
Check message passing support	_POSIX_MESSAGE_PASSING	_SC_MESSAGE_PASSING
Check monotonic clock support	_POSIX_MONOTONIC_CLOCK	_SC_MONOTONIC_CLOCK
Check prioritized I/O support	_POSIX_PRIORITIZED_IO	_SC_PRIORITIZED_IO
Check priority scheduling support	_POSIX_PRIORITY_SCHEDULING	_SC_PRIORITY_SCHEDULING
Check raw sockets support	_POSIX_RAW_SOCKETS	—
Check realtime signals support	_POSIX_REALTIME_SIGNALS	_SC_REALTIME_SIGNALS
Check semaphores support	_POSIX_SEMAPHORES	_SC_SEMAPHORES
Check shared memory objects support	_POSIX_SHARED_MEMORY_OBJECTS	_SC_SHARED_MEMORY_OBJECTS
Check spawn support	_POSIX_SPAWN	_SC_SPAWN
Check spin locks support	_POSIX_SPIN_LOCKS	_SC_SPIN_LOCKS
Check sporadic server support	_POSIX_SPORADIC_SERVER	_SC_SPORADIC_SERVER
Check synchronized I/O support	_POSIX_SYNCHRONIZED_IO	_SC_SYNCHRONIZED_IO
Check thread stack address support	_POSIX_THREAD_ATTR_STACKADDR	_SC_THREAD_ATTR_STACKADDR
Check thread stack size support	_POSIX_THREAD_ATTR_STACKSIZE	_SC_THREAD_ATTR_STACKSIZE
Check thread CPU time support	_POSIX_THREAD_CPUTIME	_SC_THREAD_CPUTIME
Check thread priority inheritance support	_POSIX_THREAD_PRIO_INHERIT	_SC_THREAD_PRIO_INHERIT
Check thread priority protection support	_POSIX_THREAD_PRIO_PROTECT	_SC_THREAD_PRIO_PROTECT
Check thread priority scheduling support	_POSIX_THREAD_PRIORITY_SCHEDULING	_SC_THREAD_PRIORITY_SCHEDULING
Check thread process shared support	_POSIX_THREAD_PROCESS_SHARED	_SC_THREAD_PROCESS_SHARED
Check thread safe functions support	_POSIX_THREAD_SAFE_FUNCTIONS	_SC_THREAD_SAFE_FUNCTIONS
Check thread sporadic server support	_POSIX_THREAD_SPORADIC_SERVER	_SC_THREAD_SPORADIC_SERVER
Check basic thread support	_POSIX_THREADS	_SC_THREADS
Check timeouts support	_POSIX_TIMEOUTS	_SC_TIMEOUTS
Check timers support	_POSIX_TIMERS	_SC_TIMERS
Check trace support	_POSIX_TRACE	_SC_TRACE
Check trace event filter support	_POSIX_TRACE_EVENT_FILTER	_SC_TRACE_EVENT_FILTER
Check trace inherit support	_POSIX_TRACE_INHERIT	_SC_TRACE_INHERIT
Check trace log support	_POSIX_TRACE_LOG	_SC_TRACE_LOG
Check typed memory objects support	_POSIX_TYPED_MEMORY_OBJECTS	_SC_TYPED_MEMORY_OBJECT

📝 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

ℹ️ 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 (no abbreviation)

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ Shared memory can be locked into core. The following functions are present:

• mlockall()
• munlockall()

🔹 MR/MLR - _POSIX_MEMLOCK_RANGE - _SC_MEMLOCK_RANGE

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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()

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ If this option is in effect (as it always is under POSIX.1-2001), the function system() is present.

🔹 SPN - _POSIX_SPAWN - _SC_SPAWN

ℹ️ 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()

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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 - (Advanced Realtime) - no sysconf constant

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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

ℹ️ 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()

ℹ️ 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

ℹ️ 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 5.10 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

📖 NAME 🚀 Quick Reference 📝 DESCRIPTION 🔗 X/OPEN SYSTEM INTERFACE EXTENSIONS 📚 SEE ALSO 📄 COLOPHON