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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 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 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.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 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 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. 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.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. Affected functions are 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. Affected functions are 

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. 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 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.

Xopen Extensions

_XOPEN_CRYPT, _XOPEN_LEGACY, _XOPEN_REALTIME, _XOPEN_REALTIME_THREADS, _XOPEN_UNIX.

See Also

sysconf(3) , standards(7)

Colophon

This page is part of release 3.78 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 http://www.kernel.org/doc/man-pages/.

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