# phpman > info > posixoptions [POSIXOPTIONS(7)](https://www.chedong.com/phpMan.php/man/POSIXOPTIONS/7/markdown) Linux Programmer's Manual [POSIXOPTIONS(7)](https://www.chedong.com/phpMan.php/man/POSIXOPTIONS/7/markdown) NAME posixoptions - optional parts of the POSIX standard DESCRIPTION The POSIX standard (the information below is from POSIX.1-2001) de- scribes a set of behaviors and interfaces for a compliant system. How- ever, many interfaces are optional and there are feature test macros to test the availability of interfaces at compile time, and functions [sysconf(3)](https://www.chedong.com/phpMan.php/man/sysconf/3/markdown), [fpathconf(3)](https://www.chedong.com/phpMan.php/man/fpathconf/3/markdown), [pathconf(3)](https://www.chedong.com/phpMan.php/man/pathconf/3/markdown), [confstr(3)](https://www.chedong.com/phpMan.php/man/confstr/3/markdown) to do this at run time. From shell scripts one can use [getconf(1)](https://www.chedong.com/phpMan.php/man/getconf/1/markdown). For more detail, see [sysconf(3)](https://www.chedong.com/phpMan.php/man/sysconf/3/markdown). We give the name of the POSIX abbreviation, the option, the name of the [sysconf(3)](https://www.chedong.com/phpMan.php/man/sysconf/3/markdown) 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 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 func- tions are present: setpgid() tcdrain() tcflush() tcgetpgrp() tcsendbreak() tcsetattr() tcsetpgrp() MF - _POSIX_MAPPED_FILES - _SC_MAPPED_FILES Shared memory is supported. The include file 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 func- tions 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 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 compo- nent. 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 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 fol- lowing functions are affected: exec() kill() seteuid() setegid() setgid() setuid() SEM - _POSIX_SEMAPHORES - _SC_SEMAPHORES The include file 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 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 af- fected: 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 follow- ing 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 im- plies 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 manda- tory, 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)](https://www.chedong.com/phpMan.php/man/sysconf/3/markdown), [standards(7)](https://www.chedong.com/phpMan.php/man/standards/7/markdown) 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 . 2018-04-30 [POSIXOPTIONS(7)](https://www.chedong.com/phpMan.php/man/POSIXOPTIONS/7/markdown)