port.html

IEEE 1003.1-2003, Single Unix Specification v3

<p>It should only be required if needed, but it should never be prohibited.</p>
</dd>

<dt>_POSIX_MEMORY_PROTECTION</dt>

<dd>
The system supports memory protection. 

<p>XSI-conformant systems support this option.</p>

<p>The provision of this option typically imposes additional hardware requirements. It should never be prohibited.</p>
</dd>

<dt>_POSIX_PRIORITIZED_IO</dt>

<dd>
The system provides prioritization for input and output operations. 

<p>The use of this option may interfere with the ability of the system to optimize input and output throughput. It should only be
required if needed, but it should never be prohibited.</p>
</dd>

<dt>_POSIX_MESSAGE_PASSING</dt>

<dd>
The system supports the passing of messages between processes. 

<p>This option was created to support historical systems that did not provide the feature. The functionality adds a
high-performance XSI interprocess communication facility for local communication. It should only be required if needed, but it
should never be prohibited.</p>
</dd>

<dt>_POSIX_MONOTONIC_CLOCK</dt>

<dd>
The system supports the Monotonic Clock option. 

<p>This option allows realtime applications to rely on a monotonically increasing clock that does not jump backwards, and whose
value does not change except for the regular ticking of the clock.</p>
</dd>

<dt>_POSIX_PRIORITY_SCHEDULING</dt>

<dd>
The system provides priority-based process scheduling. 

<p>Support of this option provides predictable scheduling behavior, allowing applications to determine the order in which processes
that are ready to run are granted access to a processor. It should only be required if needed, but it should never be
prohibited.</p>
</dd>

<dt>_POSIX_REALTIME_SIGNALS</dt>

<dd>
The system provides prioritized, queued signals with associated data values. 

<p>This option was created to support historical systems that did not provide the features. It should only be required if needed,
but it should never be prohibited.</p>
</dd>

<dt>_POSIX_REGEXP</dt>

<dd>
Support for regular expression facilities is mandatory in IEEE&nbsp;Std&nbsp;1003.1-2001.</dd>

<dt>_POSIX_SAVED_IDS</dt>

<dd>
Support for this feature is mandatory in IEEE&nbsp;Std&nbsp;1003.1-2001. 

<p>Certain classes of applications rely on it for proper operation, and there is no alternative short of giving the application
root privileges on most implementations that did not provide _POSIX_SAVED_IDS.</p>
</dd>

<dt>_POSIX_SEMAPHORES</dt>

<dd>
The system provides counting semaphores. 

<p>This option was created to support historical systems that did not provide the feature. It should only be required if needed,
but it should never be prohibited.</p>
</dd>

<dt>_POSIX_SHARED_MEMORY_OBJECTS</dt>

<dd>
The system supports the mapping of shared memory objects into the process address space. 

<p>Both this option and the Memory Mapped Files option provide shared access to memory objects in the process address space. The
functions defined under this option provide the functionality of existing practice for shared memory objects. This functionality
was deemed appropriate for embedded systems applications and, hence, is provided under this option. It should only be required if
needed, but it should never be prohibited.</p>
</dd>

<dt>_POSIX_SHELL</dt>

<dd>
Support for the <a href="../utilities/sh.html"><i>sh</i></a> utility command line interpreter is mandatory in
IEEE&nbsp;Std&nbsp;1003.1-2001.</dd>

<dt>_POSIX_SPAWN</dt>

<dd>
The system supports the spawn option. 

<p>This option provides applications with an efficient mechanism to spawn execution of a new process.</p>
</dd>

<dt>_POSIX_SPINLOCKS</dt>

<dd>
The system supports spin locks. 

<p>This option was created to support a simple and efficient synchronization mechanism for threads executing in multi-processor
systems.</p>
</dd>

<dt>_POSIX_SPORADIC_SERVER</dt>

<dd>
The system supports the sporadic server scheduling policy. 

<p>This option provides applications with a new scheduling policy for scheduling aperiodic processes or threads in hard realtime
applications.</p>
</dd>

<dt>_POSIX_SYNCHRONIZED_IO</dt>

<dd>
The system supports guaranteed file synchronization. 

<p>This option was created to support historical systems that did not provide the feature. Applications that are expecting
guaranteed completion of their input and output operations should require this option, rather than the File Synchronization option.
It should only be required if needed, but it should never be prohibited.</p>
</dd>

<dt>_POSIX_THREADS</dt>

<dd>
The system supports multiple threads of control within a single process. 

<p>This option was created to support historical systems that did not provide the feature. Applications written assuming a
multi-threaded environment would be expected to require this option. It should only be required if needed, but it should never be
prohibited.</p>

<p>XSI-conformant systems support this option.</p>
</dd>

<dt>_POSIX_THREAD_ATTR_STACKADDR</dt>

<dd>
The system supports specification of the stack address for a created thread. 

<p>Applications may take advantage of support of this option for performance benefits, but dependence on this feature should be
minimized. This option should never be prohibited.</p>

<p>XSI-conformant systems support this option.</p>
</dd>

<dt>_POSIX_THREAD_ATTR_STACKSIZE</dt>

<dd>
The system supports specification of the stack size for a created thread. 

<p>Applications may require this option in order to ensure proper execution, but such usage limits portability and dependence on
this feature should be minimized. It should only be required if needed, but it should never be prohibited.</p>

<p>XSI-conformant systems support this option.</p>
</dd>

<dt>_POSIX_THREAD_PRIORITY_SCHEDULING</dt>

<dd>
The system provides priority-based thread scheduling. 

<p>Support of this option provides predictable scheduling behavior, allowing applications to determine the order in which threads
that are ready to run are granted access to a processor. It should only be required if needed, but it should never be
prohibited.</p>
</dd>

<dt>_POSIX_THREAD_PRIO_INHERIT</dt>

<dd>
The system provides mutual-exclusion operations with priority inheritance. 

<p>Support of this option provides predictable scheduling behavior, allowing applications to determine the order in which threads
that are ready to run are granted access to a processor. It should only be required if needed, but it should never be
prohibited.</p>
</dd>

<dt>_POSIX_THREAD_PRIO_PROTECT</dt>

<dd>
The system supports a priority ceiling emulation protocol for mutual-exclusion operations. 

<p>Support of this option provides predictable scheduling behavior, allowing applications to determine the order in which threads
that are ready to run are granted access to a processor. It should only be required if needed, but it should never be
prohibited.</p>
</dd>

<dt>_POSIX_THREAD_PROCESS_SHARED</dt>

<dd>
The system provides shared access among multiple processes to synchronization objects. 

<p>This option was created to support historical systems that did not provide the feature. It should only be required if needed,
but it should never be prohibited.</p>

<p>XSI-conformant systems support this option.</p>
</dd>

<dt>_POSIX_THREAD_SAFE_FUNCTIONS</dt>

<dd>
The system provides thread-safe versions of all of the POSIX.1 functions. 

<p>This option is required if the Threads option is supported. This is a separate option because thread-safe functions are useful
in implementations providing other mechanisms for concurrency. It should only be required if needed, but it should never be
prohibited.</p>

<p>XSI-conformant systems support this option.</p>
</dd>

<dt>_POSIX_THREAD_SPORADIC_SERVER</dt>

<dd>
The system supports the thread sporadic server scheduling policy. 

<p>Support for this option provides applications with a new scheduling policy for scheduling aperiodic threads in hard realtime
applications.</p>
</dd>

<dt>_POSIX_TIMEOUTS</dt>

<dd>
The system provides timeouts for some blocking services. 

<p>This option was created to provide a timeout capability to system services, thus allowing applications to include better error
detection, and recovery capabilities.</p>
</dd>

<dt>_POSIX_TIMERS</dt>

<dd>
The system provides higher resolution clocks with multiple timers per process. 

<p>This option was created to support historical systems that did not provide the features. This option is appropriate for
applications requiring higher resolution timestamps or needing to control the timing of multiple activities. It should only be
required if needed, but it should never be prohibited.</p>
</dd>

<dt>_POSIX_TRACE</dt>

<dd>
The system supports the Trace option. 

<p>This option wa