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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>Feature Groups</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><blockquote><center><h3><a name = "tag_000_005"> </a>Feature Groups</h3></center><xref type="2" name="feature"></xref><p>The system may provide one or more of the following Feature Groups:<ul><p><li><a href = "#tag_000_005_001">Encryption</a><p><li><a href = "#tag_000_005_002">Realtime</a><p><li><a href = "#tag_000_005_003">Realtime Threads</a><p><li><a href = "#tag_000_005_004">Legacy.</a><p></ul><p>When an implementation claims that a feature is provided, all ofits constituent parts shall be provided and shall comply with thisspecification.<p>For all Feature Groups, interfaces to all elementsof the Feature Group shall exist.On implementations that do not support individual interfaces, eachunsupported interface shall indicate an error, with <i>errno</i>set to[ENOSYS]unless otherwise specified.<p>If individual interfaces are supported, but the whole Feature Group isnot supported, the interfaces will behave as defined in thisspecification.<h4><a name = "tag_000_005_001">Encryption</a></h4>The Encryption Feature Group includes the following interfaces:<pre><dl compact><dt> <dd><i><a href="crypt.html">crypt()</a></i><i><a href="encrypt.html">encrypt()</a></i><i><a href="setkey.html">setkey()</a></i></dl></pre>These are marked <b>CRYPT</b>.<p>Due to U.S. Government export restrictions on the decoding algorithm,implementations are restricted in making these functions available. Allthe functions in the Encryption Feature Groupmay therefore return [ENOSYS] or alternatively,<i><a href="encrypt.html">encrypt()</a></i>shall return [ENOSYS] for the decryption operation.<p>An implementation that claims conformance to this Feature Group shall set_XOPEN_CRYPT to a value other than -1.An implementation that does not claim conformance to this Feature Groupshall set _XOPEN_CRYPT to -1.<h4><a name = "tag_000_005_002">Realtime</a></h4>This document includes all the interfaces defined in the POSIX Realtime Extension.<p>Where entire manual pages have been added, they are marked<b>REALTIME</b>.Where additional semantics have been added to existing manual pages,the new material is identified by use of the RT margin legend.<p>An implementation that claims conformance to this Feature Group shallset the macro _XOPEN_REALTIME to a value other than -1. An implementation that does not claim conformance shall set_XOPEN_REALTIME to -1.<p>The POSIX Realtime Extension defines the following symbolic constants and their meaning:<dl compact><dt>_POSIX_ASYNCHRONOUS_IO<dd>Implementation supports the Asynchronous Input and Output option.<dt>_POSIX_FSYNC<dd>Implementation supports the File Synchronisation option.XSI-conformant systems always support the functionality associatedwith this symbol.<dt>_POSIX_MAPPED_FILES<dd>Implementation supports the Memory Mapped Files option.XSI-conformant systems always support the functionality associatedwith this symbol.<dt>_POSIX_MEMLOCK<dd>Implementation supports the Process Memory Locking option.<dt>_POSIX_MEMLOCK_RANGE<dd>Implementation supports the Range Memory Locking option.<dt>_POSIX_MEMORY_PROTECTION<dd>Implementation supports the Memory Protection option.XSI-conformant systems always support the functionality associatedwith this symbol.<dt>_POSIX_MESSAGE_PASSING<dd>Implementation supports the Message Passing option.<dt>_POSIX_PRIORITIZED_IO<dd>Implementation supports the Prioritized Input and Output option.<dt>_POSIX_PRIORITY_SCHEDULING<dd>Implementation supports the Process Scheduling option.<dt>_POSIX_REALTIME_SIGNALS<dd>Implementation supports the Realtime Signals Extension option.<dt>_POSIX_SEMAPHORES<dd>Implementation supports the Semaphores option.<dt>_POSIX_SHARED_MEMORY_OBJECTS<dd>Implementation supports the Shared Memory Objects option.<dt>_POSIX_SYNCHRONIZED_IO<dd>Implementation supports the Synchronised Input and Output option.<dt>_POSIX_TIMERS<dd>Implementation supports the Timers option.</dl><p>If the symbol _XOPEN_REALTIME is defined to have a value other than-1, then the following symbolic constants will be defined to anunspecified value:<pre><dl compact><dt> <dd>_POSIX_ASYNCHRONOUS_IO_POSIX_MEMLOCK_POSIX_MEMLOCK_RANGE_POSIX_MESSAGE_PASSING_POSIX_PRIORITY_SCHEDULING_POSIX_REALTIME_SIGNALS_POSIX_SEMAPHORES_POSIX_SHARED_MEMORY_OBJECTS_POSIX_SYNCHRONIZED_IO_POSIX_TIMERS</dl></pre><p>Interfaces in the _XOPEN_REALTIME Feature Group are marked <b>REALTIME</b>.<p>The functionality associated with _POSIX_MAPPED_FILES,_POSIX_MEMORY_PROTECTION and _POSIX_FSYNC is always present onXSI-conformant systems.<p>Support of _POSIX_PRIORITIZED_IO is optional. If this functionality issupported, then _POSIX_PRIORITIZED_IO will be set to a value other than-1. Otherwise it will be undefined.<p>If _POSIX_PRIORITIZED_IO is supported, then asynchronous I/O operationsperformed by <i><a href="aio_read.html">aio_read()</a></i>,<i><a href="aio_write.html">aio_write()</a></i>and<i><a href="lio_listio.html">lio_listio()</a></i>will be submitted at a priority equal to the scheduling priority of theprocess minus <i>aiocbp->aio_reqprio</i>. The implementation will alsodocument for which files I/O prioritization is supported.<h4><a name = "tag_000_005_003">Realtime Threads</a></h4><xref type="3" name="realtime_threads"></xref><p>The Realtime Threads Feature Group includes the interfaces covered bythe POSIX Threads compile-time symbolic constants_POSIX_THREAD_PRIO_INHERIT,_POSIX_THREAD_PRIO_PROTECTand_POSIX_THREAD_PRIORITY_SCHEDULING as defined in<i><a href="unistd.h.html"><unistd.h></a></i>.This includes the following interfaces:<pre><dl compact><dt> <dd><i><a href="pthread_attr_getinheritsched.html">pthread_attr_getinheritsched()</a></i><i><a href="pthread_attr_getschedpolicy.html">pthread_attr_getschedpolicy()</a></i><i><a href="pthread_attr_getscope.html">pthread_attr_getscope()</a></i><i><a href="pthread_attr_setinheritsched.html">pthread_attr_setinheritsched()</a></i><i><a href="pthread_attr_setschedpolicy.html">pthread_attr_setschedpolicy()</a></i><i><a href="pthread_attr_setscope.html">pthread_attr_setscope()</a></i><i><a href="pthread_getschedparam.html">pthread_getschedparam()</a></i><i><a href="pthread_mutex_getprioceiling.html">pthread_mutex_getprioceiling()</a></i><i><a href="pthread_mutex_setprioceiling.html">pthread_mutex_setprioceiling()</a></i><i><a href="pthread_mutexattr_getprioceiling.html">pthread_mutexattr_getprioceiling()</a></i><i><a href="pthread_mutexattr_getprotocol.html">pthread_mutexattr_getprotocol()</a></i><i><a href="pthread_mutexattr_setprioceiling.html">pthread_mutexattr_setprioceiling()</a></i><i><a href="pthread_mutexattr_setprotocol.html">pthread_mutexattr_setprotocol()</a></i><i><a href="pthread_setschedparam.html">pthread_setschedparam()</a></i></dl></pre><p>Where applicable, pages are marked <b>REALTIME THREADS</b>,together with the RTT margin legend for the SYNOPSIS section.<p>An implementation that claims conformance to this Feature Group shallset _XOPEN_REALTIME_THREADS to a value other than -1.An implementation that does not claim conformance to this FeatureGroup shall set the value of _XOPEN_REALTIME_THREADS to -1.<p>If the symbol _XOPEN_REALTIME_THREADS is defined to have a value otherthan -1, then the symbols:<dl compact><dt> <dd>_POSIX_THREAD_PRIORITY_SCHEDULING_POSIX_THREAD_PRIO_PROTECT_POSIX_THREAD_PRIO_INHERIT</dl></pre><p>will also be defined; otherwise these symbols will be undefined.<h4><a name = "tag_000_005_004">Legacy</a></h4><xref type="3" name="legacy"></xref><p>The Legacy Feature Group includes the interfaces and headers whichwere mandatory in previous versions of this specification but areoptional in this version of the specification.<p>These interfaces and headers are retained in this specificationbecause of their widespread use.Application writers should not rely on the existence of theseinterfaces or headers in new applications, but should follow themigration path detailed in the APPLICATION USAGE sections of therelevant pages.<p>Various factors may have contributed to the decision to mark aninterface or header <b>LEGACY</b>.In all cases, the specific reasons for the withdrawal of an interfaceor header are documented on the relevant pages.<p>Once an interface or header is marked <b>LEGACY</b>, no modifications will bemade to the specifications of such interfaces or headers other than tothe APPLICATION USAGE sections of the relevant pages.<p>The interfaces and headers which form this Feature Group are asfollows:<table bordercolor=#000000 border=1 align=center><tr valign=top><th colspan=5 align=center><b>Legacy Interfaces, Headers and External Variables</b><tr valign=top><td align=left> <a href="advance.html"><i>advance</i>()</a> <a href="brk.html"><i>brk</i>()</a> <a href="chroot.html"><i>chroot</i>()</a> <a href="compile.html"><i>compile</i>()</a> <a href="cuserid.html"><i>cuserid</i>()</a> <td align=left> <a href="gamma.html"><i>gamma</i>()</a> <a href="getdtablesize.html"><i>getdtablesize</i>()</a> <a href="getpagesize.html"><i>getpagesize</i>()</a> <a href="getpass.html"><i>getpass</i>()</a> <a href="getw.html"><i>getw</i>()</a> <td align=left> <a href="putw.html"><i>putw</i>()</a> <a href="re_comp.html"><i>re_comp</i>()</a> <a href="re_exec.html"><i>re_exec</i>()</a> <a href="regcmp.html"><i>regcmp</i>()</a> <a href="regex.html"><i>regex</i>()</a> <td align=left> <a href="sbrk.html"><i>sbrk</i>()</a> <a href="sigstack.html"><i>sigstack</i>()</a> <a href="step.html"><i>step</i>()</a> <a href="ttyslot.html"><i>ttyslot</i>()</a> <a href="valloc.html"><i>valloc</i>()</a><td align=left> <a href="wait3.html"><i>wait3</i>()</a><tr valign=top><td align=left><a href="regex.h.html"><b><regexp.h></b> </a><td align=left><a href="varargs.h.html"><b><varargs.h></b> </a><td align=left><a href="re_comp.h.html"><b><re_comp.h></b> </a><td align=left> <td align=left> <tr valign=top><td align=left><a href="loc1.html"><i>loc1</i> </a><td align=left><a href="libgen.h.html"><i>__loc1</i> </a><td align=left><a href="loc1.html"><i>loc2</i> </a><td align=left><a href="locs.html"><i>locs</i> </a><td align=left> </table></pre><p>An implementation that claims conformance to this Feature Group shallset the macro _XOPEN_LEGACY to a value other than -1. An implementation that does not claim conformance shall set_XOPEN_LEGACY to -1.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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