154 lines
5.7 KiB
HTML
154 lines
5.7 KiB
HTML
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<title>shm_unlink</title>
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<basefont size="3"> <a name="shm_unlink"></a> <a name="tag_03_674"></a><!-- shm_unlink -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_674_01"></a>NAME</h4>
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<blockquote>shm_unlink - remove a shared memory object (<b>REALTIME</b>)</blockquote>
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<h4><a name="tag_03_674_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('SHM')">SHM</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/sys/mman.h.html">sys/mman.h</a>><br>
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<br>
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int shm_unlink(const char *</tt><i>name</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_674_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>shm_unlink</i>() function shall remove the name of the shared memory object named by the string pointed to by
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<i>name</i>.</p>
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<p>If one or more references to the shared memory object exist when the object is unlinked, the name shall be removed before
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<i>shm_unlink</i>() returns, but the removal of the memory object contents shall be postponed until all open and map references to
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the shared memory object have been removed.</p>
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<p>Even if the object continues to exist after the last <i>shm_unlink</i>(), reuse of the name shall subsequently cause <a href=
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"../functions/shm_open.html"><i>shm_open</i>()</a> to behave as if no shared memory object of this name exists (that is, <a href=
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"../functions/shm_open.html"><i>shm_open</i>()</a> will fail if O_CREAT is not set, or will create a new shared memory object if
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O_CREAT is set).</p>
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</blockquote>
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<h4><a name="tag_03_674_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, a value of zero shall be returned. Otherwise, a value of -1 shall be returned and <i>errno</i> set
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to indicate the error. If -1 is returned, the named shared memory object shall not be changed by this function call.</p>
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</blockquote>
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<h4><a name="tag_03_674_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>shm_unlink</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EACCES]</dt>
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<dd>Permission is denied to unlink the named shared memory object.</dd>
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<dt>[ENAMETOOLONG]</dt>
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<dd>
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The length of the <i>name</i> argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.</dd>
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<dt>[ENOENT]</dt>
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<dd>The named shared memory object does not exist.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_674_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_674_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Names of memory objects that were allocated with <a href="../functions/open.html"><i>open</i>()</a> are deleted with <a href=
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"../functions/unlink.html"><i>unlink</i>()</a> in the usual fashion. Names of memory objects that were allocated with <a href=
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"../functions/shm_open.html"><i>shm_open</i>()</a> are deleted with <i>shm_unlink</i>(). Note that the actual memory object is not
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destroyed until the last close and unmap on it have occurred if it was already in use.</p>
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</blockquote>
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<h4><a name="tag_03_674_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_674_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_674_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="close.html"><i>close</i>()</a> , <a href="mmap.html"><i>mmap</i>()</a> , <a href="munmap.html"><i>munmap</i>()</a> , <a
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href="shmat.html"><i>shmat</i>()</a> , <a href="shmctl.html"><i>shmctl</i>()</a> , <a href="shmdt.html"><i>shmdt</i>()</a> , <a
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href="shm_open.html"><i>shm_open</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/sys/mman.h.html"><i><sys/mman.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_674_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p>
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</blockquote>
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<h4><a name="tag_03_674_12"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>shm_unlink</i>() function is marked as part of the Shared Memory Objects option.</p>
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<p>In the DESCRIPTION, text is added to clarify that reusing the same name after a <i>shm_unlink</i>() will not attach to the old
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shared memory object.</p>
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<p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Shared
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Memory Objects option.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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