249 lines
6.3 KiB
HTML
249 lines
6.3 KiB
HTML
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>sem_unlink()--Unlink Named Semaphore</title>
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<a name="Top_Of_Page"></a>
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<h2>sem_unlink()--Unlink Named Semaphore</h2>
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<div class="box" style="width: 60%;">
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<br>
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Syntax
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<pre>
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#include <semaphore.h>
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int sem_unlink(const char *<em>name</em>);
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</pre>
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<br>
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Service Program Name: QP0ZPSEM<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>sem_unlink()</strong> function unlinks a named semaphore. The
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name of the semaphore is removed from the set of names used by named
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semaphores. If the semaphore is still in use, the semaphore is not deleted
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until all processes using the semaphore have ended or have called <strong>
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sem_close()</strong>. Using the name of an unlinked semaphore in subsequent
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calls to <strong>sem_open()</strong> or <strong>sem_open_np()</strong> will
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result in the creation of a new semaphore with the same name if the O_CREAT
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flag of the <em>oflag</em> parameter has been set.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>name</strong></dt>
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<dd>(Input) A pointer to the null-terminated name of the semaphore to be
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unlinked. The name should begin with a slash ('/') character. If the name does
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not begin with a slash ('/') character, the system adds a slash to the
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beginning of the name.
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<p>This parameter is assumed to be represented in the coded character set
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identifier (CCSID) currently in effect for the job. If the CCSID of the job is
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65535, this parameter is assumed to be represented in the default CCSID of the
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job.</p>
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<p>The name is present in a set of names used only by named semaphores. The
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name has no relation to any file system path names. The maximum length of the
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name is SEM_NAME_MAX.</p>
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<p>See <a href="ipcsemunu.htm">QlgSem_unlink()</a>--Unlink Named Semaphore
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(using NLS-enabled path name) for a description and an example of supplying the
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<em>name</em> in any CCSID.</p>
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</dd>
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</dl>
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<br>
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<h3>Authorities</h3>
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<p><strong><a name="TBLASEMU1">Authorization required for
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sem_unlink()</a></strong></p>
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<table border cellpadding="5">
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<!-- cols="60 20 20" -->
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<tr>
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<th align="left" valign="bottom">Object Referred to</th>
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<th align="left" valign="bottom">Authority Required</th>
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<th align="left" valign="bottom">errno</th>
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</tr>
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<tr>
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<td align="left" valign="top">Named semaphore to be deleted</td>
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<td align="left" valign="top">See note</td>
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<td align="left" valign="top">EACCES</td>
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</tr>
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</table>
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<p><strong>Note:</strong> To unlink a named semaphore, the effective UID of the
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process must be the creator of the semaphore or the process must have *ALLOBJ
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authority.</p>
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<br>
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<h3>Return Value</h3>
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<table cellpadding="5">
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<!-- cols="5 95" -->
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<tr>
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<td align="left" valign="top"><em>0</em></td>
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<td align="left" valign="top"><strong>sem_unlink()</strong> was
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successful.</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>-1</em></td>
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<td align="left" valign="top"><strong>sem_unlink()</strong> was not successful.
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The <em>errno</em> variable is set to indicate the error.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3><a name="ecsemun">Error Conditions</a></h3>
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<p>If <strong>sem_unlink()</strong> is not successful, <em>errno</em> usually
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indicates one of the following errors. Under some conditions, <em>errno</em>
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could indicate an error other than those listed here.</p>
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<dl>
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<dt><em>[EACCES]</em></dt>
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<dd>
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<p>Permission denied.</p>
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<p>An attempt was made to access an object in a way forbidden by its object
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access permissions.</p>
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</dd>
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<dt><em>[ENOENT]</em></dt>
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<dd>
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<p>No such path or directory.</p>
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<p>The specified name doesnot refer to an existing named semaphore.</p>
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</dd>
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<dt><em>[EFAULT]</em></dt>
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<dd>
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<p>The address used for an argument is not correct.</p>
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<p>In attempting to use an argument in a call, the system detected an address
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that is not valid.</p>
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<p>While attempting to access a parameter passed to this function, the system
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detected an address that is not valid.</p>
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</dd>
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<dt><em>[ENAMETOOLONG]</em></dt>
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<dd>
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<p>The name is too long. The name is longer than the SEM_NAME_MAX
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characters.</p>
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</dd>
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</dl>
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<br>
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<h3>Error Messages</h3>
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<p>None.</p>
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<br>
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<h3><a name="risemun">Related Information</a></h3>
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<ul>
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<li>The <<strong>semaphore.h</strong>> file (see <a href="unix13.htm">
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Header Files for UNIX-Type Functions</a>)<br>
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<br>
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</li>
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<li><a href="ipcsemunu.htm">QlgSem_unlink()</a>--Unlink Named Semaphore (using
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NLS-enabled path name)<br>
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<br>
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</li>
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<li><a href="ipcsemo.htm">sem_open()</a>--Open Named Semaphore<br>
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<br>
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</li>
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<li><a href="ipcsemon.htm">sem_open_np()</a>--Open Named Semaphore with Maximum
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Value</li>
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</ul>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<p>The following example unlinks the named semaphore "/mysem".</p>
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<pre>
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#include <semaphore.h>
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main() {
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int rc;
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rc = sem_unlink("/mysem");
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}
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</pre>
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<br>
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<hr>
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API introduced: V4R4
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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