<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation"> <title>sem_post_np()-Post Value to Semaphore</title> <!-- Begin Header Records ========================================== --> <!-- All rights reserved. Licensed Materials Property of IBM --> <!-- US Government Users Restricted Rights --> <!-- Use, duplication or disclosure restricted by --> <!-- GSA ADP Schedule Contract with IBM Corp. --> <!-- Change History: --> <!-- YYMMDD USERID Change description --> <!-- Direct1 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 --> <!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 --> <!-- Edited by Kersten Feb 02 --> <!-- This file has undergone html cleanup on 05/01/02 by JET --> <link rel="stylesheet" type="text/css" href="../rzahg/ic.css"> </head> <body> <!--End Header Records --> <!-- Java sync-link --> <script type="text/javascript" language="Javascript" src="../rzahg/synch.js"> </script> <a name="Top_Of_Page"></a> <h2>sem_post_np()--Post Value to Semaphore</h2> <div class="box" style="width: 70%;"> <br> Syntax<br> <pre> #include <semaphore.h> int sem_post_np(sem_t * <em>sem</em>, sem_post_options_np_t *<em>options</em>); </pre> <br> Service Program Name: QP0ZPSEM<br> <!-- iddvc RMBR --> <br> Default Public Authority: *USE<br> <!-- iddvc RMBR --> <br> Threadsafe: Yes<br> <!-- iddvc RMBR --> <br> </div> <p>The <strong>sem_post_np()</strong> function posts to a semaphore, incrementing its value by the increment specified in the <em>options</em> parameter. If the resulting value is greater than zero and if there are threads waiting on the semaphore, the waiting threads decrement the semaphore and continue running.</p> <br> <h3>Parameters</h3> <dl> <dt><strong>sem</strong></dt> <dd>(Input) A pointer to an initialized unnamed semaphore or opened named semaphore.<br> <br> </dd> <dt><strong>options</strong></dt> <dd>(Input) Post options. <p>The members of the sem_post_options_np_t structure are as follows.</p> <table cellpadding="5"> <!-- cols="25 75" --> <tr> <td align="left" valign="top" nowrap><em>unsigned int reserved1[1]</em></td> <td align="left" valign="top">A reserved field that must be set to zero.</td> </tr> <tr> <td align="left" valign="top"><em>unsigned int increment</em></td> <td align="left" valign="top">The value, greater than zero, used to increment the semaphore. If the value specified causes the value of a semaphore to exceed its maximum value, <strong>sem_post_np()</strong> will fail by returning [EINVAL].</td> </tr> <tr> <td align="left" valign="top"><em>unsigned int reserved2[2]</em></td> <td align="left" valign="top">A reserved field that must be set to zero.</td> </tr> </table> </dd> </dl> <br> <h3>Authorities</h3> <p>None</p> <br> <h3>Return Value</h3> <table cellpadding="5"> <!-- cols="5 95" --> <tr> <td align="left" valign="top"><em>0</em></td> <td align="left" valign="top"><strong>sem_post_np()</strong> was successful.</td> </tr> <tr> <td align="left" valign="top"><em>-1</em></td> <td align="left" valign="top"><strong>sem_post_np()</strong> was not successful. The <em>errno</em> variable is set to indicate the error.</td> </tr> </table> <br> <br> <h3>Error Conditions</h3> <p>If <strong>sem_post_np()</strong> is not successful, <em>errno</em> usually indicates one of the following errors. Under some conditions, <em> errno</em> could indicate an error other than those listed here.</p> <dl> <dt><em>[EINVAL]</em></dt> <dd> <p>The value specified for the argument is not correct.</p> <p>A function was passed incorrect argument values, or an operation was attempted on an object and the operation specified is not supported for that type of object.</p> <p>An argument value is not valid, out of range, or NULL.</p> </dd> <dt><em>[EOVERFLOW]</em></dt> <dd> <p>Maximum value exceeded.</p> <p>Posting to the semaphore would cause its value to exceed its maximum value. The maximum value is SEM_VALUE_MAX or was set using <strong> sem_open_np()</strong> or <strong>sem_init_np()</strong>.</p> <p>The reserved fields of the <em>attr</em> argument are not set to zero.</p> </dd> </dl> <br> <h3>Error Messages</h3> <p>None.</p> <br> <h3>Related Information</h3> <ul> <li>The <<strong>semaphore.h</strong>> file (see <a href="unix13.htm"> Header Files for UNIX-Type Functions</a>)<br> <br> </li> <li><a href="ipcsemcl.htm">sem_close()</a>--Close Named Semaphore<br> <br> </li> <li><a href="ipcsemde.htm">sem_destroy()</a>--Destroy Unnamed Semaphore<br> <br> </li> <li><a href="ipcsemge.htm">sem_getvalue()</a>--Get Semaphore Value<br> <br> </li> <li><a href="ipcsemi.htm">sem_init()</a>--Initialize Unnamed Semaphore<br> <br> </li> <li><a href="ipcsemin.htm">sem_init_np()</a>--Initialize Unnamed Semaphore with Maximum Value<br> <br> </li> <li><a href="ipcsemo.htm">sem_open()</a>--Open Named Semaphore<br> <br> </li> <li><a href="ipcsemon.htm">sem_open_np()</a>--Open Named Semaphore with Maximum Value<br> <br> </li> <li><a href="ipcsemp.htm">sem_post()</a>--Post to Semaphore<br> <br> </li> <li><a href="ipcsemtr.htm">sem_trywait()</a>--Try to Decrement Semaphore<br> <br> </li> <li><a href="ipcsemun.htm">sem_unlink()</a>--Unlink Named Semaphore<br> <br> </li> <li><a href="ipcsemw.htm">sem_wait()</a>--Wait for Semaphore<br> <br> </li> <li><a href="ipcsemwn.htm">sem_wait_np()</a>--Wait for Semaphore with Timeout</li> </ul> <br> <h3>Example</h3> <p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a> for information pertaining to code examples.</p> <p>The following example initializes an unnamed semaphore and posts to it, incrementing its value by 2.</p> <pre> #include <stdio.h> #include <semaphore.h> main() { sem_t my_semaphore; sem_post_options_np_t options; int value; sem_init(&my_semaphore, 0, 10); sem_getvalue(&my_semaphore, &value); printf("The initial value of the semaphore is %d.\n", value); memset(&options, 0, sizeof(options)); options.increment=2; sem_post_np(&my_semaphore,&options); sem_getvalue(&my_semaphore, &value); printf("The value of the semaphore after the post is %d.\n", value); } </pre> <br> <h3>Output:</h3> <pre> The initial value of the semaphore is 10. The value of the semaphore after the post is 12. </pre> <br> <hr> API introduced: V4R4 <hr> <center> <table cellpadding="2" cellspacing="2"> <tr align="center"> <td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href= "unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td> </tr> </table> </center> </body> </html>