359 lines
10 KiB
HTML
359 lines
10 KiB
HTML
|
<!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>shmat()-Attach Shared Memory Segment to Current Process</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>shmat()--Attach Shared Memory Segment to Current Process</h2>
|
||
|
|
|
||
|
|
<div class="box" style="width: 70%;">
|
||
|
|
<br>
|
||
|
|
Syntax<br>
|
||
|
|
<pre>
|
||
|
|
#include <sys/shm.h>
|
||
|
|
|
||
|
|
void *shmat(int <em>shmid</em>, const void <em>*shmaddr</em>,
|
||
|
|
int <em>shmflg</em>);
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
Service Program Name: QP0ZUSHR<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
Default Public Authority: *USE<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
Threadsafe: Yes<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<p>The <strong>shmat()</strong> function attaches to the shared memory segment
|
||
|
|
specified by <em>shmid</em> and returns the address of the shared
|
||
|
|
memory segment.</p>
|
||
|
|
|
||
|
|
<p>The address specified by <em>shmaddr</em> is only used when <strong>
|
||
|
|
shmat()</strong> is called from a program that uses data model *LLP64 and
|
||
|
|
attaches to a teraspace shared memory segment. Otherwise the address specified
|
||
|
|
by <em>shmaddr</em> is ignored and the actual shared memory segment address
|
||
|
|
is returned regardless of the value of <em>shmaddr</em>.</p>
|
||
|
|
|
||
|
|
<p>The system maintains status information about a shared memory segment which can
|
||
|
|
be retrieved with the <a href="ipcshmct.htm">shmctl()</a> function. When a shared
|
||
|
|
memory segment is successfully attached, the system sets the members of the
|
||
|
|
<samp>shmid_ds</samp> structure as follows:<p>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li><samp>shm_nattch</samp> is incremented by 1.<p></li>
|
||
|
|
|
||
|
|
<li><samp>shm_lpid</samp> is set to the process ID of the calling thread.<p></li>
|
||
|
|
|
||
|
|
<li><samp>shm_atime</samp> is set to the current time.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Parameters</h3>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><strong>shmid</strong></dt>
|
||
|
|
|
||
|
|
<dd>(Input) Shared memory identifier, a positive integer. It is returned by the
|
||
|
|
<a href="ipcshmgt.htm">shmget()</a> function and used to identify the shared memory
|
||
|
|
segment.<br>
|
||
|
|
<br>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><strong>shmaddr</strong></dt>
|
||
|
|
|
||
|
|
<dd>(Input) Shared memory address. The address at which the calling thread
|
||
|
|
would like the shared memory segment attached.<br>
|
||
|
|
<br>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><strong>shmflg</strong></dt>
|
||
|
|
|
||
|
|
<dd>(Input) Operations flags. The value of the <em>shmflg</em> parameter is either zero
|
||
|
|
or is obtained by performing an OR operation on one or more of the
|
||
|
|
following constants:<p>
|
||
|
|
<dl>
|
||
|
|
<dt><strong>SHM_RDONLY (0x00001000)</strong></dt>
|
||
|
|
<dd>Attach the shared memory segment in read-only
|
||
|
|
mode. This flag is valid only for teraspace shared memory segments.</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Authorities</h3>
|
||
|
|
|
||
|
|
<p><strong><a name="TBLAHAT1">Authorization Required for shmat()</a></strong></p>
|
||
|
|
|
||
|
|
<table border cellpadding="5">
|
||
|
|
<!-- cols="60 20 20" -->
|
||
|
|
<tr>
|
||
|
|
<th align="left" valign="bottom">Object Referred to</th>
|
||
|
|
<th align="left" valign="bottom">Authority Required</th>
|
||
|
|
<th align="left" valign="bottom">errno</th>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">Shared memory segment to be attached in
|
||
|
|
read/write memory</td>
|
||
|
|
<td align="left" valign="top">Read and Write</td>
|
||
|
|
<td align="left" valign="top">EACCES</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top">Shared memory segment to be attached in read-only
|
||
|
|
memory in a process's teraspace.</td>
|
||
|
|
<td align="left" valign="top">Read</td>
|
||
|
|
<td align="left" valign="top">EACCES</td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Return Value</h3>
|
||
|
|
|
||
|
|
<table cellpadding="5">
|
||
|
|
<!-- cols="15 85" -->
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top"><em>value</em></td>
|
||
|
|
<td align="left" valign="top"><strong>shmat()</strong> was successful. The
|
||
|
|
value returned is a pointer to the shared memory segment associated with the
|
||
|
|
specified identifier.</td>
|
||
|
|
</tr>
|
||
|
|
|
||
|
|
<tr>
|
||
|
|
<td align="left" valign="top"><em>NULL</em></td>
|
||
|
|
<td align="left" valign="top"><strong>shmat()</strong> was not successful. The
|
||
|
|
<em>errno</em> variable is set to indicate the error.</td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Error Conditions</h3>
|
||
|
|
|
||
|
|
<p>If <strong>shmat()</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>[EACCES]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>Permission denied.</p>
|
||
|
|
|
||
|
|
<p>An attempt was made to access an object in a way forbidden by its object
|
||
|
|
access permissions.</p>
|
||
|
|
|
||
|
|
<p>The thread does not have access to the specified file, directory, component,
|
||
|
|
or path.</p>
|
||
|
|
|
||
|
|
<p>Operation permission is denied to the calling thread.</p>
|
||
|
|
|
||
|
|
<p>Shared memory operations are not permitted because the QSHRMEMCTL system
|
||
|
|
value is set to 0.</p>
|
||
|
|
|
||
|
|
<p>The shared memory segment is to be attached in read/write mode and the calling
|
||
|
|
thread does not read and write permission to the shared memory segment.</p>
|
||
|
|
|
||
|
|
<p>The shared memory segment is to be attached in read-only mode and the calling
|
||
|
|
thread does not read permission to the shared memory segment.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><em>[EADDRINUSE]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>A damaged object was encountered.</p>
|
||
|
|
|
||
|
|
<p>Address already in use.</p>
|
||
|
|
|
||
|
|
<p>An attempt was made to attach to a teraspace shared memory segment with the
|
||
|
|
SHM_MAP_FIXED_NP attribute and the address range is not available in the
|
||
|
|
teraspace of the current job.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><em>[EDAMAGE]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>A damaged object was encountered.</p>
|
||
|
|
|
||
|
|
<p>The shared memory segment has been damaged by a previous shared memory
|
||
|
|
operation.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><em>[EFAULT]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>The address used for an argument is not correct.</p>
|
||
|
|
|
||
|
|
<p>In attempting to use an argument in a call, the system detected an address
|
||
|
|
that is not valid.</p>
|
||
|
|
|
||
|
|
<p>While attempting to access a parameter passed to this function, the system
|
||
|
|
detected an address that is not valid.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<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>
|
||
|
|
|
||
|
|
<p>The <em>shmid</em> parameter is not a valid shared memory identifier.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><em>[EOPNOTSUPP]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>Operation not supported.</p>
|
||
|
|
|
||
|
|
<p>The operation, though supported in general, is not supported for the
|
||
|
|
requested object or the requested arguments.</p>
|
||
|
|
|
||
|
|
<p>The SHM_RDONLY flag is set in the <em>shmflg</em> parameter.
|
||
|
|
Read-only shared memory segments are not supported for
|
||
|
|
nonteraspace shared memory segments and for shared memory segments
|
||
|
|
created with the SHM_MAP_FIXED_NP attribute.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><em>[ENOMEM]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>Storage allocation request failed.</p>
|
||
|
|
|
||
|
|
<p>A function needed to allocate storage, but no storage is available.</p>
|
||
|
|
|
||
|
|
<p>The available data space is not large enough to accommodate the shared
|
||
|
|
memory segment.</p>
|
||
|
|
</dd>
|
||
|
|
|
||
|
|
<dt><em>[EUNKNOWN]</em></dt>
|
||
|
|
|
||
|
|
<dd>
|
||
|
|
<p>Unknown system state.</p>
|
||
|
|
|
||
|
|
<p>The operation failed because of an unknown system state. See any messages in
|
||
|
|
the job log and correct any errors that are indicated, then retry the
|
||
|
|
operation.</p>
|
||
|
|
</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Error Messages</h3>
|
||
|
|
|
||
|
|
<p>None.</p>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3><a name="USAGE_NOTES">Usage Notes</a></h3>
|
||
|
|
|
||
|
|
<ol>
|
||
|
|
<li>The only supported operation flag is SHM_RDONLY. This operation flag is
|
||
|
|
supported only when you attach to a teraspace shared memory segment. If <em>
|
||
|
|
shmflg</em> specifies SHM_RDONLY for a nonteraspace shared memory segment,
|
||
|
|
then an [EOPNOTSUPP] error is returned. All other values for <em>shmflg</em>
|
||
|
|
are ignored.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>A module that was not created with teraspace memory enabled should not
|
||
|
|
attach to a teraspace shared memory segment. The call to <em>shmat()</em>
|
||
|
|
will succeed and return a pointer. Any attempt, however, by a module not
|
||
|
|
created with teraspace memory enabled to use the returned pointer will result
|
||
|
|
in an MCH3601 (Pointer not set for location referenced) exception.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>When a job attaches to a shared memory segment that was created with the
|
||
|
|
SHM_MAP_FIXED_NP attribute, an address range within the job's teraspace is used for
|
||
|
|
the shared memory mapping. When a subsequent job attaches to the shared
|
||
|
|
memory segment, the same address range within its teraspace must be available.
|
||
|
|
If the address range is not available, the call to <em>shmat()</em> will fail
|
||
|
|
with an [EADDRINUSE] error.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>The storage for a shared memory segment is allocated when the first job
|
||
|
|
attaches to the shared memory segment. The storage is charged against the
|
||
|
|
job's temporary storage limit. If the job does not have enough
|
||
|
|
temporary storage to satisfy the request, the call to <em>shmat()</em> will
|
||
|
|
fail with an [ENOMEM] error.</li>
|
||
|
|
</ol>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Related Information</h3>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>The <<strong>sys/shm.h</strong>> file (see <a href="unix13.htm">
|
||
|
|
Header Files for UNIX-Type Functions</a>)<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ipcshmat.htm">shmctl()</a>--Perform Shared Memory Control
|
||
|
|
Operations<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ipcshmgt.htm">shmget()</a>--Get ID of Shared Memory Segment with
|
||
|
|
Key<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ipcshmdt.htm">shmdt()</a>--Detach Shared Memory Segment from
|
||
|
|
Calling Process</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>For an example of using this function, see <a href="../apiref/apiexusmem.htm">
|
||
|
|
Using Semaphores and Shared Memory</a> in Examples: APIs.</p>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<hr>
|
||
|
|
API introduced: V3R6
|
||
|
|
|
||
|
|
<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>
|
||
|
|
|