563 lines
14 KiB
HTML
563 lines
14 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>ftok()--Generate IPC Key from File Name</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 -->
|
|
<!-- 020618 EMIG: updated for NFS threadsafety, V5R3 -->
|
|
<!-- 020719 MFENLON: updated for QFileSvr.400 threadsafety, V5R3 -->
|
|
<!-- End Header Records -->
|
|
<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
|
|
</head>
|
|
<body>
|
|
<!-- Java sync-link -->
|
|
<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
|
|
</script>
|
|
|
|
<a name="Top_Of_Page"></a>
|
|
|
|
<h2>ftok()--Generate IPC Key from File Name</h2>
|
|
|
|
<div class="box" style="width: 60%;">
|
|
<br>
|
|
Syntax<br>
|
|
<pre>
|
|
#include <sys/ipc.h>
|
|
|
|
key_t ftok(const char <em>*path</em>, int <em>id</em>);
|
|
</pre>
|
|
|
|
<br>
|
|
Service Program Name: QP0ZCPA<br>
|
|
<!-- iddvc RMBR -->
|
|
<br>
|
|
Default Public Authority: *USE<br>
|
|
<!-- iddvc RMBR -->
|
|
<br>
|
|
Threadsafe: Conditional; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
|
|
<!-- iddvc RMBR -->
|
|
<br>
|
|
</div>
|
|
|
|
<p>The <strong>ftok()</strong> function generates an IPC key based on the
|
|
combination of <em>path</em> and <em>id</em>.</p>
|
|
|
|
<p>Identifier-based interprocess communication facilities require you to supply
|
|
a key to the <strong>msgget()</strong>, <strong>semget()</strong>, <strong>
|
|
shmget()</strong> subroutines to obtain interprocess communication identifiers.
|
|
The <strong>ftok()</strong> function is one mechanism to generate these
|
|
keys.</p>
|
|
|
|
<p>If the values for <em>path</em> and <em>id</em> are the same as a previous
|
|
call to <strong>ftok()</strong> and the file named by <em>path</em> was not
|
|
deleted and re-created in between calls to <strong>ftok()</strong>, <strong>
|
|
ftok()</strong> will return the same key.</p>
|
|
|
|
<p>The <strong>ftok()</strong> function returns different keys if different
|
|
values of <em>path</em> and <em>id</em> are used.</p>
|
|
|
|
<p>Only the low-order 8-bits of <em>id</em> are significant. The remaining bits
|
|
are ignored by <strong>ftok()</strong>.</p>
|
|
|
|
<br>
|
|
<h3>Parameters</h3>
|
|
|
|
<dl>
|
|
<dt><strong>path</strong></dt>
|
|
|
|
<dd>(Input) The path name of the file used in combination with <em>id</em> to
|
|
generate the key.
|
|
|
|
<p>See <a href="p0zftoku.htm">QlgFtok--Generate IPC Key from File Name (using
|
|
NLS-enabled path name)</a> for a description and an example of supplying the
|
|
<em>path</em> in any CCSID.</p>
|
|
</dd>
|
|
|
|
<dt><strong>id</strong></dt>
|
|
|
|
<dd>(Input) The integer identifier used in combination with <em>path</em> to
|
|
generate the key. Only the low order 8-bits of <em>id</em> are significant. The
|
|
remaining bits will be ignored.</dd>
|
|
</dl>
|
|
|
|
<br>
|
|
<h3>Authorities</h3>
|
|
|
|
<p><strong><a name="TBLASTAT1">Authorization Required for ftok() (excluding
|
|
QOPT)</a></strong></p>
|
|
|
|
<table border width="80%" 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">Each directory in the path name preceding the
|
|
object</td>
|
|
<td align="left" valign="top">*X</td>
|
|
<td align="left" valign="top">EACCES</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left" valign="top">Object</td>
|
|
<td align="left" valign="top">None</td>
|
|
<td align="left" valign="top">None</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<br>
|
|
<br>
|
|
|
|
|
|
<p><strong><a name="TBLASTAT4">Authorization Required for ftok() in the QOPT
|
|
File System</a></strong></p>
|
|
|
|
<table border width="80%" 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">Volume containing directory or object</td>
|
|
<td align="left" valign="top">*USE</td>
|
|
<td align="left" valign="top">EACCES</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left" valign="top">Directory or object within volume</td>
|
|
<td align="left" valign="top">None</td>
|
|
<td align="left" valign="top">None</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<br>
|
|
<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>ftok()</strong> was successful.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left" valign="top"><em>(key_t)-1</em></td>
|
|
<td align="left" valign="top"><strong>ftok()</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>ftok()</strong> is not successful, <em>errno</em> indicates one
|
|
of the following errors.</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>If you are accessing a remote file through the Network File System, update
|
|
operations to file permissions at the server are not reflected at the client
|
|
until updates to data that is stored locally by the Network File System take
|
|
place. (Several options on the Add Mounted File System (ADDMFS) command
|
|
determine the time between refresh operations of local data.) Access to a
|
|
remote file may also fail due to different mappings of user IDs (UID) or group
|
|
IDs (GID) on the local and remote systems.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EAGAIN]</em></dt>
|
|
|
|
<dd>
|
|
<p>Operation would have caused the process to be suspended.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EBADFID]</em></dt>
|
|
|
|
<dd>
|
|
<p>A file ID could not be assigned when linking an object to a directory.</p>
|
|
|
|
<p>The file ID table is missing or damaged.</p>
|
|
|
|
<p>To recover from this error, run the Reclaim Storage (RCLSTG) command as soon
|
|
as possible.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EBADNAME]</em></dt>
|
|
|
|
<dd>
|
|
<p>The object name specified is not correct.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EBUSY]</em></dt>
|
|
|
|
<dd>
|
|
<p>Resource busy.</p>
|
|
|
|
<p>An attempt was made to use a system resource that is not available at this
|
|
time.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ECONVERT]</em></dt>
|
|
|
|
<dd>
|
|
<p>Conversion error.</p>
|
|
|
|
<p>One or more characters could not be converted from the source CCSID to the
|
|
target CCSID.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EDAMAGE]</em></dt>
|
|
|
|
<dd>
|
|
<p>A damaged object was encountered.</p>
|
|
|
|
<p>A referenced object is damaged. The object cannot be used.</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>[EFILECVT]</em></dt>
|
|
|
|
<dd>
|
|
<p>File ID conversion of a directory failed.</p>
|
|
|
|
<p>Try to run the Reclaim Storage (RCLSTG) command to recover from this
|
|
error.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EINTR]</em></dt>
|
|
|
|
<dd>
|
|
<p>Interrupted function call.</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>
|
|
</dd>
|
|
|
|
<dt><em>[EIO]</em></dt>
|
|
|
|
<dd>
|
|
<p>Input/output error.</p>
|
|
|
|
<p>A physical I/O error occurred.</p>
|
|
|
|
<p>A referenced object may be damaged.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ELOOP]</em></dt>
|
|
|
|
<dd>
|
|
<p>A loop exists in the symbolic links.</p>
|
|
|
|
<p>This error is issued if the number of symbolic links encountered is more
|
|
than POSIX_SYMLOOP (defined in the limits.h header file). Symbolic links are
|
|
encountered during resolution of the directory or path name.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ENAMETOOLONG]</em></dt>
|
|
|
|
<dd>
|
|
<p>A path name is too long.</p>
|
|
|
|
<p>A path name is longer than PATH_MAX characters or some component of the name
|
|
is longer than NAME_MAX characters while _POSIX_NO_TRUNC is in effect. For
|
|
symbolic links, the length of the name string substituted for a symbolic link
|
|
exceeds PATH_MAX. The PATH_MAX and NAME_MAX values can be determined using the
|
|
<strong>pathconf()</strong> function.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ENOENT]</em></dt>
|
|
|
|
<dd>
|
|
<p>No such path or directory.</p>
|
|
|
|
<p>The directory or a component of the path name specified does not exist.</p>
|
|
|
|
<p>A named file or directory does not exist or is an empty string.</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>There is not enough memory to perform the requested function.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ENOSPC]</em></dt>
|
|
|
|
<dd>
|
|
<p>No space available.</p>
|
|
|
|
<p>The requested operations required additional space on the device and there
|
|
is no space left. This could also be caused by exceeding the user profile
|
|
storage limit when creating or transferring ownership of an object.</p>
|
|
|
|
<p>Insufficient space remains to hold the intended file, directory, or
|
|
link.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ENOTDIR]</em></dt>
|
|
|
|
<dd>
|
|
<p>Not a directory.</p>
|
|
|
|
<p>A component of the specified path name existed, but it was not a directory
|
|
when a directory was expected.</p>
|
|
|
|
<p>Some component of the path name is not a directory, or is an empty
|
|
string.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ENOTSAFE]</em></dt>
|
|
|
|
<dd>
|
|
<p>Function is not allowed in a job that is running with multiple threads.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ENOTSUP]</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>
|
|
</dd>
|
|
|
|
<dt><em>[EPERM]</em></dt>
|
|
|
|
<dd>
|
|
<p>Operation not permitted.</p>
|
|
|
|
<p>You must have appropriate privileges or be the owner of the object or other
|
|
resource to do the requested operation.</p>
|
|
</dd>
|
|
|
|
<dt><em>[EROOBJ]</em></dt>
|
|
|
|
<dd>
|
|
<p>Object is read only.</p>
|
|
|
|
<p>You have attempted to update an object that can be read only.</p>
|
|
</dd>
|
|
|
|
<dt><em>[ESTALE]</em></dt>
|
|
|
|
<dd>
|
|
<p>File or object handle rejected by server.</p>
|
|
|
|
<p>If you are accessing a remote file through the Network File System, the file
|
|
may have been deleted at the server.</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><a name="USAGE_NOTES">Usage Notes</a></h3>
|
|
|
|
<ol>
|
|
<li>This function will fail with error code [ENOTSAFE] when both of the
|
|
following conditions occur:<br>
|
|
<br>
|
|
<ul>
|
|
<li>Where multiple threads exist in the job.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>The object this function is operating on resides in a file system that is
|
|
not threadsafe. Only the following file systems are threadsafe for this
|
|
function:<br>
|
|
<br>
|
|
<ul>
|
|
<li>Root</li>
|
|
|
|
<li>QOpenSys</li>
|
|
|
|
<li>User-defined</li>
|
|
|
|
<li>QNTC</li>
|
|
|
|
<li>QSYS.LIB</li>
|
|
|
|
<li>Independent ASP QSYS.LIB</li>
|
|
|
|
<li>QOPT</li>
|
|
|
|
<li>Network File System</li>
|
|
|
|
|
|
<li>QFileSvr.400</li>
|
|
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
|
|
<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>If the values for <em>path</em> and <em>id</em> are the same as a previous
|
|
call to <strong>ftok()</strong> and if the file named by <em>path</em> was
|
|
deleted and re-created in between calls to <strong>ftok()</strong>, <strong>
|
|
ftok()</strong> will return a different key.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>The <strong>ftok()</strong> function will return the same key for different
|
|
values of <em>path</em> if the path names refer to symbolic links or hard links
|
|
whose target files are the same.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>The <strong>ftok()</strong> function may return the same key for different
|
|
values of <em>path</em> if the target files are in different file systems.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>The <strong>ftok()</strong> function may return the same key for different
|
|
values of <em>path</em> if the target file is in a file system that contains
|
|
more than 2<sup>24</sup> files.</li>
|
|
</ol>
|
|
|
|
<br>
|
|
<h3>Related Information</h3>
|
|
|
|
<ul>
|
|
<li><a href="p0zftoku.htm">QlgFtok</a>--Generate IPC Key from File Name (using
|
|
NLS-enabled path name)<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="ipcmsggt.htm">msgget()</a>--Get Message Queue<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="ipcsemgt.htm">semget()</a>--Get Semaphore Set with Key<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="ipcshmgt.htm">shmget()</a>--Get ID of Shared Memory Segment with
|
|
Key</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 uses <strong>ftok()</strong> and <strong>
|
|
semget()</strong> functions.</p>
|
|
|
|
<pre>
|
|
#include <sys/ipc.h>
|
|
#include <sys/sem.h>
|
|
#include <errno.h>
|
|
#include <stdio.h>
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
key_t myKey;
|
|
int semid;
|
|
|
|
/* Use ftok to generate a key associated with a file. */
|
|
/* Every process will get the same key back if the */
|
|
/* caller calls with the same parameters. */
|
|
myKey = ftok("/myApplication/myFile", 42);
|
|
if(myKey == -1) {
|
|
printf("ftok failed with errno = %d\n", errno);
|
|
return -1;
|
|
}
|
|
|
|
/* Call an xxxget() API, where xxx is sem, shm, or msg. */
|
|
/* This will create or reference an existing IPC object */
|
|
/* with the 'well known' key associated with the file */
|
|
/* name used above. */
|
|
semid = semget(myKey, 1, 0666 | IPC_CREAT);
|
|
if(semid == -1) {
|
|
printf("semget failed with errno = %d\n", errno);
|
|
return -1;
|
|
}
|
|
|
|
/* ... Use the semaphore as required ... */
|
|
return 0;
|
|
}
|
|
</pre>
|
|
|
|
<br>
|
|
<hr>
|
|
API introduced: V4R3
|
|
|
|
<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>
|
|
|