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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
<title>sysconf()--Get System Configuration Variables</title>
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<h2>sysconf()--Get System Configuration Variables</h2>
<div class="box" style="width: 60%;">
<br>
&nbsp;&nbsp;Syntax<br>
<pre>
#include &lt;unistd.h&gt;
long sysconf(int <strong>name</strong>);
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QP0LLIB1<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Threadsafe: Yes<br>
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<br>
</div>
<p>The <strong>sysconf()</strong> function returns the value of a system
configuration option. The configuration option to be obtained is specified by
<strong>name</strong>.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt><strong><em>name</em></strong></dt>
<dd>(Input) The named variable whose value is to be returned.</dd>
</dl>
<p>The value of <strong>name</strong> can be any one of the following symbols
defined in the &lt;<strong>unistd.h</strong>&gt; header file, each
corresponding to a system configuration option:</p>
<table cellpadding="5">
<!-- cols="25 75" -->
<tr>
<td align="left" valign="top"><em>_SC_ARG_MAX</em></td>
<td align="left" valign="top">(Not supported by the iSeries server). Represents
ARG_MAX, which indicates the maximum number of bytes of arguments and
environment data that can be passed in an <strong>exec</strong> function.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_CHILD_MAX</em></td>
<td align="left" valign="top">(Not supported by the iSeries server). Represents
CHILD_MAX, which indicates the maximum number of jobs that a real user ID (UID)
can have running simultaneously.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_CLK_TCK</em></td>
<td align="left" valign="top">Represents the CLK_TCK macro, which indicates the
number of clock ticks in a second. CLK_TCK is defined in the
&lt;<strong>time.h</strong>&gt; header file.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_JOB_CONTROL</em></td>
<td align="left" valign="top">(Not supported by the iSeries server). Represents
the _POSIX_JOB_CONTROL macro, which indicates that certain job control
operations are implemented by this version of the operating system. If
_POSIX_JOB_CONTROL is defined (in the &lt;<strong>unistd.h</strong>&gt; header
file), various APIs, such as <strong>setpgid()</strong>, provide more function
than when the macro is not defined.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_NGROUPS_MAX</em></td>
<td align="left" valign="top">Represents NGROUPS_MAX, which indicates the
maximum number of supplementary group IDs (GIDs) that can be associated with a
job.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_OPEN_MAX</em></td>
<td align="left" valign="top">Represents OPEN_MAX, which indicates the maximum
number of files that a single job can have open at one time.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_PAGESIZE</em></td>
<td align="left" valign="top">Represents the system hardware page size. The
symbol _SC_PAGESIZE is defined as the decimal value 11.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_PAGE_SIZE</em></td>
<td align="left" valign="top">Represents the system hardware page size. The
symbol _SC_PAGE_SIZE is defined as the decimal value 12.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_SAVED_IDS</em></td>
<td align="left" valign="top">(Not supported by the iSeries server). Represents
the _POSIX_SAVED_IDS macro, which indicates that this POSIX implementation has
a saved set UID and a saved set GID. If the macro exists, it is defined in the
&lt;<strong>unistd.h</strong>&gt; header file. This symbol affects the behavior
of such functions as <strong>setuid()</strong> and <strong>
setgid()</strong>.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_STREAM_MAX</em></td>
<td align="left" valign="top">Represents the STREAM_MAX macro, which indicates
the maximum number of streams that a job can have open at one time. The macro
is defined in the &lt;<strong>limits.h</strong>&gt; header file.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_TZNAME_MAX</em></td>
<td align="left" valign="top">(Not supported by the iSeries server). Represents
the TZNAME_MAX macro, which indicates the maximum length of the name of a time
zone. If the macro exists, it is defined in the
&lt;<strong>limits.h</strong>&gt; header file.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_VERSION</em></td>
<td align="left" valign="top">(Not supported by the iSeries server). Represents
the _POSIX_VERSION macro, which indicates the version of the POSIX.1 standard
that the system conforms to. If the macro exists, it is defined in the
&lt;<strong>unistd.h</strong>&gt; header file.<br>
<br>
</td>
</tr>
<tr>
<td align="left" valign="top"><em>_SC_CCSID</em></td>
<td align="left" valign="top">Represents the default coded character set
identifier (CCSID) used internally for integrated file system path names. A
CCSID uniquely identifies the coded graphic character representation of a path
name and includes such information as the character set and code page
identifier. The symbol _SC_CCSID is defined as the decimal value 10.</td>
</tr>
</table>
<br>
<br>
<h3>Authorities</h3>
<p>No authorization is required.</p>
<br>
<h3>Return Value</h3>
<table cellpadding="5">
<!-- cols="10 90" -->
<tr>
<td align="left" valign="top"><em>value</em></td>
<td align="left" valign="top"><strong>sysconf()</strong> was successful. The
value associated with the specified option is returned.</td>
</tr>
<tr>
<td align="left" valign="top"><em>-1</em></td>
<td align="left" valign="top">One of the following has occurred:
<ul>
<li>The variable corresponding to <strong>name</strong> is valid but is not
supported by the system. The <strong>errno</strong> global variable is not
changed.</li>
<li><strong>sysconf()</strong> failed in some other way. The <strong>
errno</strong> is set to indicate the error.</li>
</ul>
</td>
</tr>
</table>
<br>
<br>
<h3>Error Conditions</h3>
<p>If <strong>sysconf()</strong> is not successful, <strong>errno</strong>
usually indicates one of the following errors. Under some conditions, <strong>
errno</strong> could indicate an error other than those listed here.</p>
<table cellpadding="5">
<!-- cols="25 75" -->
<tr>
<th align="left" valign="bottom">Error condition</th>
<th align="left" valign="bottom">Additional information</th>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EBADFID">EBADFID</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td></tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EINVAL">EINVAL</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
</table>
<br>
<br>
<h3>Error Messages</h3>
<p>The following messages may be sent from this function:</p>
<table width="100%" cellpadding="5">
<!-- cols="15 85" -->
<tr>
<th align="left" valign="top">Message ID</th>
<th align="left" valign="top">Error Message Text</th>
</tr>
<tr>
<td align="left" valign="top">CPE3418 E</td>
<td align="left" valign="top">Possible APAR condition or hardware failure.</td>
</tr>
<tr>
<td align="left" valign="top">CPF3CF2 E</td>
<td align="left" valign="top">Error(s) occurred during running of &amp;1
API.</td>
</tr>
</table>
<br>
<br>
<h3>Related Information</h3>
<ul>
<li>The &lt;<strong>unistd.h</strong>&gt; file (see <a href="unix13.htm">Header
Files for UNIX-Type Functions</a>)</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 determines the value of OPEN_MAX:</p>
<pre>
#include &lt;stdio.h&gt;
#include &lt;unistd.h&gt;
#include &lt;errno.h&gt;
main() {
long result;
errno = 0;
puts("examining OPEN_MAX limit");
if ((result = sysconf(_SC_OPEN_MAX)) == -1)
if (errno == 0)
puts("OPEN_MAX is not supported.");
else perror("sysconf() error");
else
printf("OPEN_MAX is %ld\n", result);
}
</pre>
<br>
<p><strong>Output:</strong></p>
<pre>
examining OPEN_MAX limit
OPEN_MAX is 200
</pre>
<br>
<hr>
API introduced: V3R1
<hr>
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