300 lines
8.4 KiB
HTML
300 lines
8.4 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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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>putenv()--Change or Add Environment Variable</title>
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<!-- Begin Header Records ========================================== -->
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Change History: -->
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<!-- Direct1 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 -->
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<!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 -->
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<!-- This file has undergone html cleanup on 04/29/02 by JET -->
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<!-- End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>putenv()--Change or Add Environment Variable</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 <stdlib.h>
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int putenv(const char <em>*string</em>);;
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</pre>
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Service Program Name: QP0ZCPA<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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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes. See Usage Notes for more information.<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>putenv()</strong> function sets the value of a job-level
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environment variable by changing an existing variable or creating a new one.
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The <em>string</em> parameter points to a string of the form <samp>
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name=value</samp>, where <samp>name</samp> is the environment variable and
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<samp>value</samp> is the new value for it.</p>
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<p>The <samp>name</samp> cannot contain a blank. For example,</p>
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<pre>
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PATH NAME=/my_lib/joe_user
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</pre>
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<p>is not valid because of the blank between <samp>PATH</samp> and <samp>
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NAME</samp>. The name can contain an equal (=) symbol, but the system
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interprets all characters following the first equal symbol as being the value
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of the environment variable. For example,</p>
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<pre>
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PATH=NAME=/my_lib/joe_user
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</pre>
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<p>will result in a value of 'NAME=/my_lib/joe_user' for the variable PATH.</p>
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<br>
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<!-- Please NOTE: DO NOT DELETE THIS SECTION if this API has no authorities and locks. -->
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<!-- Instead, use the commented out coding below to indicate NONE. -->
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<h3>Authorities and Locks</h3>
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<!-- Use this if there are no authorities and locks. -->
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<p>None.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong><em>string</em></strong></dt>
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<dd>(Input) A pointer to the <samp>name=value</samp> string.</dd>
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</dl>
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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>putenv()</strong> was 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>putenv()</strong> was not successful. The
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<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>Error Conditions</h3>
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<p>If <strong>putenv()</strong> is not successful, <em>errno</em> indicates one
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of the following errors.</p>
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<dl compact>
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<dt><em>[EDAMAGE]</em></dt>
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<dd>
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<p>A damaged object was encountered.</p>
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<p>A referenced object is damaged. The object cannot be used.</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. In attempting to use an
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argument in a call, the system detected an address 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>[EINVAL]</em></dt>
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<dd>
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<p>The value specified for the argument is not correct. A function was passed
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incorrect argument values, or an operation was attempted on an object and the
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operation specified is not supported for that type of object.</p>
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<p>An argument value is not valid, out of range, or NULL. For example, the
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string may not be in the correct format.</p>
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</dd>
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<dt><em>[ENOMEM]</em></dt>
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<dd>
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<p>Storage allocation request failed.</p>
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<p>A function needed to allocate storage, but no storage is available.</p>
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<p>There is not enough memory to perform the requested function. (There is a
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limit of 4095 environment variables per job.)</p>
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</dd>
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<dt><em>[EUNKNOWN]</em></dt>
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<dd>
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<p>Unknown system state.</p>
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<p>The operation failed because of an unknown system state. See any messages in
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the job log and correct any errors that are indicated, then retry the
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operation.</p>
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</dd>
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</dl>
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<br>
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<h3>Usage Notes</h3>
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<ol>
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<li>Although <strong>putenv()</strong> is threadsafe, if a thread calls an
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environment variable function while another thread is accessing an environment
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variable from the environ array the thread may see undefined results. The
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environ array can be accessed directly or by using a pointer returned from the
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<strong>getenv()</strong> or <strong>Qp0zGetEnv()</strong> functions. The
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environment contents are only protected during calls to the environment
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variable functions.<br>
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</li>
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<li>All environment variables are stored with an associated CCSID (coded
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character set identifier). Because <strong>putenv()</strong> does not specify a
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CCSID, the default CCSID for the job is used as the CCSID associated with
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strings that are stored using <strong>putenv()</strong>.<br>
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</li>
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<li>No translation is done based on the CCSID. The CCSID is just stored and
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retrieved as an integer value associated with each environment variable.</li>
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</ol>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li><a href="evgetenv.htm">getenv()</a>--Get Value of Environment Variable</li>
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<li><a href="evdltenv.htm">Qp0zDltEnv()</a>--Delete an Environment
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Variable</li>
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<li><a href="evdltsev.htm">Qp0zDltSysEnv()</a>--Delete a System-Level
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Environment Variable</li>
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<li><a href="evgetall.htm">Qp0zGetAllSysEnv()</a>--Get All System-Level
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Environment Variables</li>
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<li><a href="evgenvxt.htm">Qp0zGetEnv()</a>--Get Value of Environment Variable
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(Extended)</li>
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<li><a href="evgetsev.htm">Qp0zGetSysEnv()</a>--Get Value of System-Level
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Environment Variable</li>
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<li><a href="evinenv.htm">Qp0zInitEnv()</a>--Initialize Environment for
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Variables</li>
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<li><a href="evpenvxt.htm">Qp0zPutEnv()</a>--Change or Add Environment Variable
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(Extended)</li>
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<li><a href="evputsev.htm">Qp0zPutSysEnv()</a>--Change or Add a System-Level
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Environment</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 uses <strong>putenv()</strong> and <strong>
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getenv()</strong>.</p>
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<pre>
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#include <stdio.h>
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#include <errno.h>
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#include <stdlib.h>
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int main(int argc, char **argv)
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{
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char *var1 = "PATH=/:/home/userid";
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char *name1 = "PATH";
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char *val1 = NULL;
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int rc;
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rc = putenv(var1);
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if (rc < 0) {
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printf("Error inserting <%s> in environ, errno = %d\n",
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var1, errno);
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return 1;
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}
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printf("<%s> inserted in environ\n", var1);
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val1 = getenv(name1);
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if (val1 == NULL) {
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printf("Error retrieving <%s> from environ, errno = %d\n",
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name1, errno);
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return 1;
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}
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printf("<%s> retrieved from environ, value is <%s>\n",
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name1, val1);
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return 0;
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}
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</pre>
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<p><strong>Output:</strong></p>
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<pre>
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<PATH=/:/home/userid> inserted in environ
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<PATH> retrieved from environ, value is </:/home/userid>
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</pre>
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<p>For other examples, see the following:</p>
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<ul>
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<li><a href="../apiref/apiexusvar.htm">Using Environment Variables</a>.<br>
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</li>
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<li><a href="../apiref/apiexuspro.htm">Using the Spawn Process and Wait for Child
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Process APIs</a>.<br>
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</li>
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<li><a href="spawnu.htm#spawnuexmp">Using the Spawn Process (using NLS-enabled
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path name)</a></li>
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</ul>
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<br>
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<hr>
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API introduced: V3R6
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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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