102 lines
6.2 KiB
HTML
102 lines
6.2 KiB
HTML
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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>Environment Variable APIs</title>
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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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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<a name="Top_Of_Page"></a>
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<h2>Environment Variable APIs</h2>
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<p><strong>Environment variables</strong> are character strings of the form
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"name=value". There are two types of environment variables:</p>
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<ul>
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<li>Job-level environment variables. The job-level environment variables are
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stored in an environment space outside of the program associated with the job.
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They can be manipulated by using the <strong>getenv()</strong>, <strong>
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putenv()</strong>, <strong>Qp0zDltEnv()</strong>, <strong>
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Qp0zGetEnv()</strong>, <strong>Qp0zInitEnv()</strong>, and <strong>
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Qp0zPutEnv()</strong> APIs, as well as the CL commands ADDENVVAR, CHGENVVAR,
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RMVENVVAR, and WRKENVVAR. These variables exist for the duration of the job or
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until they are deleted. There is a limit of 4095 job-level environment
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variables.<br>
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<br>
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</li>
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<li>System-level environment variables. The system-level environment variables
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are stored in a global environment space that is persistent across IPLs and is
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not associated to a particular job. They can be manipulated by using the
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<strong>Qp0zDltSysEnv()</strong>, <strong>Qp0zGetAllSysEnv()</strong>, <strong>
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Qp0zGetSysEnv()</strong>, and <strong>Qp0zPutSysEnv()</strong> APIs, as well as
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the CL commands ADDENVVAR, CHGENVVAR, RMVENVVAR, and WRKENVVAR. These variables
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exist until they are deleted. There is a limit of 4095 system-level environment
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variables.</li>
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</ul>
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<p>When a job calls one of the job-level environment variable APIs or CL
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commands for the first time, it inherits the system-level environment variables
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onto its job-level environment space. Any changes to job-level and system-level
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environment variables are then independent of one another.</p>
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<p>The temporary space where the job-level environment variables are stored
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allows read and write access. Therefore, it is possible for the space to be
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corrupted. This could occur if a programmer accesses the space directly using
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the <samp>environ</samp> array rather than using the environment variable APIs.
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If the space is corrupted, subsequent calls using the APIs will have
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unpredictable results.</p>
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<p>The environment variable APIs are:</p>
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<!-- ***** NOTE ***** Do not manually update text or links in this section. -->
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<!-- Updates made in this section *will* be overlaid by automated tools -->
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<!-- Notify User Technologies of needed updates to be made in XML for API finder.-->
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<!--***************API BEGIN PASTE***************-->
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<ul>
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<li><A HREF="evgetenv.htm">getenv()</A> (Get value of environment variable) searches the job-level environment list for a string of the form name=value, where name is the environment variable and value is the value of the variable.</li>
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<li><A HREF="evputenv.htm">putenv()</A> (Change or add environment variable) sets the value of a job-level environment variable by changing an existing variable or creating a new one.</li>
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<li><A HREF="evdltenv.htm">Qp0zDltEnv()</A> (Delete an environment variable) deletes a single job-level environment variable or deletes all environment variables from the current job.</li>
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<li><A HREF="evdltsev.htm">Qp0zDltSysEnv()</A> (Delete a system-level environment variable) deletes a single system-level environment variable or deletes all system-level environment variables.</li>
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<li><A HREF="evgetall.htm">Qp0zGetAllSysEnv()</A> (Get all system-level environment variables) fills in the list_buf with a list of all the system-level environment variables.</li>
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<li><A HREF="evgenvxt.htm">Qp0zGetEnv()</A> (Get value of environment variable (extended)) is an i5/OS extension to the standard getenv() function.</li>
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<li><A HREF="evgetsev.htm">Qp0zGetSysEnv()</A> (Get value of system-level environment variable) gets the value of a system-level environment variable name by searching the system-level environment variable list for a string of the form name=value.</li>
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<li><A HREF="evinenv.htm">Qp0zInitEnv()</A> (Initialize environment for variables) sets the external variable environ to a pointer to the current environment list.</li>
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<li><A HREF="evpenvxt.htm">Qp0zPutEnv()</A> (Change or add environment variable (extended)) is an i5/OS extension to the standard putenv() function.</li>
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<li><A HREF="evputsev.htm">Qp0zPutSysEnv()</A> (Change or add a system-level environment variable) sets the value of a system-level environment variable by altering an existing variable or creating a new variable.</li>
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</ul>
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<!--***************API END PASTE***************-->
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<p><strong>Note:</strong> These functions use header (include) files from the
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library QSYSINC, which is optionally installable. Make sure QSYSINC is
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installed on your system before using any of the functions. See <a href=
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"unix13.htm">Header Files for UNIX-Type Functions</a> for the file and member
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name of each header file.</p>
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<hr>
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<table cellpadding="2" cellspacing="2" align="center">
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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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</body>
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</html>
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