138 lines
6.3 KiB
HTML
138 lines
6.3 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Example: Using environment variables" />
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<meta name="abstract" content="This program displays the value of an environment variable and then sets the environment variable to a new value." />
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<meta name="description" content="This program displays the value of an environment variable and then sets the environment variable to a new value." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Example: Using environment variables</title>
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</head>
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<body id="apiexusvar"><a name="apiexusvar"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Example: Using environment variables</h1>
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<div><p>This program displays the value of an environment variable and
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then sets the environment variable to a new value.</p>
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<div class="section"><p>Use the Create C Module (CRTCMOD) and the Create Program (CRTPGM)
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commands to create this program.</p>
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<p>Call this program with one parameter
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to display the environment variable specified by that parameter. Call this
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program with two parameters to set the environment variable specified by the
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first parameter to the value specified by the second parameter.</p>
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<div class="note"><span class="notetitle">Note:</span> Read
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the <a href="codedisclaimer.htm">Code license and disclaimer information</a> for important legal information.</div>
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<pre>/******************************************************************/
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/******************************************************************/
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/* */
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/* FUNCTION: Display the value of an environment variable and */
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/* then set the environment variable to a new value. */
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/* */
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/* LANGUAGE: ILE C */
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/* */
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/* APIs USED: getenv(), putenv() */
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/* */
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/******************************************************************/
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/******************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <string.h>
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#define BUFLEN 1024
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int main(int argc, char *argv[])
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{
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int num=0; /* counter */
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int rc; /* API return code */
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int l1, l2; /* lengths of the two parameters */
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char *envvar=NULL; /* pointer to an environment variable*/
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char **envvaridx=NULL; /* pointer to an envvar pointer */
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char envstring[BUFLEN];
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/* buffer to construct putenv request*/
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/* Show a small usage message. */
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if ((argc != 2) && (argc != 3)) {
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printf("Usage: %s <ENV_VAR> <new_value>\n OR \n"
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"Usage: %s <ENV_VAR>\n", argv[0], argv[0]);
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printf("Sets an environment variable to a user requested\n"
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"value\n"
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"OR\nDisplays the value of a single environment variable\n");
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exit(1);
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}
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if (argc == 2) {
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/* Called just to display the environment variables. */
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envvar = getenv(argv[1]);
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if (envvar == NULL) {
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printf("No environment variable %s set\n",
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argv[1]);
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}
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else {
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printf("Environment variable: %s\n", envvar);
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}
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return 0;
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}
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/* ELSE, called to set an environment variable. */
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/* Check the size of the parameters and construct a string of */
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/* the form "VAR=string" which is valid input to putenv. */
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l1 = strlen(argv[1]);
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l2 = strlen(argv[2]);
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if (l1+l2+2 >= BUFLEN) {
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printf("Only 1024 characters total allowed for this test\n");
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exit(1);
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}
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memcpy(envstring, argv[1], l1);
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envstring[l1] = '=';
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memcpy(&envstring[l1+1], argv[2], l2);
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envstring[l1+l2+1]='\0';
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/* Now that the string is built, let's see if the environment */
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/* variable was already set. */
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envvar = getenv(argv[1]);
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if (envvar == NULL) {
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printf("Setting NEW environment variable %s\n",
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envstring);
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}
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else {
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printf("Resetting OLD environment variable from: %s\n to %s\n",
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envvar, envstring);
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}
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/* Now actually set the environment variable. */
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rc = putenv(envstring);
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if (rc < 0) {
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printf("putenv failed, errno = %d\n", errno);
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return -1;
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}
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printf("Environment variable set\n");
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return 0;
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}</pre>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="apiexmp.htm" title="Contains example programs that use APIs and exit programs.">Examples: APIs</a></div>
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</div>
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</div>
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</body>
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