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<title>Berkeley DB Reference Guide: Opening databases within the environment</title>
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<td><dl><dt>Berkeley DB Reference Guide:<dd>Environment</dl></td>
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Opening databases within the environment
Once the environment has been created, database handles may be created
and then opened within the environment. This is done by calling the
<a href="../../api_c/db_class.html">db_create</a> function and specifying the appropriate environment
as an argument.
File naming, database operations, and error handling will all be done as
specified for the environment. For example, if the <a href="../../api_c/env_open.html#DB_INIT_LOCK">DB_INIT_LOCK</a>
or <a href="../../api_c/env_open.html#DB_INIT_CDB">DB_INIT_CDB</a> flags were specified when the environment was
created or joined, database operations will automatically perform all
necessary locking operations for the application.
The following is a simple example of opening two databases within a
database environment:
<blockquote><pre>	DB_ENV *dbenv;
	DB *dbp1, *dbp2;
	int ret;

	dbenv = NULL;
	dbp1 = dbp2 = NULL;

	/*
	 * Create an environment and initialize it for additional error
	 * reporting.
	 */
	if ((ret = db_env_create(&dbenv, 0)) != 0) {
		fprintf(errfp, "%s: %s\n", progname, db_strerror(ret));
		return (ret);
	}

	dbenv-&gt;set_errfile(dbenv, errfp);
	dbenv-&gt;set_errpfx(dbenv, progname);

	/* Open an environment with just a memory pool. */
	if ((ret =
	 dbenv-&gt;open(dbenv, home, DB_CREATE | DB_INIT_MPOOL, 0)) != 0) {
		dbenv-&gt;err(dbenv, ret, "environment open: %s", home);
		goto err;
	}

	/* Open database #1. */
	if ((ret = db_create(&dbp1, dbenv, 0)) != 0) {
		dbenv-&gt;err(dbenv, ret, "database create");
		goto err;
	}
	if ((ret = dbp1-&gt;open(dbp1,
	 NULL, DATABASE1, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
		dbenv-&gt;err(dbenv, ret, "DB-&gt;open: %s", DATABASE1);
		goto err;
	}

	/* Open database #2. */
	if ((ret = db_create(&dbp2, dbenv, 0)) != 0) {
		dbenv-&gt;err(dbenv, ret, "database create");
		goto err;
	}
	if ((ret = dbp2-&gt;open(dbp2,
	 NULL, DATABASE2, NULL, DB_HASH, DB_CREATE, 0664)) != 0) {
		dbenv-&gt;err(dbenv, ret, "DB-&gt;open: %s", DATABASE2);
		goto err;
	}

	return (0);

err:	if (dbp2 != NULL)
		(void)dbp2-&gt;close(dbp2, 0);
	if (dbp1 != NULL)
		(void)dbp2-&gt;close(dbp1, 0);
	(void)dbenv-&gt;close(dbenv, 0);
	return (1);
}</pre></blockquote>
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