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<th colspan="3" align="center">Opening databases within the environment</th>
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<h2 class="title" style="clear: both"><a id="env_open"></a>Opening databases within the environment</h2>
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<p>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_reference/C/dbcreate.html" class="olink">db_create()</a> function and specifying the appropriate environment
as an argument.</p>
<p>File naming, database operations, and error handling will all be done as
specified for the environment. For example, if the <a href="../api_reference/C/envopen.html#envopen_DB_INIT_LOCK" class="olink">DB_INIT_LOCK</a>
or <a href="../api_reference/C/envopen.html#envopen_DB_INIT_CDB" class="olink">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.</p>
<p>The following is a simple example of opening two databases within a
database environment:</p>
<a id="prog_env28"></a>
<pre class="programlisting">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->set_errfile(dbenv, errfp);
dbenv->set_errpfx(dbenv, progname);
/* Open an environment with just a memory pool. */
if ((ret =
dbenv->open(dbenv, home, DB_CREATE | DB_INIT_MPOOL, 0)) != 0) {
dbenv->err(dbenv, ret, "environment open: %s", home);
goto err;
}
/* Open database #1. */
if ((ret = db_create(&dbp1, dbenv, 0)) != 0) {
dbenv->err(dbenv, ret, "database create");
goto err;
}
if ((ret = dbp1->open(dbp1,
NULL, DATABASE1, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
dbenv->err(dbenv, ret, "DB->open: %s", DATABASE1);
goto err;
}
/* Open database #2. */
if ((ret = db_create(&dbp2, dbenv, 0)) != 0) {
dbenv->err(dbenv, ret, "database create");
goto err;
}
if ((ret = dbp2->open(dbp2,
NULL, DATABASE2, NULL, DB_HASH, DB_CREATE, 0664)) != 0) {
dbenv->err(dbenv, ret, "DB->open: %s", DATABASE2);
goto err;
}
return (0);
err: if (dbp2 != NULL)
(void)dbp2->close(dbp2, 0);
if (dbp1 != NULL)
(void)dbp1->close(dbp1, 0);
(void)dbenv->close(dbenv, 0);
return (1);
}</pre>
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