mirror of
https://github.com/yasuhirokimura/db18
synced 2026-06-08 18:29:23 +00:00
Yasuhiro KIMURA
124 lines
5.0 KiB
HTML
124 lines
5.0 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Error support</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="up" href="env.html" title="Chapter 9. The Berkeley DB Environment" />
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<link rel="prev" href="env_open.html" title="Opening databases within the environment" />
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<link rel="next" href="env_db_config.html" title="DB_CONFIG configuration file" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 18.1.40</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Error support</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="env_open.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 9. The Berkeley DB Environment </th>
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<td width="20%" align="right"> <a accesskey="n" href="env_db_config.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="env_error"></a>Error support</h2>
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</div>
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</div>
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</div>
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<p>
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Berkeley DB offers programmatic support for displaying error
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return values. The <a href="../api_reference/C/envstrerror.html" class="olink">db_strerror()</a> function returns a pointer to
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the error message corresponding to any Berkeley DB error
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return. This is similar to the ANSI C strerror interface, but
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can handle both system error returns and Berkeley DB-specific
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return values.
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</p>
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<p>
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For example:
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</p>
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<a id="prog_env29"></a>
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<pre class="programlisting">int ret;
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if ((ret = dbenv->set_cachesize(dbenv, 0, 32 * 1024, 1)) != 0) {
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fprintf(stderr, "set_cachesize failed: %s\n", db_strerror(ret));
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return (1);
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}
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</pre>
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<p>
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There are also two additional error methods: <a href="../api_reference/C/enverr.html" class="olink">DB_ENV->err()</a> and
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<code class="methodname">DB_ENV->errx()</code>. These methods
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work like the ANSI C printf function, taking a printf-style
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format string and argument list, and writing a message
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constructed from the format string and arguments.
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</p>
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<p>
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The <a href="../api_reference/C/enverr.html" class="olink">DB_ENV->err()</a> function appends the standard error string to
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the constructed message; the
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<code class="methodname">DB_ENV->errx()</code> function does
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not.
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</p>
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<p>
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Error messages can be configured always to include a prefix
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(for example, the program name) using the <a href="../api_reference/C/envset_errpfx.html" class="olink">DB_ENV->set_errpfx()</a>
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method.
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</p>
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<p>
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These functions provide simpler ways of displaying Berkeley
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DB error messages:
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</p>
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<a id="prog_env30"></a>
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<pre class="programlisting">int ret;
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...
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dbenv->set_errpfx(dbenv, program_name);
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if ((ret = dbenv->open(dbenv, home,
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DB_CREATE | DB_INIT_LOG | DB_INIT_TXN | DB_USE_ENVIRON, 0))
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!= 0) {
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dbenv->err(dbenv, ret, "open: %s", home);
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dbenv->errx(dbenv,
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"contact your system administrator: session ID was %d",
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session_id);
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return (1);
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}</pre>
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<p>
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For example, if the program was called "my_app", and it
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tried to open an environment home directory in "/tmp/home" and
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the open call returned a permission error, the error messages
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shown would look like this:
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</p>
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<pre class="programlisting">my_app: open: /tmp/home: Permission denied.
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my_app: contact your system administrator: session ID was 2</pre>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="env_open.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="env.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="env_db_config.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Opening databases within the
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environment </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> DB_CONFIG configuration
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file</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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