mirror of
https://github.com/yasuhirokimura/db18
synced 2026-06-08 18:29:23 +00:00
Yasuhiro KIMURA
133 lines
5.5 KiB
HTML
133 lines
5.5 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||
<html xmlns="http://www.w3.org/1999/xhtml">
|
||
<head>
|
||
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
||
<title>Error support</title>
|
||
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
||
<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
|
||
<link rel="up" href="am_misc.html" title="Chapter 4. Access Method Wrapup" />
|
||
<link rel="prev" href="am_misc_perm.html" title="Retrieved key/data permanence for C/C++" />
|
||
<link rel="next" href="am_misc_stability.html" title="Cursor stability" />
|
||
</head>
|
||
<body>
|
||
<div xmlns="" class="navheader">
|
||
<div class="libver">
|
||
<p>Library Version 18.1.40</p>
|
||
</div>
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">Error support</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="am_misc_perm.html">Prev</a> </td>
|
||
<th width="60%" align="center">Chapter 4. Access Method Wrapup </th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="am_misc_stability.html">Next</a></td>
|
||
</tr>
|
||
</table>
|
||
<hr />
|
||
</div>
|
||
<div class="sect1" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title" style="clear: both"><a id="am_misc_error"></a>Error support</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
Berkeley DB offers programmatic support for displaying error
|
||
return values.
|
||
</p>
|
||
<p>
|
||
The <a href="../api_reference/C/envstrerror.html" class="olink">db_strerror()</a> function returns a pointer to the error
|
||
message corresponding to any Berkeley DB error return, similar
|
||
to the ANSI C strerror function, but is able to handle both
|
||
system error returns and Berkeley DB specific return
|
||
values.
|
||
</p>
|
||
<p>
|
||
For example:
|
||
</p>
|
||
<a id="prog_am25"></a>
|
||
<pre class="programlisting">int ret;
|
||
...
|
||
if ((ret = dbp->put(dbp, NULL, &key, &data, 0)) != 0) {
|
||
fprintf(stderr, "put failed: %s\n", db_strerror(ret));
|
||
return (1);
|
||
}</pre>
|
||
<p>
|
||
There are also two additional error methods, <a href="../api_reference/C/dberr.html" class="olink">DB->err()</a> and
|
||
<code class="methodname">DB->errx()</code>. These methods work
|
||
like the ANSI C X3.159-1989 (ANSI C) printf function, taking a
|
||
printf-style format string and argument list, and writing a
|
||
message constructed from the format string and
|
||
arguments.
|
||
</p>
|
||
<p>
|
||
The <a href="../api_reference/C/dberr.html" class="olink">DB->err()</a> method appends the standard error string to the
|
||
constructed message; the
|
||
<code class="methodname">DB->errx()</code> method does not.
|
||
These methods provide simpler ways of displaying Berkeley DB
|
||
error messages. For example, if your application tracks
|
||
session IDs in a variable called session_id, it can include
|
||
that information in its error messages:
|
||
</p>
|
||
<p>
|
||
Error messages can additionally be configured to always
|
||
include a prefix (for example, the program name) using the
|
||
<a href="../api_reference/C/dbset_errpfx.html" class="olink">DB->set_errpfx()</a> method.
|
||
</p>
|
||
<a id="prog_am26"></a>
|
||
<pre class="programlisting">#define DATABASE "access.db"
|
||
|
||
int ret;
|
||
|
||
(void)dbp->set_errpfx(dbp, program_name);
|
||
|
||
if ((ret = dbp->open(dbp,
|
||
NULL, DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
|
||
dbp->err(dbp, ret, "%s", DATABASE);
|
||
dbp->errx(dbp,
|
||
"contact your system administrator: session ID was %d",
|
||
session_id);
|
||
return (1);
|
||
}</pre>
|
||
<p>
|
||
For example, if the program were called my_app and the open
|
||
call returned an EACCESS system error, the error messages
|
||
shown would appear as follows:
|
||
</p>
|
||
<pre class="programlisting">my_app: access.db: Permission denied.
|
||
my_app: contact your system administrator: session ID was 14</pre>
|
||
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
|
||
<h3 class="title">Note</h3>
|
||
<p>
|
||
Equivalent methods exist for informational messages. See
|
||
<a href="../api_reference/C/dbmsg.html" class="olink">DB->msg()</a> and <a href="../api_reference/C/dbset_msgpfx.html" class="olink">DB->set_msgpfx()</a> for details.
|
||
</p>
|
||
</div>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="am_misc_perm.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="am_misc.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="am_misc_stability.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Retrieved key/data permanence for C/C++ </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Cursor stability</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|