102 lines
4.4 KiB
HTML
102 lines
4.4 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 Returns</title>
|
||
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.62.4" />
|
||
<link rel="home" href="index.html" title="Getting Started with Berkeley DB" />
|
||
<link rel="up" href="introduction.html" title="Chapter 1. Introduction to Berkeley DB " />
|
||
<link rel="previous" href="environments.html" title="Environments" />
|
||
<link rel="next" href="gettingit.html" title="Getting and Using DB " />
|
||
</head>
|
||
<body>
|
||
<div class="navheader">
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">Error Returns</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="environments.html">Prev</a> </td>
|
||
<th width="60%" align="center">Chapter 1. Introduction to Berkeley DB </th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="gettingit.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="returns"></a>Error Returns</h2>
|
||
</div>
|
||
</div>
|
||
<div></div>
|
||
</div>
|
||
<p>
|
||
Before continuing, it is useful to spend a few moments on error returns
|
||
in DB.
|
||
</p>
|
||
<p>
|
||
|
||
<span>The</span>
|
||
DB interfaces always return a value of 0 on success. If the
|
||
operation does not succeed for any reason, the return value will be
|
||
non-zero.
|
||
</p>
|
||
<p>
|
||
If a system error occurred (for example, DB ran out of disk
|
||
space, or permission to access a file was denied, or an illegal argument
|
||
was specified to one of the interfaces), DB returns an
|
||
<tt class="literal">errno</tt>
|
||
value. All of the possible values of <tt class="literal">errno</tt> are greater than 0.
|
||
</p>
|
||
<p>
|
||
If the operation did not fail due to a system error, but was not
|
||
successful either, DB returns a special error value. For
|
||
example, if you tried to retrieve data from the database and the
|
||
record for which you are searching does not exist, DB would return
|
||
<tt class="literal">DB_NOTFOUND</tt>, a special error value that means the requested
|
||
key does not appear in the database. All of the possible special error
|
||
values are less than 0.
|
||
</p>
|
||
<p>
|
||
DB also offers programmatic support for displaying error return
|
||
values. First, the <tt class="function">db_strerror</tt> function returns
|
||
a pointer to the error
|
||
message corresponding to any DB error return, similar to the
|
||
ANSI C <tt class="function">strerror</tt> function, but is able to handle
|
||
both system error returns and DB-specific return values.
|
||
</p>
|
||
<p>
|
||
Second, there are two error functions,
|
||
<tt class="methodname">DB->err</tt> and <tt class="methodname">DB->errx</tt>.
|
||
These functions work like the ANSI C <tt class="function">printf</tt> function,
|
||
taking a printf-style format string and argument list, and optionally
|
||
appending the standard error string to a message constructed from
|
||
the format string and other arguments.
|
||
</p>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="environments.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="introduction.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="gettingit.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Environments </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Getting and Using DB </td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|