<!--$Id: errors.so,v 10.20 2001/03/01 15:58:13 bostic Exp $--> <!--Copyright 1997-2002 by Sleepycat Software, Inc.--> <!--All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB Reference Guide: Error returns</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Simple Tutorial</dl></h3></td> <td align=right><a href="../../ref/simple_tut/handles.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/simple_tut/open.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p> <h1 align=center>Error returns</h1> <p>The Berkeley 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>If a system error occurred (for example, Berkeley 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), Berkeley DB returns an <b>errno</b> value. All of the possible values of <b>errno</b> are greater than 0. <p>If the operation didn't fail due to a system error, but wasn't successful either, Berkeley DB returns a special error value. For example, if you tried to retrieve the data item associated with the key <b>fruit</b>, and there was no such key/data pair in the database, Berkeley DB would return <a href="../../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a>, 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>Berkeley DB also offers programmatic support for displaying error return values. First, the <a href="../../api_c/env_strerror.html">db_strerror</a> interface returns a pointer to the error message corresponding to any Berkeley DB error return, similar to the ANSI C strerror interface, but is able to handle both system error returns and Berkeley DB-specific return values. <p>Second, there are two error functions, <a href="../../api_c/db_err.html">DB->err</a> and <a href="../../api_c/db_err.html">DB->errx</a>. These functions work like the ANSI C printf interface, 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. <table width="100%"><tr><td><br></td><td align=right><a href="../../ref/simple_tut/handles.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/simple_tut/open.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> </body> </html>
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