<!--$Id: error.so,v 10.22 2003/10/18 19:15:56 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB Reference Guide: Error support</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <a name="2"><!--meow--></a> <table width="100%"><tr valign=top> <td><b><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></b></td> <td align=right><a href="../am_misc/perm.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../am_misc/stability.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p align=center><b>Error support</b></p> <p>Berkeley DB offers programmatic support for displaying error return values.</p> <p>The <a href="../../api_c/env_strerror.html">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> <blockquote><pre>int ret; if ((ret = dbp->put(dbp, NULL, &key, &data, 0)) != 0) { fprintf(stderr, "put failed: %s\n", db_strerror(ret)); return (1); }</pre></blockquote> <p>There are also two additional error methods, <a href="../../api_c/db_err.html">DB->err</a> and <a href="../../api_c/db_err.html">DB->errx</a>. 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_c/db_err.html">DB->err</a> method appends the standard error string to the constructed message; the <a href="../../api_c/db_err.html">DB->errx</a> 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_c/db_set_errpfx.html">DB->set_errpfx</a> method.</p> <blockquote><pre>#define DATABASE "access.db" <p> int ret; <p> (void)dbp->set_errpfx(dbp, program_name); <p> 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></blockquote> <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> <blockquote><pre>my_app: access.db: Permission denied. my_app: contact your system administrator: session ID was 14</pre></blockquote> <table width="100%"><tr><td><br></td><td align=right><a href="../am_misc/perm.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../am_misc/stability.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>