1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
|
<!--$Id: error.so,v 10.14 2000/12/18 21:05:13 bostic Exp $-->
<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
<!--All rights reserved.-->
<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,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
</head>
<body bgcolor=white>
<a name="2"><!--meow--></a>
<table><tr valign=top>
<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></h3></td>
<td width="1%"><a href="../../ref/am/verify.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/arch/bigpic.html"><img src="../../images/next.gif" alt="Next"></a>
</td></tr></table>
<p>
<h1 align=center>Error support</h1>
<p>Berkeley DB offers programmatic support for displaying error return values.
<p>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>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 interfaces, <a href="../../api_c/db_err.html">DB->err</a> and
<a href="../../api_c/db_err.html">DB->errx</a>. These interfaces work like the ANSI C X3.159-1989 (ANSI C) printf
interface, taking a printf-style format string and argument list, and
writing a message constructed from the format string and arguments.
<p>The <a href="../../api_c/db_err.html">DB->err</a> function appends the standard error string to the constructed
message, the <a href="../../api_c/db_err.html">DB->errx</a> function does not. These interfaces 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>Error messages can additionally be configured to always include a prefix
(e.g., the program name) using the <a href="../../api_c/db_set_errpfx.html">DB->set_errpfx</a> interface.
<p><blockquote><pre>#define DATABASE "access.db"
int ret;
dbp->errpfx(dbp, argv0);
if ((ret =
dbp->open(dbp, DATABASE, 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 was 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><tr><td><br></td><td width="1%"><a href="../../ref/am/verify.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/arch/bigpic.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>
|
