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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<p>Library Version 11.2.5.3</p>
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="dbErrorReporting"></a>Error Reporting Functions</h2>
</div>
</div>
</div>
<p>
To simplify error reporting and handling, the
<span><code class="classname">DB</code> structure</span>
offers several useful methods.
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="methodname">set_errcall()</code>
</p>
<p>
Defines the function that is called when an error message is
issued by DB. The error prefix and message are passed to
this callback. It is up to the application to display this
information correctly.
</p>
</li>
<li>
<p>
<code class="methodname">set_errfile()</code>
</p>
<p>
Sets the C library <code class="literal">FILE *</code> to be used for
displaying error messages issued by the DB library.
</p>
</li>
<li>
<p>
<code class="methodname">set_errpfx()</code>
</p>
<p>
Sets the prefix used for any error messages issued by the
DB library.
</p>
</li>
<li>
<p>
<code class="methodname">err()</code>
</p>
<p>
Issues an error message. The error message is sent to the
callback function as defined by <code class="methodname">set_errcall</code>.
If that method has not been used, then the error message is sent to the
file defined by
<span><code class="methodname">set_errfile()</code>.</span>
If none of these methods have been used, then the error message is sent to
standard error.
</p>
<p>
The error message consists of the prefix string
(as defined by <code class="methodname">set_errpfx()</code>),
an optional <code class="literal">printf</code>-style formatted message,
the error message, and a trailing newline.
</p>
</li>
<li>
<p>
<code class="methodname">errx()</code>
</p>
<p>
Behaves identically to <code class="methodname">err()</code> except
that the DB message text associated with the supplied error
value is not appended to the error string.
</p>
</li>
</ul>
</div>
<p>
In addition, you can use the <code class="methodname">db_strerror()</code>
function to directly return the error string that corresponds to a
particular error number.
</p>
<p>
For example, to send all error messages for a given database handle
to a callback for handling, first create your callback. Do something like this:
</p>
<a id="c_db8"></a>
<pre class="programlisting">/*
* Function called to handle any database error messages
* issued by DB.
*/
void
my_error_handler(const DB_ENV *dbenv, const char *error_prefix,
const char *msg)
{
/*
* Put your code to handle the error prefix and error
* message here. Note that one or both of these parameters
* may be NULL depending on how the error message is issued
* and how the DB handle is configured.
*/
} </pre>
<p>
And then register the callback as follows:
</p>
<a id="c_db9"></a>
<pre class="programlisting">#include <db.h>
#include <stdio.h>
...
DB *dbp;
int ret;
/*
* Create a database and initialize it for error
* reporting.
*/
ret = db_create(&dbp, NULL, 0);
if (ret != 0) {
fprintf(stderr, "%s: %s\n", "my_program",
db_strerror(ret));
return(ret);
}
/* Set up error handling for this database */
dbp->set_errcall(dbp, my_error_handler);
dbp->set_errpfx(dbp, "my_example_program"); </pre>
<p>
And to issue an error message:
</p>
<a id="c_db10"></a>
<pre class="programlisting">ret = dbp->open(dbp,
NULL,
"mydb.db",
NULL,
DB_BTREE,
DB_CREATE,
0);
if (ret != 0) {
dbp->err(dbp, ret,
"Database open failed: %s", "mydb.db");
return(ret);
}</pre>
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