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<h2 class="title" style="clear: both"><a id="am_misc_error"></a>Error support</h2>
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<p>Berkeley DB offers programmatic support for displaying error return values.</p>
<p>The <a href="../api_reference/C/envstrerror.html" class="olink">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>
<a id="prog_am25"></a>
<pre class="programlisting">int ret;
...
if ((ret = dbp->put(dbp, NULL, &key, &data, 0)) != 0) {
fprintf(stderr, "put failed: %s\n", db_strerror(ret));
return (1);
}</pre>
<p>There are also two additional error methods, <a href="../api_reference/C/dberr.html" class="olink">DB->err()</a> and
<code class="methodname">DB->errx()</code>. 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_reference/C/dberr.html" class="olink">DB->err()</a> method appends the standard error string to the
constructed message; the <code class="methodname">DB->errx()</code> 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_reference/C/dbset_errpfx.html" class="olink">DB->set_errpfx()</a> method.</p>
<a id="prog_am26"></a>
<pre class="programlisting">#define DATABASE "access.db"
int ret;
(void)dbp->set_errpfx(dbp, program_name);
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>
<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>
<pre class="programlisting">my_app: access.db: Permission denied.
my_app: contact your system administrator: session ID was 14</pre>
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