Sindbad~EG File Manager
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<p>Library Version 18.1.40</p>
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<h2 class="title" style="clear: both"><a id="env_error"></a>Error support</h2>
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<p>
Berkeley DB offers programmatic support for displaying error
return values. 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. This is similar to the ANSI C strerror interface, but
can handle both system error returns and Berkeley DB-specific
return values.
</p>
<p>
For example:
</p>
<a id="prog_env29"></a>
<pre class="programlisting">int ret;
if ((ret = dbenv->set_cachesize(dbenv, 0, 32 * 1024, 1)) != 0) {
fprintf(stderr, "set_cachesize failed: %s\n", db_strerror(ret));
return (1);
}
</pre>
<p>
There are also two additional error methods: <a href="../api_reference/C/enverr.html" class="olink">DB_ENV->err()</a> and
<code class="methodname">DB_ENV->errx()</code>. These methods
work like the 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/enverr.html" class="olink">DB_ENV->err()</a> function appends the standard error string to
the constructed message; the
<code class="methodname">DB_ENV->errx()</code> function does
not.
</p>
<p>
Error messages can be configured always to include a prefix
(for example, the program name) using the <a href="../api_reference/C/envset_errpfx.html" class="olink">DB_ENV->set_errpfx()</a>
method.
</p>
<p>
These functions provide simpler ways of displaying Berkeley
DB error messages:
</p>
<a id="prog_env30"></a>
<pre class="programlisting">int ret;
...
dbenv->set_errpfx(dbenv, program_name);
if ((ret = dbenv->open(dbenv, home,
DB_CREATE | DB_INIT_LOG | DB_INIT_TXN | DB_USE_ENVIRON, 0))
!= 0) {
dbenv->err(dbenv, ret, "open: %s", home);
dbenv->errx(dbenv,
"contact your system administrator: session ID was %d",
session_id);
return (1);
}</pre>
<p>
For example, if the program was called "my_app", and it
tried to open an environment home directory in "/tmp/home" and
the open call returned a permission error, the error messages
shown would look like this:
</p>
<pre class="programlisting">my_app: open: /tmp/home: Permission denied.
my_app: contact your system administrator: session ID was 2</pre>
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