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<title>Berkeley DB Reference Guide: Error returns</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Simple Tutorial</dl></h3></td>
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<h1 align=center>Error returns</h1>
<p>The Berkeley DB interfaces always return a value of 0 on success. If the
operation does not succeed for any reason, the return value will be
non-zero.
<p>If a system error occurred (for example, Berkeley DB ran out of disk space,
or permission to access a file was denied, or an illegal argument was
specified to one of the interfaces), Berkeley DB returns an <b>errno</b>
value. All of the possible values of <b>errno</b> are greater than
0.
<p>If the operation didn't fail due to a system error, but wasn't
successful either, Berkeley DB returns a special error value. For example,
if you tried to retrieve the data item associated with the key
<b>fruit</b>, and there was no such key/data pair in the database,
Berkeley DB would return <a href="../../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a>, a special error value that means
the requested key does not appear in the database. All of the possible
special error values are less than 0.
<p>Berkeley DB also offers programmatic support for displaying error return values.
First, 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>Second, there are two error functions, <a href="../../api_c/db_err.html">DB->err</a> and <a href="../../api_c/db_err.html">DB->errx</a>.
These functions work like the ANSI C printf interface, taking a
printf-style format string and argument list, and optionally appending
the standard error string to a message constructed from the format string
and other arguments.
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