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<h1>Db::fd</h1>
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<h3><pre>
#include <db_cxx.h>
<p>
int
Db::fd(int *fdp);
</pre></h3>
<h1>Description</h1>
<p>The Db::fd method
copies a file descriptor representative of the underlying database into
the memory to which <b>fdp</b> refers. A file descriptor referring to
the same file will be returned to all processes that call
<a href="../api_cxx/db_open.html">Db::open</a> with the same <b>file</b> argument. This file
descriptor may be safely used as an argument to the <b>fcntl</b>(2)
and <b>flock</b>(2) locking functions. The file descriptor is not
necessarily associated with any of the underlying files actually used
by the access method.
<p>The Db::fd method only supports a coarse-grained form of locking.
Applications should use the lock manager where possible.
<p>The Db::fd method either returns a non-zero error value or throws an exception that
encapsulates a non-zero error value on failure, and returns 0 on success.
<h1>Errors</h1>
<p>The Db::fd method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
If a catastrophic error has occurred, the Db::fd method may fail and
either return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw a
<a href="../api_cxx/runrec_class.html">DbRunRecoveryException</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>Class</h1>
<a href="../api_cxx/db_class.html">Db</a>
<h1>See Also</h1>
<a href="../api_cxx/db_list.html">Databases and Related Methods</a>
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