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