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<h2 class="title" style="clear: both"><a id="db_get"></a><span class="emphasis"><em>db</em></span> get</h2>
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<pre class="programlisting">db get
[-consume]
[-consume_wait]
[-glob]
[-partial {doff dlen}]
[-recno]
[-rmw]
[-txn txnid]
key
db get
-get_both
[-partial {doff dlen}]
[-rmw]
[-txn txnid]
key data </pre>
<p>
The <span class="emphasis"><em>db</em></span> <span class="bold"><strong>get</strong></span>
command returns key/data pairs from the database.
</p>
<p>
In the presence of duplicate key values, <span class="emphasis"><em>db</em></span>
<span class="bold"><strong>get</strong></span> will return all duplicate items.
Duplicates are sorted by insert order except where this order has been
overridden by cursor operations.
</p>
<p>
The options are as follows:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<span class="bold"><strong>-consume</strong></span>
</p>
<p>
Return the record number and data from the available record closest to
the head of the queue, and delete the record. The cursor will be
positioned on the deleted record. A record is available if it is not
deleted and is not currently locked. The underlying database must be
of type Queue for <span class="bold"><strong>-consume</strong></span> to be
specified.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-consume_wait</strong></span>
</p>
<p>
The same as the <span class="bold"><strong>-consume</strong></span> flag except
that if the Queue database is empty, the thread of control will wait
until there is data in the queue before returning. The underlying
database must be of type Queue for <span class="bold"><strong>-consume_wait</strong></span> to be specified.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-get_both key data</strong></span>
</p>
<p>
Retrieve the key/data pair only if both the key and data match the
arguments.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-glob</strong></span>
</p>
<p>
Return all keys matching the given key, where the key is a simple
wildcard pattern. Where it is used, it replaces the use of the key
with the given pattern of a set of keys. Any characters after the
wildcard character are ignored. For example, in a database of last
names, the command "db0 get Jones" will return all occurrences of
"Jones" in the database, and the command "db0 get -glob Jo*" will
return both "Jones" and "Johnson" from the database. The command "db0
get -glob *" will return all of the key/data pairs in the database.
This option only works on databases using the Btree access method.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-partial {doff dlen}</strong></span>
</p>
<p>
The <span class="bold"><strong>dlen</strong></span> bytes starting <span class="bold"><strong>doff</strong></span> bytes from the beginning of the retrieved
data record are returned as if they comprised the entire record. If
any or all of the specified bytes do not exist in the record, the
command is successful and any existing bytes are returned.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-recno</strong></span>
</p>
<p>
Retrieve the specified numbered key/data pair from a database. For
<span class="bold"><strong>-recno</strong></span> to be specified, the specified
key must be a record number; and the underlying database must be of
type Recno or Queue, or of type Btree that was created with the
<span class="bold"><strong>-recnum</strong></span> option.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-rmw</strong></span>
</p>
<p>
Acquire write locks instead of read locks when doing the retrieval.
Setting this flag may decrease the likelihood of deadlock during a
read-modify-write cycle by immediately acquiring the write lock during
the read part of the cycle so that another thread of control acquiring
a read lock for the same item, in its own read-modify-write cycle,
will not result in deadlock.
</p>
<p>
Because the <span class="emphasis"><em>db</em></span> <span class="bold"><strong>get</strong></span> command will not hold locks across Berkeley
DB interface calls in nontransactional environments, the <span class="bold"><strong>-rmw</strong></span> argument to the <span class="emphasis"><em>db</em></span>
<span class="bold"><strong>get</strong></span> call is only meaningful in the
presence of transactions.
</p>
</li>
<li>
<p>
<span class="bold"><strong>-txn txnid</strong></span>
</p>
<p>
If the operation is part of an application-specified transaction, the
<span class="bold"><strong>txnid</strong></span> parameter is a transaction
handle returned from <span class="emphasis"><em>env</em></span> <span class="bold"><strong>txn</strong></span>. If no transaction handle is specified,
but the operation occurs in a transactional database, the operation
will be implicitly transaction protected.
</p>
</li>
</ul>
</div>
<p>
If the underlying database is a Queue or Recno database, the given key
will be interpreted by Tcl as an integer. For all other database
types, the key is interpreted by Tcl as a byte array, unless indicated
by a given option.
</p>
<p>
A list of key/data pairs is returned. In the error case that no
matching key exists, an empty list is returned. In all other cases, a
Tcl error is thrown.
</p>
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