Berkeley DB

Retrieving Elements from a Database

The simplest way to retrieve elements from a database is using the DB→get interface. It takes the same five arguments as the DB→put interface:

• db: The database handle returned by db_create.

• txnid: A transaction ID. In our simple case, we don’t expect to recover the database after an application or system crash, so we aren’t using transactions and will leave this argument NULL.

• key: The key item for the key/data pair that we want to retrieve from the database.

• data: The data item for the key/data pair that we want to retrieve from the database.

• flags: Optional flags that modify the underlying behavior of the DB→get interface.

Here’s what the code to call DB→get looks like:

 #include <sys/types.h> #include ...