How to convert berkeley db files into CSV/JSON?

Berkeley DB's data records are stored in a binary format defined by the particular application that uses it. There's no way to universally dump records in a way like you would with a traditional SQL database.

If you know how the keys and data are formatted by the application, then you can use the db_dump utility to generate a hexadecimal dump of the database. Then, you can parse that and break the records down into something that you can put in JSON.

For example, you might have an application that stored the contents of your shopping cart in each record: milk, eggs, and bread. In JSON, that would break down into something like { "milk": 5, "eggs": 24, "bread": 1 }.

But in BDB, it might be something like the following C struct:

struct {
    uint32_t milk;
    uint32_t eggs;
    uint32_t bread;
} record;

Each record would be 12 bytes long. The first four are milk, perhaps in little-endian format. The next four are eggs. And, so on. When you use db_dump on this, it'll just output 12 hexadecimal bytes. It's on you to parse what those bytes mean.