Library Version 18.1.40

Error support
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## Error support

Berkeley DB offers programmatic support for displaying error return values. The db_strerror() function returns a pointer to the error message corresponding to any Berkeley DB error return. This is similar to the ANSI C strerror interface, but can handle both system error returns and Berkeley DB-specific return values.

For example:

    int ret;
    if ((ret = dbenv->set_cachesize(dbenv, 0, 32 * 1024, 1)) != 0) {
        fprintf(stderr, "set_cachesize failed: %s\n", db_strerror(ret));
        return (1);
    }

There are also two additional error methods: DB_ENV->err() and `DB_ENV->errx()`. These methods work like the ANSI C printf function, taking a printf-style format string and argument list, and writing a message constructed from the format string and arguments.

The DB_ENV->err() function appends the standard error string to the constructed message; the `DB_ENV->errx()` function does not.

Error messages can be configured always to include a prefix (for example, the program name) using the DB_ENV->set_errpfx() method.

These functions provide simpler ways of displaying Berkeley DB error messages:

    int ret;
    ...
    dbenv->set_errpfx(dbenv, program_name);
    if ((ret = dbenv->open(dbenv, home,
        DB_CREATE | DB_INIT_LOG | DB_INIT_TXN | DB_USE_ENVIRON, 0))
        != 0) {
        dbenv->err(dbenv, ret, "open: %s", home);
        dbenv->errx(dbenv,
            "contact your system administrator: session ID was %d",
            session_id);
        return (1);
    }

For example, if the program was called "my_app", and it tried to open an environment home directory in "/tmp/home" and the open call returned a permission error, the error messages shown would look like this:

    my_app: open: /tmp/home: Permission denied.
    my_app: contact your system administrator: session ID was 2

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