DB->err()
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## DB->err()

    #include <db.h>

    void
    DB->err(DB *db, int error, const char *fmt, ...);

    void
    DB->errx(DB *db, const char *fmt, ...);

The DB_ENV->err(), `DB_ENV->errx()`, `DB->err()` and `DB->errx()` methods provide error-messaging functionality for applications written using the Berkeley DB library.

The `DB->err()` and DB_ENV->err() methods construct an error message consisting of the following elements:

- An optional prefix string

  If no error callback function has been set using the DB_ENV->set_errcall() method, any prefix string specified using the DB_ENV->set_errpfx() method, followed by two separating characters: a colon and a <space> character.

- An optional printf-style message

  The supplied message fmt, if non-NULL, in which the ANSI C X3.159-1989 (ANSI C) printf function specifies how subsequent parameters are converted for output.

- A separator

  Two separating characters: a colon and a <space> character.

- A standard error string

  The standard system or Berkeley DB library error string associated with the error value, as returned by the db_strerror method.

The `DB->errx()` and `DB_ENV->errx()` methods are the same as the `DB->err()` and DB_ENV->err() methods, except they do not append the final separator characters and standard error string to the error message.

This constructed error message is then handled as follows:

- If an error callback function has been set (see DB->set_errcall() and DB_ENV->set_errcall()), that function is called with two parameters: any prefix string specified (see DB->set_errpfx() and DB_ENV->set_errpfx()) and the error message.

- If a C library FILE * has been set (see DB->set_errfile() and DB_ENV->set_errfile()), the error message is written to that output stream.

- If none of these output options have been configured, the error message is written to stderr, the standard error output stream.

### Parameters

#### error

The error parameter is the error value for which the DB_ENV->err() and `DB->err()` methods will display an explanatory string.

#### fmt

The fmt parameter is an optional printf-style message to display.

### Class

DB

### See Also

Database and Related Methods

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