# DB_ENV->err

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    #include <db.h>

    void
    DB_ENV->err(DB_ENV *dbenv, int error, const char *fmt, ...);

    void
    DB_ENV->errx(DB_ENV *dbenv, const char *fmt, ...);

# Description

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

The DB_ENV->err function constructs 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 function, any prefix string specified using the DB_ENV->set_errpfx function, 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 arguments 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 function.

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 arguments: 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 has been configured, the error message is written to stderr, the standard error output stream.

The DB_ENV->errx and DB->errx functions perform identically to the DB_ENV->err and DB->err functions, except that they do not append the final separator characters and standard error string to the error message.

# See Also

db_env_create, DB_ENV->close, DB_ENV->err, DB_ENV->errx DB_ENV->open, DB_ENV->remove, DB_ENV->set_alloc, DB_ENV->set_cachesize, DB_ENV->set_data_dir, DB_ENV->set_errcall, DB_ENV->set_errfile, DB_ENV->set_errpfx, DB_ENV->set_feedback, DB_ENV->set_flags, DB_ENV->set_mutexlocks, db_env_set_pageyield, DB_ENV->set_paniccall, db_env_set_panicstate, DB_ENV->set_recovery_init, DB_ENV->set_rpc_server, db_env_set_region_init, DB_ENV->set_shm_key, db_env_set_tas_spins, DB_ENV->set_tmp_dir, DB_ENV->set_verbose, db_strerror and db_version.`

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