### DbEnv::log_printf

`

###

    #include <db_cxx.h>

    int
    DbEnv::log_printf(DB_TXN *txnid, const char *fmt, ...);

### Description: DbEnv::log_printf

The DbEnv::log_printf method appends an informational message to the Berkeley DB database environment log files.

The DbEnv::log_printf method allows applications to include information in the database environment log files, for later review using the db_printlog utility. This method is intended for debugging and performance tuning.

The DbEnv::log_printf method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

### Parameters

txnid
  If the logged message refers to an application-specified transaction, the txnid parameter is a transaction handle returned from DbEnv::txn_begin; otherwise NULL.
fmt
  A format string that specifies how subsequent arguments (or arguments accessed via the variable-length argument facilities of stdarg(3)) are converted for output. The format string may contain any formatting directives supported by the underlying C library vsnprintf(3) function.

### Errors

The DbEnv::log_printf method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL
  An invalid flag value or parameter was specified.

### Class

DbEnv, DbLogc, DbLsn

### See Also

Logging Subsystem and Related Methods`

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