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db_env_set_func_ioinfo
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## db_env_set_func_ioinfo

    #include <db.h>

    int
    db_env_set_func_ioinfo(int (*func_ioinfo)(const char *path,
        int fd, u_int32_t *mbytesp, u_int32_t *bytesp, u_int32_t *iosizep));

The Berkeley DB library requires the ability to determine the size and I/O characteristics of a file.

The `db_env_set_func_ioinfo()` function configures all operations performed by a process and all of its threads of control, not operations confined to a single database environment.

Although the `db_env_set_func_ioinfo()` function may be called at any time during the life of the application, it should normally be called before making calls to the db_env_create or db_create methods.

The `db_env_set_func_ioinfo()` function returns a non-zero error value on failure and 0 on success.

### Parameters

#### func_ioinfo

The func_ioinfo parameter is the function which returns the size and I/O characteristics of a file.

The path parameter is the pathname of the file to be checked, and the fd parameter is an open file descriptor on the file.

If the mbytesp and bytesp parameters are non-NULL, the ioinfo function must return in them the size of the file: the number of megabytes in the file into the memory location to which the mbytesp parameter refers, and the number of bytes over and above that number of megabytes into the memory location to which the bytesp parameter refers.

In addition, if the iosizep parameter is non-NULL, the ioinfo function must return the optimum granularity for I/O operations to the file into the memory location to which it refers.

The func_ioinfo function must return the value of errno on failure and 0 on success.

### See Also

Run-time configuration

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