NAME

posix_fadvise — file advisory information (ADVANCED REALTIME)

SYNOPSIS

[ADV] #include <fcntl.h>

int posix_fadvise(int fd, off_t offset, off_t len, int advice);

DESCRIPTION

The posix_fadvise() function shall advise the implementation on the expected behavior of the application with respect to the data in the file associated with the open file descriptor, fd, starting at offset and continuing for len bytes. The specified range need not currently exist in the file. If len is zero, all data from offset to the largest possible value of the file offset for that file shall be specified. The implementation may use this information to optimize handling of the specified data. The posix_fadvise() function shall have no effect on the semantics of other operations on the specified data, although it may affect the performance of other operations.

The advice to be applied to the data is specified by the advice parameter and may be one of the following values:

POSIX_FADV_NORMAL

Specifies that the application has no advice to give on its behavior with respect to the specified data. It is the default characteristic if no advice is given for an open file.

POSIX_FADV_SEQUENTIAL

Specifies that the application expects to access the specified data sequentially from lower offsets to higher offsets.

POSIX_FADV_RANDOM

Specifies that the application expects to access the specified data in a random order.

POSIX_FADV_WILLNEED

Specifies that the application expects to access the specified data in the near future.

POSIX_FADV_DONTNEED

Specifies that the application expects that it will not access the specified data in the near future.

POSIX_FADV_NOREUSE

Specifies that the application expects to access the specified data once and then not reuse it thereafter.

These values are defined in <fcntl.h>.

RETURN VALUE

Upon successful completion, posix_fadvise() shall return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS

The posix_fadvise() function shall fail if:

[EBADF]

The fd argument is not a valid file descriptor.

[EINVAL]

The value of advice is invalid, or the value of len is less than zero.

[ESPIPE]

The fd argument is associated with a pipe or FIFO.

EXAMPLES

None.

APPLICATION USAGE

The posix_fadvise() function is part of the Advisory Information option and need not be provided on all implementations.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

posix_madvise

XBD <fcntl.h>

CHANGE HISTORY

First released in Issue 6. Derived from IEEE Std 1003.1d-1999.

In the SYNOPSIS, the inclusion of <sys/types.h> is no longer required.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/68 is applied, changing the function prototype in the SYNOPSIS section. The previous prototype was not large file-aware, and the standard developers felt it acceptable to make this change before implementations of this function become widespread.

Issue 7

Austin Group Interpretation 1003.1-2001 #024 is applied, changing the definition of the [EINVAL] error.

Issue 8

Austin Group Defect 1135 is applied, clarifying the requirements when len is zero.