POSIX_FADVISE(P) POSIX Programmer's Manual POSIX_FADVISE(P)NAMEposix_fadvise - file advisory information (ADVANCED REALTIME)
SYNOPSIS
#include <fcntl.h>
int posix_fadvise(int fd, off_t offset, size_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 following offset is speci‐
fied. 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 parame‐
ter 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; other‐
wise, 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.
ESPIPE The fd argument is associated with a pipe or FIFO.
The following sections are informative.
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 ALSOposix_madvise() , the Base Definitions volume of IEEE Std 1003.1-2001,
<fcntl.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 POSIX_FADVISE(P)
