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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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POSIX_FADVISE(3P) POSIX Programmer's Manual POSIX_FADVISE(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
posix_fadvise — file advisory information (ADVANCED REALTIME)
#include <fcntl.h>
int posix_fadvise(int fd, off_t offset, off_t len, int advice);
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 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>.
Upon successful completion, posix_fadvise() shall return zero;
otherwise, an error number shall be returned to indicate the
error.
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.
The following sections are informative.
None.
The posix_fadvise() function is part of the Advisory Information
option and need not be provided on all implementations.
None.
None.
posix_madvise(3p)
The Base Definitions volume of POSIX.1‐2017, fcntl.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 POSIX_FADVISE(3P)
Pages that refer to this page: fcntl.h(0p), posix_madvise(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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