POSIX_FADVISE(2)					      BSD System Calls Manual						  POSIX_FADVISE(2)

NAME

     posix_fadvise -- give advice about use of file data

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <fcntl.h>

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

DESCRIPTION

     The posix_fadvise() system call allows a process to describe to the system its data access behavior for an open file descriptor fd.  The
     advice covers the data starting at offset offset and continuing for len bytes.  If len is zero, all data from offset to the end of the file
     is covered.

     The behavior is specified by the advice parameter and may be one of:

     POSIX_FADV_NORMAL	    Tells the system to revert to the default data access behavior.

     POSIX_FADV_RANDOM	    Is a hint that file data will be accessed randomly, and prefetching is likely not advantageous.

     POSIX_FADV_SEQUENTIAL  Tells the system that file data will be accessed sequentially.  This currently does nothing as the default behavior
			    uses heuristics to detect sequential behavior.

     POSIX_FADV_WILLNEED    Tells the system that the specified data will be accessed in the near future.  The system may initiate an asynchronous
			    read of the data if it is not already present in memory.

     POSIX_FADV_DONTNEED    Tells the system that the specified data will not be accessed in the near future.  The system may decrease the in-mem-
			    ory priority of clean data within the specified range and future access to this data may require a read operation.

     POSIX_FADV_NOREUSE     Tells the system that the specified data will only be accessed once and then not reused.  The system may decrease the
			    in-memory priority of data once it has been read or written.  Future access to this data may require a read operation.

RETURN VALUES

     The posix_fadvise() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to
     indicate the error.

ERRORS

     The posix_fadvise() system call returns zero on success, and an error on failure:

     [EBADF]		The fd argument is not a valid file descriptor.

     [EINVAL]		The advice argument is not valid.

     [EINVAL]		The offset or len arguments are negative, or offset + len is greater than the maximum file size.

     [ENODEV]		The fd argument does not refer to a regular file.

     [ESPIPE]		The fd argument is associated with a pipe or FIFO.

SEE ALSO

     madvise(2)

STANDARDS

     The posix_fadvise() interface conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

HISTORY

     The posix_fadvise() system call first appeared in FreeBSD 9.1.

BSD
								 January 30, 2014							       BSD