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posix_fadvise(2) [netbsd man page]

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

NAME
posix_fadvise -- hint at the future access pattern of a file LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/fcntl.h> int posix_fadvise(int fd, off_t offset, off_t size, int hint); DESCRIPTION
posix_fadvise() hints at the application's access pattern to the file and range given by the file descriptor, fd, and offset and size. If size is zero, it means to the end of file. hint should be one of the followings. POSIX_FADV_NORMAL No hint. (default) POSIX_FADV_RANDOM Random access. POSIX_FADV_SEQUENTIAL Sequential access. (from lower offset to higher offset.) POSIX_FADV_WILLNEED Will be accessed. POSIX_FADV_DONTNEED Will not be accessed. POSIX_FADV_NOREUSE Will be accessed just once. Calling posix_fadvise() doesn't alter the semantics of the operations, it is only a matter of performance. RETURN VALUES
On success, posix_fadvise() returns 0. Otherwise, it returns an error number. SEE ALSO
errno(2), madvise(2) BUGS
For POSIX_FADV_NORMAL, POSIX_FADV_RANDOM, and POSIX_FADV_SEQUENTIAL, the current implementation ignores offset and size, and applies the hint to the whole file. BSD
June 9, 2009 BSD

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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
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