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Linux 2.6 - man page for readahead (linux section 2)

READAHEAD(2)			    Linux Programmer's Manual			     READAHEAD(2)

NAME
       readahead - perform file readahead into page cache

SYNOPSIS
       #define _GNU_SOURCE	       /* See feature_test_macros(7) */
       #include <fcntl.h>

       ssize_t readahead(int fd, off64_t offset, size_t count);

DESCRIPTION
       readahead()  populates  the page cache with data from a file so that subsequent reads from
       that file will not block on disk I/O.  The fd argument is a  file  descriptor  identifying
       the file which is to be read.  The offset argument specifies the starting point from which
       data is to be read and count specifies the number of bytes to be read.  I/O  is	performed
       in  whole  pages,  so that offset is effectively rounded down to a page boundary and bytes
       are read up to the next page boundary greater than or  equal  to  (offset+count).   reada-
       head()  does  not read beyond the end of the file.  readahead() blocks until the specified
       data has been read.  The current file offset of the open file referred to by  fd  is  left
       unchanged.

RETURN VALUE
       On  success, readahead() returns 0; on failure, -1 is returned, with errno set to indicate
       the cause of the error.

ERRORS
       EBADF  fd is not a valid file descriptor or is not open for reading.

       EINVAL fd does not refer to a file type to which readahead() can be applied.

VERSIONS
       The readahead() system call appeared in Linux 2.4.13;  glibc  support  has  been  provided
       since version 2.3.

CONFORMING TO
       The  readahead()  system call is Linux-specific, and its use should be avoided in portable
       applications.

NOTES
       On some 32-bit architectures, the calling signature for this system call differs, for  the
       reasons described in syscall(2).

SEE ALSO
       lseek(2), madvise(2), mmap(2), posix_fadvise(2), read(2)

COLOPHON
       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

Linux					    2013-04-01				     READAHEAD(2)


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