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

NAME

       readahead - perform file readahead into page cache

SYNOPSIS

       #define _GNU_SOURCE
       #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).  readahead() 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.

SEE ALSO

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

COLOPHON

       This page is part of release 3.25 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								    2007-07-26							      READAHEAD(2)