READAHEAD(2) Linux Programmer's Manual READAHEAD(2)NAMEreadahead - perform file readahead into page cache
SYNOPSIS
#include <fcntl.h>
ssize_t readahead(int fd, off64_t *offset, size_t count);
DESCRIPTIONreadahead() populates the page cache with data from a file so that sub‐
sequent reads from that file will not block on disk I/O. The fd argu‐
ment 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.
CONFORMING TO
The readahead() system call is Linux specific, and its use should be
avoided in portable applications.
NOTES
The readahead() system call appeared in Linux 2.4.13.
SEE ALSOfadvise(2), lseek(2), madvise(2), mmap(2), posix_fadvise(2), read(2)Linux 2.6.5 2004-10-05 READAHEAD(2)
