NAME

       io_uring_prep_read - prepare I/O read request

SYNOPSIS

       #include <liburing.h>

       void io_uring_prep_read(struct io_uring_sqe *sqe,
                               int fd,
                               void *buf,
                               unsigned nbytes,
                               __u64 offset);

DESCRIPTION

       The  io_uring_prep_read(3)  prepares an IO read request. The submission queue entry sqe is
       setup to use the file descriptor fd to start reading nbytes into the  buffer  buf  at  the
       specified offset.

       On files that support seeking, if the offset is set to -1, the read operation commences at
       the file offset, and the file offset is incremented by  the  number  of  bytes  read.  See
       read(2)  for  more  details.  Note that for an async API, reading and updating the current
       file offset may result in unpredictable behavior, unless access to the file is serialized.
       It  is  not  encouraged  to  use  this feature, if it's possible to provide the desired IO
       offset from the application or library.

       On files that are not capable of seeking, the offset must be 0 or -1.

       After the read has been prepared it can be submitted with one of the submit functions.

RETURN VALUE

       None

ERRORS

       The CQE res field will contain the result of the operation. See the related man  page  for
       details  on  possible  values.  Note that where synchronous system calls will return -1 on
       failure and set errno to the actual error value, io_uring never uses  errno.   Instead  it
       returns the negated errno directly in the CQE res field.

SEE ALSO

       io_uring_get_sqe(3), io_uring_prep_readv(3), io_uring_prep_readv2(3), io_uring_submit(3)