plucky (3) io_uring_prep_read.3.gz

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)