NAME

       aio_read - asynchronous read

LIBRARY

       Real-time library (librt, -lrt)

SYNOPSIS

       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

DESCRIPTION

       The  aio_read()  function  queues  the  I/O  request  described by the buffer pointed to by aiocbp.  This
       function is the asynchronous analog of read(2).  The arguments of the call

           read(fd, buf, count)

       correspond (in order) to the fields aio_fildes, aio_buf, and aio_nbytes of the structure  pointed  to  by
       aiocbp.  (See aio(7) for a description of the aiocb structure.)

       The  data  is  read  starting at the absolute position aiocbp->aio_offset, regardless of the file offset.
       After the call, the value of the file offset is unspecified.

       The "asynchronous" means that this call returns as soon as the request has been enqueued; the read may or
       may not have completed when the call returns.  One tests for completion using aio_error(3).   The  return
       status  of  a completed I/O operation can be obtained by aio_return(3).  Asynchronous notification of I/O
       completion can be  obtained  by  setting  aiocbp->aio_sigevent  appropriately;  see  sigevent(3type)  for
       details.

       If  _POSIX_PRIORITIZED_IO  is  defined,  and  this  file  supports it, then the asynchronous operation is
       submitted at a priority equal to that of the calling process minus aiocbp->aio_reqprio.

       The field aiocbp->aio_lio_opcode is ignored.

       No data is read from a regular file beyond its maximum offset.

RETURN VALUE

       On success, 0 is returned.  On error, the request is not enqueued, -1 is returned, and errno  is  set  to
       indicate  the  error.  If an error is detected only later, it will be reported via aio_return(3) (returns
       status -1) and aio_error(3) (error status—whatever one would have gotten in errno, such as EBADF).

ERRORS

       EAGAIN Out of resources.

       EBADF  aio_fildes is not a valid file descriptor open for reading.

       EINVAL One or more of aio_offset, aio_reqprio, or aio_nbytes are invalid.

       ENOSYS aio_read() is not implemented.

       EOVERFLOW
              The file is a regular file, we start reading before end-of-file and want at least  one  byte,  but
              the starting position is past the maximum offset for this file.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ aio_read()                                                                  │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       POSIX.1-2008.

HISTORY

       glibc 2.1.  POSIX.1-2001.

NOTES

       It  is a good idea to zero out the control block before use.  The control block must not be changed while
       the read operation is in progress.  The buffer area being read into  must  not  be  accessed  during  the
       operation or undefined results may occur.  The memory areas involved must remain valid.

       Simultaneous I/O operations specifying the same aiocb structure produce undefined results.

EXAMPLES

       See aio(7).

SEE ALSO

       aio_cancel(3),  aio_error(3),  aio_fsync(3),  aio_return(3), aio_suspend(3), aio_write(3), lio_listio(3),
       aio(7)

Linux man-pages 6.7                                2023-10-31                                        aio_read(3)