AIO_READ(3)                 Linux Programmer's Manual                AIO_READ(3)

       aio_read - asynchronous read

       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

       Link with -lrt.

       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(7) 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.

       On success, 0 is returned.  On error, the request is not enqueued, -1 is
       returned, and errno is set appropriately.  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).

       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.

              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.

       The aio_read() function is available since glibc 2.1.

       For an explanation of the terms used in this section, see attributes(7).

       │Interface  Attribute     Value   │
       │aio_read() │ Thread safety │ MT-Safe │
       POSIX.1-2001, POSIX.1-2008.

       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

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

       See aio(7).

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

       This page is part of release 5.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                   2020-06-09                        AIO_READ(3)