aio_read

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



NAME
       aio_read - asynchronous read

SYNOPSIS
       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

       Link with -lrt.

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(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.

RETURN VALUE
       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).

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.

VERSIONS
       The aio_read() function is available since glibc 2.1.

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

       ┌───────────┬───────────────┬─────────┐
       │Interface  Attribute     Value   │
       ├───────────┼───────────────┼─────────┤
       │aio_read() │ Thread safety │ MT-Safe │
       └───────────┴───────────────┴─────────┘
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

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)

COLOPHON
       This page is part of release 5.08 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
       https://www.kernel.org/doc/man-pages/.



                                  2020-06-09                       AIO_READ(3)