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 sta-
       tus 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 er-
       rno, 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  in-
              valid.

       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 at-
       tributes(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  con-
       trol block must not be changed while the read operation is in progress.
       The buffer area being read into must not be accessed during the  opera-
       tion  or  undefined  results may occur.  The memory areas involved must
       remain valid.

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

EXAMPLE
       See aio(7).

SEE ALSO
       aio_cancel(3),   aio_error(3),  aio_fsync(3),  aio_return(3),  aio_sus-
       pend(3), aio_write(3), lio_listio(3), aio(7)

COLOPHON
       This page is part of release 5.05 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/.

                                  2017-09-15                       AIO_READ(3)