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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 struc‐
       ture.)

       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 unspeci‐
       fied.

       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 com‐
       pletion 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 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 statusβ€”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).

       β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
       β”‚Interface                                                                                                                             β”‚ Attribute     β”‚ Value   β”‚
       β”œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”Όβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”Όβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€
       β”‚aio_read()                                                                                                                            β”‚ Thread safety β”‚ MT-Safe β”‚
       β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

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 be‐
       ing 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)

                                                                               2021-03-22                                                                    AIO_READ(3)