aio_read(3)                                           Library Functions Manual                                          aio_read(3)

       aio_read - asynchronous read

       Real-time library (librt, -lrt)

       #include <aio.h>

       int aio_read(struct aiocb *aiocbp);

       The aio_read() function queues the I/O request described by the buffer pointed to by aiocbp.  This function is the asynchro‐
       nous 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  com‐
       pleted  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 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 sta‐
       tus—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 valid.

       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)

Linux man-pages 6.03                                         2023-02-05                                                 aio_read(3)