aiocb(5)

Synopsis

   

   cc [options] -Kthread file
   

   #include <aio.h>

Description

The asynchronous I/O routines pass information with the request and receive completion status information after the I/O operation has completed. An asynchronous I/O control block structure aiocb is used to specify input parameters and receive completion status information for asynchronous I/O requests. This structure is defined in aio.h and includes the following members:

      int             aio_fildes;      /* file descriptor          */
      volatile void  *aio_buf;         /* buffer location          */
      size_t          aio_nbytes;      /* length of transfer       */
      off_t           aio_offset;      /* file offset              */
      int             aio_reqprio;     /* request priority offset  */
      struct sigevent aio_sigevent;    /* signal number and offset */
      int             aio_lio_opcode;  /* listio operation         */
      int             aio_flags;       /* flags                    */

The structure members aio_fildes, aio_buf, and aio_nbytes are the same as the fildes, buf, and nbytes arguments to read and write. With aio_read, for example, the caller wishes to read aio_nbytes from the file associated with aio_fildes into the buffer pointed to by aio_buf. All appropriate structure members should be set by the caller when aio_read or aio_write is called.

The aio_sigevent member defines the notification method to be used on I/O completion. If aio_sigevent.sigev_notify is SIGEV_NONE, no notification is posted on I/O completion, but the error status for the operation and the return status for the operation shall be appropriately set.

You may set the AIO_RAW flag bit in the aio_flags structure member when the asynchronous I/O is being done to a raw device partition. When the AIO_RAW flag bit is set, asynchronous I/O might possibly be more efficient.

To insure forward compatibility, you must set all unused fields of the aiocb structure to zero. This can be done by using calloc [see malloc(3C)] to allocate the structure. The aio_reqprio and aio_lio_opcode fields should be set to zero.

aiocb also specifies the asynchronous I/O control block that is used by the 64 bit versions of the asynchronous I/O interface routines. This structure, aiocb64, includes the following members:

   struct aiocb64
           int             aio_fildes;
           volatile void   *aio_buf;
           size_t          aio_nbytes;
           off64_t         aio_offset;
           int             aio_reqprio;
           struct sigevent aio_sigevent;
           int             aio_lio_opcode;
           int             aio_flags;

References

Notices