aio_read(2)							System Calls Manual						       aio_read(2)

NAME

       aio_read() - start an asynchronous read operation

SYNOPSIS

DESCRIPTION

       The  function allows the calling process to perform an asynchronous read from a previously opened file.	The function call returns when the
       read operation has been enqueued for processing.  At this point, processing of the read operation may proceed concurrently  with  execution
       of the calling process or thread.

       If  an  error condition is detected that prevents the read request from being enqueued, returns and sets to indicate the cause of the fail-
       ure.  Once the read operation has been successfully enqueued, an and function referencing the referred to by must be used to determine  its
       status  and  any  error	conditions,  including	those  normally  reported  by The request remains enqueued and consumes process and system
       resources until is called.

       The function allows the calling process to read from the file associated with into the buffer pointed to by The priority of the read opera-
       tion  is  reduced  by the value of which must be a value between 0 (zero) and a maximum value which can be obtained using the call with the
       argument A value of 0 (zero) yields no reduction in priority.  The field is ignored.

       The read operation takes place at the absolute position in the file given by as if were called immediately  prior  to  the  operation  with
       equal to and set to However, the value of the file offset is never changed by asynchronous I/O operations.

       Deallocating  or  altering  the contents of memory referred to by while an asynchronous read operation is outstanding (i.e. before has been
       called) may produce unpredictable results.

       If is a valid signal event structure, then the designated signal will be delivered when the  requested  asynchronous  read  operation  com-
       pletes.

       To use this function, link in the realtime library by specifying on the compiler or linker command line.

RETURN VALUE

       returns the following values:

	      Successful completion, the operation has been enqueued.

	      Failure.	     The requested operation was not enqueued.	is set to indicate the error.

       The  return  value from reflects the success or failure of enqueuing the requested read operation for asynchronous processing.  fails if an
       error in the function call is immediately detected, or if system resource limits prevent the request from being enqueued.  Other error con-
       ditions are reported asynchronously and must be retrieved with and

ERRORS

       If detects one of the following error conditions, is set to the indicated value:

	      The request could not be queued either because of a resource shortage
			     or  because  the  per-process  or system-wide limit on asynchronous I/O operations or asynchronous threads would have
			     been exceeded.

	      is not a valid address in the process virtual address space.

	      The parameters of the indicated
			     in are invalid.

	      The	     is already in use for another asynchronous I/O operation.

       Once the read request has been enqueued by the following errors, in addition to all of the errors normally reported by the function, may be
       reported asynchronously by a subsequent call to or referencing its

	      The	     was not a valid file descriptor open for reading.

	      The value of   is not valid.

	      The value of   is invalid.

	      The file offset implied by
			     or are not valid for the file at the time the request is processed.

	      The read operation was canceled due to a subsequent
			     call to

EXAMPLES

       The following code sequence and call to starts an asynchronous read operation.

SEE ALSO

       aio_cancel(2), aio_error(2), aio_fsync(2), aio_return(2), aio_suspend(2), aio_write(2), lio_listio(2), read(2), aio(5).

STANDARDS CONFORMANCE

																       aio_read(2)