aio_read(S)
aio_read --
asynchronous read
Syntax
cc . . . -lsuds
#include <aio.h>
int aio_read (struct aiocb *aiocbp);
Description
The aiocbp argument points to an aiocb
structure. The
aio_read(S)
function allows the calling process to read
aiocbp->aio_nbytes from the file associated with
aiocbp->aio_fildes into the buffer pointed to by
aiocbp->aiobuf (see
read(S)).
aiocbp->aio_fildes must refer to a raw device,
aiocbp->aio_nbytes must be a multiple of 512, and
aiocbp->aio_buf must be 512-byte aligned.
The function call returns when the read request has been initiated
or queued to the file or device (even when the data cannot be
delivered immediately).
The aiocbp value may be used as an argument to
aio_error(S)
and
aio_return(S)
in order to determine the error status and return status,
respectively, of the asynchronous operation while it is
proceeding. If an error condition is encountered during queuing, the
function call returns without having initiated or queued the
request. The requested operation takes place at the absolute
position in the file as given by aio_offset, as if
lseek(S)
were called immediately prior to the operation with an
offset equal to aio_offset, and a
whence equal to SEEK_SET. aio_offset
must be a multiple of 512.
The aiocbp->aio_lio_opcode field is ignored by
aio_read.
Return values
The aio_read function returns the value zero to the
calling process if the I/O operation is successfully
queued; otherwise, the function returns the value -1 and sets
errno to indicate the error.
Diagnostics
If the following condition occurs, the aio_read function
returns -1 and sets errno to the corresponding value:
[EAGAIN]-
The requested asynchronous I/O operation was not queued
due to system resource limitations.
Each of the following conditions may be detected synchronously at
the time of the call to aio_read, or asynchronously. If
either of the conditions below is detected synchronously, the
aio_read function returns -1 and sets errno
to the corresponding value. If either of the conditions below is
detected asynchronously, the return status of the asynchronous
operation is set to -1 and the error status of the asynchronous
operation is set to the corresponding value.
[EBADF]-
The
aiocbp->aio_fildes argument is not a valid file
descriptor open for reading.
[EINVAL]-
The file offset value implied by
aiocbp->aio_offset
would be invalid, aiocbp->aio_reqprio is not a valid
value, aiocbp->aio_nbytes is an invalid value, or
aiocbp->aio_buf is invalid.
In the case that the aio_read successfully queues the
I/O operation but the operation is subsequently canceled
or encounters an error, the return status of the asynchronous
operation is one of the values normally returned by the
read function call. In addition, the error status of the
asynchronous operation is set to one of the error statuses normally
set by the read function call, or one of the following
values:
[EBADF]-
The
aiocbp->aio_fildes argument is not a valid file
descriptor open for reading.
[EINVAL]-
The file offset value implied by
aiocbp->aio_offset
would be invalid.
See also
aio(FP),
aio_error(S),
aio_mkcbs(S),
aio_return(S),
aio_write(S),
close(S),
_exit(S),
exec(S),
fork(S),
lio_listio(S),
lseek(S),
read(S)
Standards conformance
Text reprinted and/or adapted from IEEE Std 1003.1b-1993,
IEEE Standard for Information Technology, POSIX
Part 1: System Application Program Interface (API)
Amendment 1: Realtime Extensions [C Language], copyright © 1993
by the Institute of Electrical and Electronics Engineers, Inc. The
IEEE takes no responsibility for and will assume no
liability for damages resulting from the reader's misinterpretation
of said information resulting from the placement and context in this
publication. Information is reproduced with the permission of the
IEEE.
© 2003 System Services (S)
SCO OpenServer Release 5.0.7 -- 11 February 2003