int aio_read(struct aiocb *aiocbp);
The aio_read() function shall read aiocbp->aio_nbytes from the file associated with aiocbp->aio_fildes into the buffer pointed to by aiocbp->aio_buf. The function call shall return when the read request has been initiated or queued to the file or device (even when the data cannot be delivered immediately).
If prioritized I/O is supported for this file, then the asynchronous operation shall be submitted at a priority equal to the scheduling priority of the process minus aiocbp->aio_reqprio.
The aiocbp value may be used as an argument to aio_error() and aio_return() 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 shall return 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() were called immediately prior to the operation with an offset equal to aio_offset and a whence equal to SEEK_SET. After a successful call to enqueue an asynchronous I/O operation, the value of the file offset for the file is unspecified.
The aiocbp->aio_lio_opcode field shall be ignored by aio_read().
The aiocbp argument points to an aiocb structure. If the buffer pointed to by aiocbp->aio_buf or the control block pointed to by aiocbp becomes an illegal address prior to asynchronous I/O completion, then the behavior is undefined.
Simultaneous asynchronous operations using the same aiocbp produce undefined results.
If synchronized I/O is enabled on the file associated with aiocbp->aio_fildes, the behavior of this function shall be according to the definitions of synchronized I/O data integrity completion and synchronized I/O file integrity completion.
For any system action that changes the process memory space while an asynchronous I/O is outstanding to the address range being changed, the result of that action is undefined.
For regular files, no data transfer shall occur past the offset maximum established in the open file description associated with aiocbp->aio_fildes.
The aio_read() function shall return the value zero to the calling process if the I/O operation is successfully queued; otherwise, the function shall return the value -1 and set errno to indicate the error.
The aio_read() function shall fail if:
Each of the following conditions may be detected synchronously at the time of the call to aio_read(), or asynchronously. If any of the conditions below are detected synchronously, the aio_read() function shall return -1 and set errno to the corresponding value. If any of the conditions below are 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.
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:
The following condition may be detected synchronously or asynchronously:
The following sections are informative.
The aio_read() function is part of the Asynchronous Input and Output option and need not be available on all implementations.
aio_cancel() , aio_error() , lio_listio() , aio_return() , aio_write() , close() , exec() , exit() , fork() , lseek() , read() , the Base Definitions volume of IEEE Std 1003.1-2001, <aio.h>