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io_cancel

Section: Linux AIO (2)
Updated: 2002-09-03
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NAME

io_cancel - Cancel io requests

SYNOPSIS

#include <errno.h>



#include <libaio.h>



int io_cancel(io_context_t ctx, struct iocb *iocb)



struct iocb {
        void            *data; /* Return in the io completion event */
        unsigned        key;    /* For use in identifying io requests */
        short           aio_lio_opcode;
        short           aio_reqprio;    /* Not used */
        int             aio_fildes;
};

DESCRIPTION

Attempts to cancel an iocb previously passed to io_submit. If the operation is successfully cancelled, the resulting event is copied into the memory pointed to by result without being placed into the completion queue.

When one or more requests are asynchronously processed, it might be useful in some situations to cancel a selected operation, e.g., if it becomes obvious that the written data is no longer accurate and would have to be overwritten soon. As an example, assume an application, which writes data in files in a situation where new incoming data would have to be written in a file which will be updated by an enqueued request.

RETURN VALUES

0 is returned on success , otherwise returns Errno.

ERRORS

EFAULT: If any of the data structures pointed to are invalid.
EINVAL: If aio_context specified by ctx_id is invalid.
EAGAIN: If the iocb specified was not cancelled.
ENOSYS: if not implemented.