Asynchronously synchronize a file


#include <aio.h>

int aio_fsync( int op, 
               struct aiocb * aiocbptr );


One of the following:
  • O_DSYNC — complete all queued operations as if done by calling fdatasync() (i.e., as defined for synchronized I/O data integrity completion).
  • O_SYNC — complete all queued operations as if done by calling fsync() (i.e., as defined for synchronized I/O file integrity completion).
A pointer to an asynchronous I/O control block of type aiocb for which you want to asynchronously force all queued I/O operations to the synchronized I/O completion state.



Use the -l c option to qcc to link against this library. This library is usually included automatically.


The aio_fsync() function asynchronously forces all I/O operations associated with the file indicated by the file descriptor to the synchronized I/O completion state.

If the function succeeds, only the I/O operations that were queued at the time of the call are guaranteed to have been completed. The completion of subsequent I/O on the file descriptor isn't guaranteed to be completed in a synchronized fashion. If the operation that aio_fsync() queues fails, outstanding I/O operations aren't guaranteed to have been completed.

You can pass the aiocbptr argument to aio_error() or aio_return() to determine the error status and return status for the asynchronous operation.


0 if the I/O operation was successfully queued, or -1 if an error occurred (errno is set).


The requested asynchronous operation wasn't queued due to temporary resource limitations.
The aio_fildes member of the aiocb structure referenced by the aiocbptr argument isn't a valid file descriptor that's open for writing.
Synchronized I/O isn't supported for this file.
The op argument was something other than O_DSYNC or O_SYNC.

If any of the queued I/O operations failed, aio_fsync() returns the error condition defined for read() and write(). The error is returned in the error status for the asynchronous fsync() operation, which you can retrieve by using aio_error().


POSIX 1003.1

Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes


The first time you call an aio_* function, a thread pool is created, making your process multithreaded if it isn't already. The thread pool isn't destroyed until your process ends.