Urgent: Asychronous I/O in Unix

Please tell me how to simulate asynchronous I/O in Unix.i.e
If I am using  normal
fread( void *buffer, size_t size, size_t count, FILE *stream);
 command in my program the calling Unix process will block until the transfer is complete.

In Win32 we have the option like this

BOOL ReadFile( HANDLE hFile,  // handle of file to read
               LPVOID lpBuffer,  // address of buffer                                 that receives data
               DWORD nNumberOfBytesToRead,  // number of                                 bytes to read
               LPDWORD lpNumberOfBytesRead,
                        // address of number of bytes read
              LPOVERLAPPED lpOverlapped
                       // address of structure for data );
If lpoverlapped is not NULL then
Here the lpOverlapped will be filled up by windows with some internal status info & my process will not block.Instead it will execute instructions written next to point where i made call to this command.
After some time if I want to test the status of my I/O I can use
BOOL GetOverlappedResult( HANDLE hFile,
       // handle of file, pipe, or communications device
                         LPOVERLAPPED lpOverlapped,
      // address of overlapped structure
                         LPDWORD lpNumberOfBytesTransferred,
      // address of actual bytes count
                         BOOL bWait
      // wait flag );
which will return the status of I/O.So I have no need to wait for I/O to complete.
Please give me ways to simulate similar Asynchronous activity in Unix.I do not think it should be impossible  to simulate above two API's using unix API.
Please send me any source code examples if you can.
Please provide some discrete solution.

Thanking in advance..
flower020397Asked:
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braveheartConnect With a Mentor Commented:
See the man pages for "aio_read" and related routines.
Use "man -k asynchronous" to discover a full list of related pages

aio_read combines all the arguments into a single structure but has similar information to the ReadFile routine.

aio_result can be used in a similar way to GetOverlappedResult.

Note that these routines are specific to AIX so if you port to a different flavour of UNIX you will need to take this into account. For instance, on Solaris the equivalent routines have no underscore and may have slightly different functionality.
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flower020397Author Commented:
Thanks for the help.
If you have written some sample source code  please send me.
It can be helpful for me.
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braveheartCommented:
Sorry. All I did was check the man pages.
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