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PurgeComm info  Overview  Group

The PurgeComm function can discard all characters from the output or input buffer of a specified communications resource. It can also terminate pending read or write operations on the resource.

BOOL PurgeComm(

    HANDLE hFile,

// handle of communications resource

    DWORD dwFlags

// action to perform



Identifies the communications resource. The CreateFile function returns this handle.
Specifies the action to take. This parameter can be a combination of the following values:




Terminates all outstanding write operations and returns immediately, even if the write operations have not been completed.


Terminates all outstanding read operations and returns immediately, even if the read operations have not been completed.


Clears the output buffer (if the device driver has one).


Clears the input buffer (if the device driver has one).

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.


If a thread uses PurgeComm to flush an output buffer, the deleted characters are not transmitted. To empty the output buffer while ensuring that the contents are transmitted, call the FlushFileBuffers function (a synchronous operation). Note, however, that FlushFileBuffers is subject to flow control but not to write time-outs, and it will not return until all pending write operations have been transmitted.

See Also


See also:

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