PurgeComm function (winbase.h)

Article
02/22/2024

Discards 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.

Syntax

BOOL PurgeComm(
  [in] HANDLE hFile,
  [in] DWORD  dwFlags
);

Parameters

[in] hFile

A handle to the communications resource. The CreateFile function returns this handle.

[in] dwFlags

This parameter can be one or more of the following values.

Value	Meaning
PURGE_RXABORT 0x0002	Terminates all outstanding overlapped read operations and returns immediately, even if the read operations have not been completed.
PURGE_RXCLEAR 0x0008	Clears the input buffer (if the device driver has one).
PURGE_TXABORT 0x0001	Terminates all outstanding overlapped write operations and returns immediately, even if the write operations have not been completed.
PURGE_TXCLEAR 0x0004	Clears the output buffer (if the device driver has one).

Return value

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.

Remarks

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.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2003 [desktop apps \| UWP apps]
Target Platform	Windows
Header	winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll