Question

Briefly describe the Win32 EnumProcesses function. Explain its return type, functions usage, parameters, and parameter data types.

Answer 1

EnumProcesses function

Retrieves the process identifier for each process object in the system.

Syntax

BOOL EnumProcesses(
  DWORD   *lpidProcess,
  DWORD   cb,
  LPDWORD lpcbNeeded
);

Parameters

lpidProcess

A pointer to an array that receives the list of process identifiers.

cb

The size of the pProcessIds array, in bytes.

lpcbNeeded

The number of bytes returned in the pProcessIds array.

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

It is a good idea to use a large array, because it is hard to predict how many processes there will be at the time you call EnumProcesses.

To determine how many processes were enumerated, divide the pBytesReturned value by sizeof(DWORD). There is no indication given when the buffer is too small to store all process identifiers. Therefore, if pBytesReturned equals cb, consider retrying the call with a larger array.