EnumProcesses function (psapi.h)

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

BOOL EnumProcesses(
  [out] DWORD   *lpidProcess,
  [in]  DWORD   cb,
  [out] LPDWORD lpcbNeeded
);

[out] lpidProcess

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

[in] cb

The size of the pProcessIds array, in bytes.

[out] lpcbNeeded

The number of bytes returned in the pProcessIds array.

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.

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 lpcbNeeded value by sizeof(DWORD). There is no indication given when the buffer is too small to store all process identifiers. Therefore, if lpcbNeeded equals cb, consider retrying the call with a larger array.

To obtain process handles for the processes whose identifiers you have just obtained, call the OpenProcess function.

Starting with Windows 7 and Windows Server 2008 R2, Psapi.h establishes version numbers for the PSAPI functions. The PSAPI version number affects the name used to call the function and the library that a program must load.

If PSAPI_VERSION is 2 or greater, this function is defined as K32EnumProcesses in Psapi.h and exported in Kernel32.lib and Kernel32.dll. If PSAPI_VERSION is 1, this function is defined as EnumProcesses in Psapi.h and exported in Psapi.lib and Psapi.dll as a wrapper that calls K32EnumProcesses.

Programs that must run on earlier versions of Windows as well as Windows 7 and later versions should always call this function as EnumProcesses. To ensure correct resolution of symbols, add Psapi.lib to the TARGETLIBS macro and compile the program with –DPSAPI_VERSION=1. To use run-time dynamic linking, load Psapi.dll.

For an example, see Enumerating All Processes or Enumerating All Modules for a Process.

CreateToolhelp32Snapshot

OpenProcess

PSAPI Functions

Process Information